>> we just kind of started -- >> there was something big going on there. >> i had no idea what we were getting into. >> it makes me think of indiana jones. >> one wrong turn can be your last. >> this really can't be happening. we didn't realize that there would be a predator. they say if you're feeling down it's time to saddle up. with a little love, trust, and respect these majestic creatures can emerge as loyal and gentle companions. for both horse and rider there's nothing like it. >> she transformed into this awesome horse handler. and she knew what she was doing and what she was talking about. >> if only romantic relationships were that simple. this is the story of a young woman so gentle, so vulnerable she may have understood what makes horses tick. but humans? a different beast indeed. >> this doesn't happen to people we know. it just doesn't. >> it was crushing. i cried. i cried for days. i still cry when i think about it. i'm not sure what type of person it takes to do that. >> oak ridge, tennessee, nestled along the beautiful clinch river, is an unassuming place with a big story. >> capital of the world, oak ridge, tennessee. >> they call it the secret city for its part in the manhattan project, which produced the first atomic bomb. oak ridge still prides itself on being a community that values science and education, and it's a good place to raise a family. this is where erin hevelin grew up. >> when erin was three weeks old, she joined our family as i afoster child. >> erin's mom. >> she was i atiny child. i think she was fine pounds three ounces when we got her. >> that's small. >> oh, we thought she was the sweetest little thing. our oldest girls were 16 and they carried her around. >> she was like their little doll. >> yeah. they loved her. >> laura and her husband officially adopted their little doll when she was 3. erin grew into a shy little girl, reserved around those she didn't know. but with the horses she cared for at the east tennessee riding club that was a different story. >> when i think of erin with horses, i think of her as a bigger -- she was very confident, she knows exactly what she wants and what she's going to do. >> erin's friend, abby gooch. >> but with people she was much meeker, much quieter. calmer. >> horses would always be erin's first love. but as she entered her teen years, a certain young man caught her eye. his name is jon corwin. >> what was it about you that could kind of break through to erin? because her mom says how shy she was and she was better with horses than people. so what was it about you? >> i guess it's my charming personality. i have no idea. it still surprises me today. >> really? >> yes. i guess that i was always able to talk to her, figure out what she was feeling. >> erin's parents had strict rules about when she could start dating. >> we were those parents. we were the mean parents. >> jon was sure to get their blessing first. >> i ended up driving over to her parents' house and asking if i could have a date with their daughter. >> that's very chivalrous of you to go to her parents. >> that's the way i was raised, you that always get the parents' permission before anything. >> after graduating from high school jon joined the marines. he asked erin to marry him when he was just 18 years old with an unusual proposal. there was no champagne, but there was a cup of sprite. >> hands were clammy and everything, nervous as heck. and so i go to the sprite, put the ring on top of it and asked her to marry me. zwlt ring was around the straw. did she see it right away? >> no. i told look at your drink. >> what was her reaction when she finally looked down? >> she was crying tears of joy, ecstatic and just screaming "yes, yes, yes, i would love to." zblern's mom had heard that being a military wife comes with sacrifice. >> i'm a marine corps wife myself. and i know that it can be a very lonely life for people. and it's not easy. did you try to warn her? >> oh, yes. >> and did she listen? >> "i know, mom. i know, mom." you know, and of course when i was 18 i knew also. you know, you probably couldn't tell me a whole lot. >> the couple decided to elope to las vegas and tied the knot after a formal celebration known as the marine corps ball. >> my husband and i have had a lot of fun at marine balls. however, i never thought about getting married at one of them. why did you guys decide to get married there? >> because we were young. it was vegas. we honestly didn't plan on a lot of things. it was more like spur of the moment type deal, and that's how we lived. >> jon was assigned to the twenty nine palms marine base out in the california desert. in september of 2013 erin packed up for her move to join him. her mom saw her off at the airport. >> she's very directionally challenged, and she had two layovers. and i'm like, when you get off that plane you ask somebody where you need to go and you let me know as soon as you get there. >> what emotions were you feeling letting your baby go to start her new life? >> it was scary for me. you know, i knew that it was going to be harder than she ever dreamt. >> like any parent laura worried about her daughter finding her place in this new life. >> she's very shy. and i did have concerns about her making friends. we felt like base housing would be safer for her. because her husband was out in the field so often. >> it wasn't long before jon and erin learned they were expecting a baby. >> she was very excited. i was excited for her. >> sadly, her excitement was short-lived. in early 2014 she suffered a miscarriage. >> was it hard for both of you to hear that news? >> it was very hard. i was actually in the middle of a training exercise out in the field, and i received the message over the radio. my c.o. called me down to his vehicle and said that your wife had just had a miscarriage and she was in the hospital. so it was kind of shocking. and that night i drove back to the hospital and i met up with her and she was in tears. >> after she lost the baby, you know, part of me wanted to go out there and be with her. but i felt like they would do a better job of getting through their grief if they didn't have to worry about entertaining mom. >> wanting desperately to be a mother, erin vowed to try again. around four months later in june of that same year during a visit to the hospital for nausea the couple got good news. erin was pregnant again. >> here you are again. how did it feel this time? >> we were happy. but we were also fearful. afraid that it was going to happen again. >> were you cautiously optimistic? >> yes. >> she decided to wait to surprise her mom with the news. laura already had a trip planned to visit the following month. >> we had, you know, plans of just like going for walks. we were going to go to san diego to go to sea world and san diego zoo. but mostly just spend time together. >> you both must have been really wanting, needing this trip. >> absolutely. >> in anticipation of her mother's visit erin told her husband she was going to scout out some good hiking locations at nearby joshua tree national park. >> she had woke up and gotten dressed and gave me a kiss good-bye and said hey, i'm head heading out for the day and i love you. i told her i love you too and rolled back over and went to sleep. >> a routine good-bye. or so it seemed. until erin corwin vanished without a trace. coming up -- what had happened to erin? >> called her throughout the night. >> how many times would you say you tried to call her or tx her? >> at least 50 times. i was so stressed and worried. >> he said erin's missing. he said she left yesterday morning and i haven't seen her since. >> jon was concerned but withdrawn. when you have a spouse who's not extremely frantic you've got to question why aren't they super upset? we had a lot of questions for jon. >> when "dateline" continues. s jon. >> when "dateline" continues kim is now demonstrating her congestion. save it slimeball. i've upgraded to mucinex. we still have 12 hours to australia. mucinex lasts 12 hours, so i'm good. now move! kim, no! mucinex lasts 3x longer for 12 hours. 19-year-old erin corwin couldn't wait. her mom would soon be making her first trip to see erin and her husband, jon, at their new home in twenty nine palms, california at the marine base in the middle of the mojave desert. around 7:00 in the morning erin said good-bye to jon and told him she was coming here to joshua tree national park to scout out hiking trails for her mother's upcoming visit. jon expected her home that afternoon. but she didn't show. he tried her phone. no answer. >> did you keep calling? >> called her throughout the night. >> how many times would you say you tried to call her or text her? >> at least 50 times. i was just so stressed and worried. >> hours passed. and by the next morning jon was frantic. >> jon calls and he says erin's missing p. >> laura heflin got the call in tennessee. >> he said she left yesterday morning and i haven't seen her since. my first question was how much water did she have with her? >> you're thinking this is maybe a hiking situation. >> this is the child that has no sense of direction. you know, so i'm assuming she's lost. >> jon reported his wife's disappearance to the local police station. san bernardino county sheriff's department was soon notified. detective travis newport. >> obviously we were concerned, can we find her before something, you know, horrible -- before she meets a horrible end. you don't know if she's being held somewhere. we don't know if she's stranded in the desert still. >> laura's phone rang again. this time it was a deputy. he had another idea about what might have happened to erin. >> one of his first questions was do you think she's driving home? >> to tennessee? >> yes. >> maybe she's just left. >> yes. and i about laughed because i know how much she hates to drive, has no sense of direction, and there's absolutely no way she would give up a trip to sea world and the zoo. >> back at twentynine palms jon rounded up some of his marine buddies and headed into the national park. it's a vast expanse of nearly 800,000 acres of rugged rock formations, twisted joshua trees, and desolate open desert, where summer temperatures climb well past 100 degrees. >> we literally drove around joshua tree national park all day, trying to find any signs, any clues of where she might have been. >> do you see anything? any signs of her? her car. a piece of clothing. anything. >> nothing. >> there's a certain protocol detectives follow when investigating a missing person. start small and close to home. that inner circle of friends and family. the ones who know the person best. so when jon corwin reported that his wife, erin, had disappeared it was natural they'd look at him. >> so like with any investigation you start closest to the source of a missing person. so we had a lot of questions for jon. >> investigators learned that once childhood sweethearts erin and jon settled in twentynine palms things were far from perfect. >> their relationship wasn't intertwined. we knew that it was a relationship that was probably starting to dwindle. >> there was her miscarriage in early 2014. jon says it was heartbreaking and erin had trouble coping. >> she became very enclosed and depressed and would stay at home. and i'm definitely not the one that actually speaks out on his emotions. i've always kept them bottled up my whole life. she felt like i didn't care about it. and i did. it actually hurt me a whole lot. it really took a toll on our relationship. >> and erin's mom laura knew the young married couple also had money problems. >> we gave each of our kids a certain amount of money when they got married and they kept just buying things and all of a sudden i think that huge chunk of money was not there. >> you struggled with finances? >> definitely. the pay's not that great. but we had food on the table. we just didn't have any money for extracurriculars. >> was that hard for erin? i know there was an issue with her credit card. >> yes. it was hard. we ended up racking up debt. i ended up having to take away the card. >> times were lean? >> yes, very lean. >> they were grown-up problems for a couple barely out of high school. erin shared her worries with her friend abby. >> it's just hard to transition from being on your own to being married. sometimes a hard hand is what you need. and i think that's what jon was teaching her. and she didn't like it. >> detective newport and his colleague jonathan woods wondered about jon's behavior when his wife didn't return home. why did he wait a whole day to call police? >> it was a little suspicious that he waited till the next day to report her as missing. >> jon said he explained to the investigators he thought that was how these things worked. >> you see these common things on television now, you can't report a missing person until 24 hours they've been missing. and i truly believed that. >> made sense. maybe. but detectives noticed something. >> jon was kind of withdrawn. he was concerned but he was withdrawn. and at times we wondered is it his military background? you know, when you have a spouse who's not extremely frantic, you've got to question, you know-y aren't they super excited, why aren't they super upset? >> jon had gone into the park to search for his wife. sign of a concerned husband or something else? >> well, obviously as an investigator you have to wonder is this person trying to put themselves there? is this person trying to give us a reason why they would be there where the last person was seen or was possibly contacted? >> you were seriously looking at him. >> yes. >> i did think maybe jon. and i think that's normal. it doesn't make it right. but i think that it's normal human response to think the spouse. >> but really they might have been getting ahead of themselves. erin was missing and could well have run off on her own. there was no reason yet to believe any harm had come to her, much less that jon was responsible. there were other people to talk to and a new place to explore. a sanctuary for erin right here in the desert. one that would prove to be full of clues and secrets. coming up -- >> they were laughing and carrying on. >> anything flirtatious? >> giggly. i hadn't seen her act like that. it was like a kid in a candy store. i wasn't used to it. so it stuck out. >> erin, the shy young wife. compactly what kind of secret was she keeping? >> anytime you have a spouse who's missing and you hear that there might be some infidelity there, it's just human nature. not just as an investigator but as a human being to question whether or not that person might possibly be involved in the significant other's missing. >> when "dateline" continues. ♪ ♪ taking you back... ...since way back. freshness and softness you never forget, with downy. ♪ i'm a verizon engineer, part of the team that built 5g right. the only one from america's most reliable network. we designed our 5g to make the things you do every day, better. with 5g nationwide, millions of people can now work, listen, and stream in verizon 5g quality. and in parts of many cities where people can use massive capacity, we have ultra wideband. the fastest 5g in the world. this is the 5g that's built for you. this is 5g built right. only from verizon. when erin corwin went missing after a trip to the joshua tree national park, detectives started out by questioning her husband, jon. then they widened the circle, trying to learn as much as they could about her life at the marine base here in twentynine palms. they discovered that erin had been lonely when she first moved to the base, but quickly bonded with other military families. >> it was like kind of like "melrose place" in there. >> that's a perfect description of that apartment complex. >> everybody's friends. >> everybody's door is ten foot away from the next couple's door. >> reporter: erin and jon grew close with their fellow marine corps neighbors, including nichole and chris lee. a couple originally from alaska. erin's mom, lore. >> chris and nicole, and john and erin cooked out together all the time. i was happy, you know, that she had this. >> reporter: erin and nichole shared a common passion for horses. >> i was excited when erin and nichole met because nichole was into horses and i knew erin needed the horses. >> reporter: nichole introduced erin to the white rock horse rescue ranch and its owner, isabel megli. >> you're not very far away from twentynine palms, the marine corps base. >> no. 45 minutes. >> so is this not only a kind of a sanctuary for the animals, but maybe a little bit for the marine corps wives? >> yeah. >> reporter: isabel started the ranch in 2004. >> the spouses come to the ranch when their husbands or their fiancés or boyfriends are out in the field. they have nothing to do, most of them don't work, and they get very lonely. loneliness is probably the biggest problem that they have. >> this is where erin had her horse. >> yes. >> named -- >> cassie. >> cassie. and that was very special to her. >> yes, it was. >> come here, cassie. come here. hi. so you're erin's horse. >> she picked a horse that i would never have chosen for her. >> why? what was -- what was with the horse? >> the horse was standoffish. it didn't like anybody and it liked her. this horse was so bonded to her. and we couldn't believe it. >> reporter: before long, erin and jon, chris and nichole were spending more and more time at the ranch together. >> we'd go shooting, go out in the desert and shoot our guns. and we'd go up to the horse ranch and typical shenanigans. i had a little dune buggy that we'd all go take off-roading, while the girls were doing their horse stuff. >> reporter: isabel said when the couples were together, chris was always the life of the party. >> at the ranch chris was very funny. he was a real soft individual when he talked about his daughter, his wife, his family, but he also had the ability to be very stern. >> reporter: the ranch was clearly an escape for chris, who struggled after returning from deployment in afghanistan. >> there was something that -- you just stayed away from that subject. >> so he might have had a rough time overseas? >> yes, he did. he had a very hard time. >> reporter: but, said isabel, chris was a loving father to his and nichole's daughter, liberty. erin took to the little girl, too, and would help out her friends by babysitting the six-year-old. erin's mom says she was always good with children. >> gentle. very gentle. the younger kids at the barn. you know, they knew that she cared about them. >> reporter: so erin had found her place here, surrounded by friends and horses. but isabel said that around christmas of 2013 she started to see a connection between chris and erin. that seemed a little too close for comfort. >> they were laughing and carrying on about something on the computer. >> was there anything flirtatious about it or was it just too close for you? >> giggly. i hadn't seen her act like that. it was like a kid in the candy store. i wasn't used to it so it stuck out. >> reporter: isabel said she found the behavior so alarming she mentioned it to chris's wife, nichole. >> i said nichole, something's wrong. the way they're acting. she says no, no, there's nothing going on. she says they -- they connect. >> what was it that they could relate to each other about? >> she said they could relate to being sad. she said chris was sad. and that when he came back from the service he was a different person, and that he just wasn't himself. and erin could understand depression. she said they were just friends. >> reporter: but two months later nichole told erin's husband, jon, she needed to talk to him. and by then she was singing a very different tune about erin corwin. >> nichole had found out that chris had been having an affair with erin. i didn't actually get specifics at the time. >> you're totally clueless. >> yes. >> is this just a bombshell to hear this news? >> yes, it was a bombshell. it was earth-shattering. >> but jon says he still loved his wife and was committed to his marriage. >> i tried my hardest to make it work. >> were you in this for life? >> yes. >> this marriage? >> definitely. there's -- you should always try to fix something instead of just replacing it, and i was trying everything i could to fix it. >> reporter: he says that over time, he and erin reconciled. and even patched things up with chris and nichole. >> they started hanging back out with us. >> really? >> yes. >> you were able to accept them in, knowing what chris had done with erin? >> yes. it wasn't the same that it was before, but you always give somebody a second chance. >> reporter: or do you? erin was now missing. and the fact that she'd been unfaithful to her husband just added to investigators' suspicions about him. >> anytime you have a spouse who's missing and you hear that there might be some infidelity there involved, you're -- it's just human nature, not just as an investigator, but as a human being to question whether or not that person might possibly be involved in the significant other's missing. >> reporter: but then detectives found out something that made the potential pool of suspects a whole lot deeper. coming up -- >> it wasn't just your friendship slight infidelity. it was full-on, they were completely involved with each other. stunner number one, the secret affair with the neighbor wasn't exactly over. >> how betrayed did you feel? >> it was earth-shattering. it felt like somebody just stuck -- literally stuck a knife in my back. >> and stunner number two. >> this baby might not even be his? that's heavy stuff for someone to deal with. >> absolutely. jon realized that it was very likely not his kid. which again, that brings motive to a spouse. >> when "dateline" continues. ins i'll be observing your safe-driving abilities. play your cards right, and you could be in for a tasty discount. 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[ tires screech ] well, that came out of nowhere. shingles? camera man: yeah, 1 out of 3 people get shingles in their lifetime. well that leaves 2 out of 3 people who don't. i don't know anybody who's had it. your uncle had shingles. you mean that nasty red rash? and donna next door had it for weeks. yeah, but there's nothing you can do about it. camera man: actually, shingles can be prevented. shingles can be whaaaat? camera man: prevented. you can get vaccinated. baby, call the doctor. camera man: hey! you can also get it from your pharmacist! 50 years or older? get vaccinated for shingles now. i'm dara brown. here's what's happening. the biden administration has a message for migrants amid a surge at the southern border. the border is closed. homeland security secretary alejandro mayorkas tells the sunday talk shows they're expelling families and single adults but not young vulnerable children. and a 3,000-foot-wide asteroid passed earth by a range of 1 1/4 million miles sunday. nasa says there is no threat to our planet. it is the largest asteroid to fly by this year. now back to "dateline." detectives in san bernardino, california were working around the clock to figure out what had happened to 19-year-old marine wife erin corwin. they soon learned that erin had had an affair, and that made them suspect that her husband, jon, may have had something to do with her disappearance. >> some of the detectives thought that your behavior was strange, that you weren't acting sad enough. do you get why you were thinking that? >> i understand. i'm a very inclusive kind of person. i don't show emotions at all. >> did you worry at all, in the moment, that, "they're looking at me?" >> no, i did not. >> reporter: jon told detectives that his wife said the affair was over. he and erin had reconciled, and he'd even re-established his friendship with erin's former lover, chris lee, and chris' wife nichole. but in the first days of their investigation, detectives learned that erin's relationship with chris seemed to be going strong right up until the day she disappeared. >> it wasn't just your friendship, slight infidelity. it was full on. they were completely involved with each other. >> reporter: one of erin's close friends back in tennessee told investigators she talked and texted with erin nearly every day. erin, the friend said, was making plans for a life with chris lee. >> erin had expressed to this friend that she was going to get married to chris. >> reporter: the friend told investigators erin said that chris was taking her on a special trip the morning she disappeared and she'd texted her all about it. erin wrote, "so apparently this surprise trip is super important, and i finally got him to tell me it's by the national park." erin told her friend she didn't know what plans chris had in store. "yeah, i'm clueless. lol. i'm ready to know what it is. i mean, i have a couple ideas. i feel like it's big but yeah, lol, we shall see." the friend responded with a series of emojis, including a diamond ring, hearts, and question marks, suggesting, perhaps, an engagement? erin responded, "maybe!" and mentioned, "he was mysteriously playing with my ring the other night." erin added, "we shall see! this day cannot come quick enough!" and "it apparently takes two hours just to get there. a long slow drive. good talking time, though!" after erin went missing, that same friend spoke to jon. >> she had told me that erin had supposedly been out with chris that day and that she was expecting that chris was supposed to propose to her that day. >> how betrayed did you feel? >> it was earth shattering. i was -- it felt like somebody just stuck -- literally stuck a knife in my back. i was honestly ready to about strangle chris. >> reporter: but detectives soon learned something even more explosive. remember, erin had recently found out she was pregnant. she told her friend that she believed the father of her baby was her lover, chris, not her husband. >> did you think that the possibility existed that he did find out that this affair had not ended like he had thought and that this baby might not even be his? i mean, that's heavy stuff for someone to deal with. >> absolutely. that's why we wanted to question him so much. did jon realize that it was very likely not his kid? which again, that brings motive to a spouse. >> did you have anything to do with your wife's disappearance? >> no, i did not. everybody that knew me personally knew that there was no way i could do that. >> reporter: but jon says marines on the base who didn't know him well seemed suspicious. >> you could tell that they would look at me differently. i made sure i ended up staying home because of it. >> were you not able to do your job, then, if you didn't want to leave the house? >> no. at that time they considered me to be mentally unstable, and they took me away from everything pretty much because we handle firearms every day, and so i stayed at home. >> reporter: but now jon wasn't the only one on detectives' radar. if his fellow marine chris lee might be the father of erin's baby, and the person she was going to meet that day, then chris too might have a motive and an opportunity. >> did you look at both chris and jon as suspects? >> yes, absolutely. >> reporter: there was at least one other possibility. that erin, naive and just 19 years old, had simply decided to run away from her troubles. whatever happened, there was still no sign of her. that is, until this woman noticed something strange, something she had never seen before. >> i didn't know if somebody was doing drugs in there, or if somebody was just up to no good. and i knew that it wasn't supposed to be there. >> coming up -- a breakthrough new clue. >> as we were driving down the road there i noticed a car parked off to the left-hand side of the road that wasn't there the night before. >> there were shoe impressions, tire impressions. >> something had happened. >> i know my daughter. i couldn't get to twentynine palms quick enough. >> it must be excruciating. >> it was. the plane could not fly fast enough. >> when "dateline" continues. try our new scented oils for freshness that lasts. crafted to give you amazingly natural smelling fragrances, day after day... ...for up to 60 days. give us one plug for freshness that lasts. twentynine palms is definitely an experience to live out there. the desert is one of those places that you go out to find yourself and then after you've found yourself you're really happy to leave the place behind. >> reporter: debbie valek and her family lived just outside the marine corps base in twentynine palms, california. >> it's pretty barren. it's really flat. you can see for hundreds of miles in every direction. >> it was so remote in fact that a saturday morning donut craving meant an eight-mile drive to the nearest grocery store. so around 8:30 on june 28th, 2014 debbie and her daughter set off. >> we were going to go get donuts together and my daughter was all excited. >> they took their typical path into town via ranch road. >> and as we were driving down the road there i noticed a car parked off to the left-hand side of the road that wasn't there the night before. >> debbie said it was extremely rare to ever see cars parked near their home in this desolate stretch of desert outside the national park, a full five miles from the entrance. >> i thought it was odd, because there was no reason for it to be there. there's no hiking trails near my property. there's nothing to do out there. and if you don't live out there there's no reason for the car to be there. >> about 30 minutes later on their return drive from town, debbie said she was surprised to see the vehicle still sitting there. >> and i decided to drive up behind the car and take some pictures with my cell phone. >> from inside her truck she took three photos of the back of the car. >> i didn't want to get out of my truck because i didn't know what was inside the car, and who it belonged to. she had no idea at the time how important those photos would become. debbie and her daughter went home, enjoyed those donuts and got on with their day. she said she thought about reporting the car to police, but. >> i think i thought my imagination was just getting the better of me, and somebody had probably parked it out there with good reason. >> reporter: so there it sat. until two days later. 9:00 a.m. monday, june 30th. debbie and her family were eating breakfast when, to their surprise, they heard choppers overhead. >> i guess it dawned on me at that moment that i probably should have called the police because you could tell there was something big going on there. >> reporter: someone else had called police, who quickly determined the abandoned vehicle was erin corwin's. debbie's photos showed it had been there for two days. since the morning erin disappeared. what's more, next to erin's car, detectives noticed tire tracks and shoe prints. >> those tire impressions made what appeared to be a loop back towards the vehicle, erin's vehicle. and there were shoe impressions that appeared to walk from the driver's side of erin's vehicle to those tire impressions that came through that area. >> reporter: it appeared to detectives that erin had driven to this spot, and possibly switched into another car and gone off. >> i realized at that point that we were dealing with a situation where we're being led into one direction, which is the joshua tree national park. whereas in fact now her car is several miles north of that location. so i'm obviously very concerned that we hadn't been searching the right area. >> that's a daunting task. joshua tree national park is huge. and then now you're adding on this new area. is it like finding a needle in a haystack? did it feel like that? >> it's like finding a needle in a thousand haystacks. >> reporter: when erin's mom heard about the car, her mind went to the worst possible place. >> when they found her car without her, that's when i knew something else had happened, and i think at that point in time i knew she was not with us anymore. >> you knew. >> i knew. >> just from the car? >> yeah. i know my daughter, and it was just -- i couldn't get to twentynine palms quick enough. >> what's that like getting on a plane, you've had this revelation, the worst kind of revelation, and there you -- >> you have to turn your phone off. you know, you're, you can't get any communication until you get back on the ground. i mean, it was -- >> must be excruciating. >> it was. the plane could not fly fast enough. >> reporter: but detectives had to keep an open mind. they had no way to know yet whether erin had run away, or gotten lost. or was the victim of a crime. >> we had to bifurcate the investigation. we had to turn it into a search and rescue mission, and a potential homicide investigation. one was to try and look for a live and well, hopefully, erin corwin. and the other was to work another angle whereas unfortunately we might be looking for a deceased erin corwin. >> reporter: whichever course the investigation took, they knew they needed to check out a key piece of information. erin had told her friend back in tennessee that she was supposed to meet up with someone the day she vanished. her neighbor, and lover, chris lee. deputies first knocked on chris's door the day erin was reported missing. >> christopher lee told the deputies the extent of any contact he had ever had with erin corwin was waving hi in passing in a hallway of the apartment complex. >> reporter: apparently that wasn't true, but it wasn't necessarily incriminating either. chris had every reason to downplay his relationship with erin. nevertheless, detectives knew it was time to talk to chris lee again. coming up -- >> we found her car. >> did you? >> he seemed surprised that we found the car. >> did he start to tense up after this reveal? >> yes. i could see him definitely more tense and his body. >> marine corporal chris lee prepares for battle. >> your tire tracks are there as well as her tire tracks. >> i was worried that if i told you guys i saw her car because of my previous relationship with her you would have automatically assumed i did something. >> it was just a very unusual wild story that he was telling me. >> when "dateline" continues. those who du more with less asthma. thanks to dupixent. the add-on treatment for specific types of moderate-to-severe asthma. dupixent isn't for sudden breathing problems. it can improve lung function for better breathing in as little as 2 weeks and help prevent severe asthma attacks. it's not a steroid but can help reduce or eliminate oral steroids. dupixent can cause serious allergic reactions including anaphylaxis. get help right away if you have rash, shortness of breath, chest pain, tingling or numbness in your limbs. tell your doctor if you have a parasitic infection and don't change or stop your asthma treatments, including steroids, without talking to your doctor. du more with less asthma. talk to your asthma specialist about dupixent. if your financial situation has changed, we may be able to help. now, simparica trio simplifies protection. if yoticks and fleas?uation has changed, see ya! heartworm disease? 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(door knock - phone rings) there he is. hey sir. remember when you recommended that i go with the general for my auto insurance, so i moved your desk into this janitor's closet? the mop smell is a constant reminder sir. i bet it is. turns out, you were right about the general. i just misjudged them based on their commercials. they're actually a quality insurance company that's been saving people money for nearly 60 years. so, i'm giving you the primo desk, next to the vending machines. oof, it's nuts in here. for a great low rate, and nearly 60 years of quality coverage - make the right call - and go with the general. i'm a verizon engineer, part of the team that built 5g right. the only one from america's most reliable network. we designed our 5g to make the things you do every day, better. with 5g nationwide, millions of people can now work, listen, and stream in verizon 5g quality. and in parts of many cities where people can use massive capacity, we have ultra wideband. the fastest 5g in the world. this is the 5g that's built for you. this is 5g built right. only from verizon. >> reporter: two days after erin corwin disappeared, chris lee sat down for a formal interview. >> was he being cooperative? >> yes, he was. >> how are you doing? >> reporter: detective daniel hanke was part of the team investigating erin corwin's disappearance. he wanted to know why chris didn't admit to police right away that he and erin were more than just friends. >> i didn't, uh, bring up mine and erin's thing because it didn't seem pertinent at the time. >> okay. >> reporter: but now chris began to open up. he said his relationship with erin started innocently enough. he was depressed after his 2013 tour in afghanistan. erin was someone he could talk to. >> i had, uh, confided in her, you know, that i was feeling suicidal, and you know, she's like, you can't be doing that stuff. you know, it's kind of like -- she was someone to talk to about stuff that i didn't want to talk to about -- with my wife. >> reporter: he said erin confided in him as well, a terrible secret, that she suffered physical abuse at the hands of her husband jon. >> she said her husband was beating her and choking her and, like, she was scared for her life. she'd say that he would choke her whenever, like, he would get mad. >> reporter: the way chris told it, erin's story of jon's abuse is what brought them together. >> i just, like, being in the state i was was like, okay, well i can fix this. and then, you know, broken pieces fix each other. so, we just kind of started developing a bond. >> reporter: chris said that bonding soon turned to love. >> when you told her that you loved her, did she tell you that she loved you? >> she did. >> reporter: remember, police had heard from a friend of erin's that she thought she was pregnant with chris's baby. but chris insisted the relationship had stayed pretty pg. >> okay, and how many times did you guys kiss? >> four, tops. maybe some, like, hands up and down while we were kissing, but nothing real heavy. >> okay. >> nothing under clothes or anything like that. >> okay, so clothes never came off? >> reporter: chris said they talked about running away together, but he didn't want to risk losing his daughter, liberty. >> and i told her, i'm -- i'm not going to put liberty through a broken home. we had bounced the idea back and forth. >> reporter: he said the affair ended abruptly when his wife nichole found out about it. chris also said that's when he learned a big part of his bonding with erin was based on lies. >> what did she lie to you about? >> she told me that her husband was beating her, and that she was afraid for her life. >> reporter: he said he never talked to erin again after that. but detectives had those text messages between erin and her friend back in tennessee, which seemed to show the affair was far from over. detective trevis newport confronted chris. >> so no reason at all why she would message people saying that she's planning to meet with you on saturday?. >> like, she very well could've overheard me and conor talking, or me and skylar talking. >> reporter: chris suggested erin had overheard his plans for a trip to the desert and, upset that she wasn't invited, lied to her friends, saying chris planned to meet her that day. >> i just don't think she ever got over the fact that we had to stop seeing each other. >> we all know cheating in the military, that that can be a dishonorable discharge. did you think that would be a possible reason why he didn't want to talk about it? >> yes. and it's not uncommon to see military personnel deny such a relationship because they know that it could lead to repercussions. >> reporter: still, they pressed chris on his whereabouts the day she went missing. he told them he'd taken a drive to joshua tree national park to hunt coyotes and that he'd shot his .22-caliber rifle four to five times at some rocks, and at one point he said he encountered another man with a gun. >> i'm not sure if the individual shot at me or if he was just, like, recreational shooting, but there was an individual out there with a handgun, and it was fired in my general direction. >> he was very descriptive about this guy and his clothing and where he was out on a ridge line and, you know, that he was reloading and he fired, you know, four rounds at him. >> i got kind of lost, and at one point in time i came out. uh, followed gold crown road to old dale mine road, and then followed that to the road that comes out of the national park, and came home that way. and then i got home about 3:30. >> it was just a very unusual, wild story that i thought he was telling me. >> reporter: so detective hanke tried to shake chris up with new information. >> we found her car. >> oh, did you? >> yeah, it was parked in that area. >> okay. >> he seemed surprised that we had found the car. >> did he start to tense up after this reveal? >> yes. i could see it -- definitely him more tense in his body. >> reporter: and then hanke tried bluffing. >> your tire tracks are there, as well as her tire tracks. and your tire tracks drove over hers, showing that you met her there. >> but you didn't know for sure. >> i didn't know for sure, but i had a suspicion. >> reporter: under pressure now, chris changed his story slightly, saying that while he didn't see erin the day she disappeared he did see her car. >> i was worried that if i told you guys i saw her car because of my previous relationship with her you would have automatically assumed i did something. >> reporter: that didn't ring true to hanke, and his ears perked up even more when chris said this. >> did you make any other phone calls when you were out? >> no. i couldn't. i literally lacked the ability to because of the area we were in. >> you heard that word -- >> yes. >> we. >> yeah, that was a big tell for me. he had told me this entire time he was by himself. >> reporter: detectives interviewed chris for nine hours and thought they'd caught him in numerous lies. but they didn't have proof he'd committed a crime or for that matter that anything bad had even happened to erin. so detective hanke drove chris home. >> anything telling from that car ride? >> yes. it was pretty chilling actually some of the questions he asked me. >> like what? what was he asking you? >> he asked me how good i was at my job and how good our detective team was. >> what did you tell him? really good? >> i told him we were very good. he asked me specifically how many bodies have we not found in the desert. >> this is a freaky conversation. >> yeah. >> reporter: it wouldn't be long before investigators heard another strange thing. this time from chris's wife, nichole, about something out at isabel megli's horse ranch. >> nichole told you that something was hidden in isabel's closet. >> yes. >> what was that? >> it was a rifle, a .22-caliber rifle. >> coming up -- chris lee's wife. >> extremely uncooperative. angry. just not what you would expect of somebody who's trying to assist in an investigation. >> a chilling warning. >> tell erin that if she ever had anything else to do with her husband she'd kill her herself. >> that is a very strong statement. and now very relevant. >> yes. >> did you have to consider her as a possible suspect as well? >> of course we did. hearing a statement like that obviously just raises all kinds of red flags. really makes you wonder did this person pay somebody to harm erin. >> when "dateline" continues. why choose proven quality sleep from sleep number? because quality sleep is scientifically proven to help improve your overall health and wellness. introducing the new sleep number 360 smart bed. the only bed that effortlessly adjusts to both of you. proven quality sleep, is life-changing sleep. so you're a small business, or a big one. you were thriving, but then... oh. ah. okay. plan, pivot. how do you bounce back? you don't, you bounce forward, with serious and reliable internet. powered by the largest gig speed network in america. but is it secure? sure it's secure. and even if the power goes down, your connection doesn't. so how do i do this? you don't do this. we do this, together. bounce forward, with comcast business. >> reporter: three days had passed since erin corwin told her husband she was going out to scout hiking locations in joshua tree narc partial, but there was still no sign of her, and so detectives turned their attention back here, the horse rescue ranch that seemed to hold so many secrets. >> erin corwin and jon, chris lee, his wife, they were all tied to that ranch. >> you conducted a search of the entire ranch -- >> yes. >> looking possibly for a body on the ranch? >> want just a body, we were looking for any piece of evidence we could. anything liking someone to erin's disappearance. >> i said she's not here. >> they followed every lead they thought might be possible and that's what they did. >> reporter: nicole told them she staffed a rifle in isabelle's closet. >> you had no idea it was there? >> no idea. >> reporter: it was the .22 caliber rifle that erin told him he took to the park the day erin went missing. >> i was disturbed and i can't imagine someone hiding something in my house and not telling me. so i'm starting to get more angry at chris and nichole because now i'm part of it, and i didn't even know i was part of it. >> and you don't allow guns here? >> no, i don't. >> reporter: now she told detectives the day erin disappeared she received a text from nicole and chris saying she wouldn't be at the ranch that day because she was sick. the next morning chris and nichole were back at the ranch. by then, isabel had received a call that erin was missing. >> i kind of blew it off because i couldn't believe it. they'll find her. >> isabel noticed things were tense and she had nothing good to say about her missing friend. >> nichole was telling me that erin is probably hiding out somewhere to make chris' life miserable. she's setting us up. she's trying to hurt our family. erin's doing this just to get even. she's trying to get sympathy. >> reporter: chris was about to be discharged from the marines and planned to move back to alaska. detectives searched the suv and found a potato launcher like this one, a homemade cannon that shoots chunks of potato and other offices. >> the officer said you didn't know that's a weapon? i said i had no idea it was even in my car. >> a weapon, as it happens that was legal in california. detectives were suspicious of chris and now they used that potato launcher to get leverage on him. >> this patio we're sitting in is where chris was arrested? >> he was handcuffed to a chair. >> reporter: the charge? possession of a destructive device. chris had already spoken to detectives at length, but now that he was under arrest, isabel noticed that nichole seemed to be getting nervous and she started to say some odd things. >> she was very concerned that he would get his story confused because he wasn't in control of the facts as much as she was. >> detectives had already noticed nichole didn't seem interested in helping to find her friend erin. >> extremely uncooperative, angry, just not what you would expect of somebody who is trying to assist an investigation. >> reporter: isabel told them chris and nichole had also searched the internet, for some very specific information. >> they had researched how to -- how to dispose of a body, a dead body. she said that -- we've watched enough of those csi movies to know, no body, no case. >> reporter: remember, it was nichole who told jon about the affair. according to isabel, nichole said that she then confronted erin. >> it was very important for her to tell erin that if she ever had anything else to do with her husband she'd kill her herself. >> given that erin has disappeared, that is a very strong statement, and now, very relevant. >> yes. >> did you have to consider her as a possible suspect, as well? >> of course, we did. hearing a statement like that, obviously just raises all kinds of red flags. >> nichole lee had an alibi. detectives learned she was at home with her child the day erin disappeared, but even if she wasn't out in the desert that day, investigators believed she still could have played a role in arranging erin's disappearance. >> it really makes you wonder, you know, did this person pay somebody to harm erin? >> reporter: erin's mom lore had suspicions of her own. in those initial days following erin's disappearance, lore stayed at erin and jon's apartment on the base. >> i went for a walk, and i'd come back and nichole's sitting on their walkway and if looks could kill. >> towards you? >> towards me. >> must have been an odd moment. >> i guess it, for some reason, didn't surprise me. >> reporter: instead of shrinking, the suspect pool seemed to be growing. but there was still no proof any crime had even occurred, except maybe possession of a potato gun. chris bailed out on july 5, 2014, one week after erin disappeared. two days later he was officially discharged from the marines and the lees returned to alaska. >> people kept having a fit because they let him go to alaska. >> reporter: meanwhile, detectives in san bernardino continued to hunt for clues, as to where erin corwin might be found. and they learned something that would launch them on a massive, treacherous search in the desert. coming up, danger in the heart of the desert. >> it makes me think of "indiana jones." >> what would investigators find? when "dateline" continues. when . frontline® plus kills fleas, ticks, and chewing lice, and its fast-acting, waterproof formula protects for a full 30 days. with frontline plus, and new frontline shield for dogs with tick and mosquito repellency... you and your pet can go everywhere. ♪♪ ♪♪ no matter how you define it. frontline®. here. there. everywhere. ♪♪ introducing the new sleep number 360 smart bed it's the most comfortable, dually-adjustable, foot-warming, temperature-balancing, proven quality night's sleep we've ever made. don't miss our weekend special. save $1,000 on our most popular smart bed and adjustable base. plus, 0% interest for 60 months. ends monday. was erin corwin still alive somewhere in the desert or was she the victim of foul play? this is a huge operation trying to find erin corwin. >> yes. >> we had hundreds of searchers from four different counties. >> reporter: but with such an enormous area to cover the search dragged on. and in the withering desert heat, the odds of finding erin alive dwindled. her parents had long ago returned home to tennessee. >> it must have been so hard getting on that plane. >> it was. >> there was any part of you that felt like, of course it's reasonable, but did you feel guilt or -- >> oh yes. yeah. you're right. >> "i shouldn't be leaving," or, "what if they find her tonight or tomorrow." >> right. >> reporter: the investigation had narrowed in one way. detectives cleared erin's husband jon of any wrongdoing in connection with her disappearance. cell phone and computer records showed jon was on the base the entire day that erin went missing. they also concluded chris was lying when he claimed jon had been abusive. >> over the period of the investigation jon was interviewed multiple times. jon submitted to a polygraph test. i mean, easily 20 hours total we had spoken with jon. >> did he pass the polygraph? >> yes. >> i knew what was true, and i gave them my honest answers. and i never lied to them, and the light shined through. >> reporter: but chris lee had lied to them and seemed interested in how to dispose of a body. and isabel told them he'd taken a trip to the desert with a friend the week before erin disappeared. >> and he says, "we found a lot of mines. he said i found this one mine, no one will ever find. >> reporter: detectives believed it was all adding up. chris killed erin and then dumped her body in a mineshaft. so they decided to start searching, but here was the problem. the mojave desert is pockmarked with hundreds of mineshafts. detectives knew they needed help. >> the search-and-rescue folks explained that there was a guy who knew a lot about the desert, knew a lot about the caves, you know, would be a great resource to us. >> reporter: this is the man they were talking about, doug billings. "cave-doug" to his pals. as much desert rat as the gold miners who used to roam the mojave a century ago. but instead of a pick axe and a mule, he's outfitted with gps and a hummer. >> i've been down every one of these mines, including the one we're standing in front of right now. i know how deep they are. i know what's inside 'em. >> when other kids were playing little league billings was hanging off a rope catching rattlers. by the time he was an adult billings was traveling the globe, exploring the underworld. but the mojave is his home. so detective newport and billings started talking and a relationship quickly formed. >> almost every day, doug and i would talk on the phone, and he would send me photographs, aerial images, satellite images, and say, "check these mineshafts. you know, these are more that i have located. >> just getting to a mineshaft could be an ordeal as we discovered. billings took us out to one of the high priority search areas but the road got so rugged and treacherous, we were forced to leave behind our s.u.v, along with two members of the crew, and carry on in billings hummer. >> this is really hard to get around. >> yes, yeah. >> i mean, this is, sort of, at times, white knuckle driving. >> yeah, there -- >> i have to admit. >> i mean, you look straight down, you don't wanna make one wrong little turn. >> yeah, yeah, one wrong turn can be your last turn. >> this is one of the mines that was searched? >> yes. >> reporter: billings and the other volunteers checked off one dangerous mineshaft after the next. >> we're monitoring the oxygen. so it's all clear. the next step we do is we always throw in a little bit of rocks. and you listen quietly for a rattlesnake. it's, kind of, a general protocol. this part of the desert, they love to come and hide out in these mines -- >> it's cool in here -- >> to get out of the sun. yeah, you see the temperature drop. and, as we walk in here, click your light on. >> oh, that could be scary if it dropped down. >> yeah. yeah, so this could be a false floor here. we'll stay on this side here. >> it makes me think of "indiana jones," kind of the drop. >> yeah. i've seen those in real life. >> reporter: these are the most dangerous shafts to search, vertical ones that go straight down into a crumbling abyss. >> originally we were dropping mine shafts. we were physically going down the shaft. we would rig the ropes, rappel in, check it, clear it. and move on. but it became not feasible with the amount of mines we had to search. >> reporter: so they outfitted buckets with cameras. it sped up the process, to be sure, but with hundreds of mines to explore the search dragged on for days, then weeks. detectives were aurn side by side with the hundreds of searchers looking for erin. >> we were digging holes, we were searching. we wanted to find her, so we were doing everything we could to help. >> reporter: and yet, there was no sign of erin corwin anywhere. no clothing, no footprints, nothing. but then detectives caught a break. remember that trip chris took with a friend to look at mines? turns out, chris's friend had taken pictures. detectives obtained the photos, and seven weeks into the search showed them to "cave doug." >> without skippin' a beat, mr. billings almost immediately began identifying each photograph and we began plotting them on the topographical map. >> the first picture they showed me was the mine across here. immediately recognized the tower. they showed the shaft, going down the shaft. i recognized that. second, they showed me the cabin and then the next picture was of, actually, the mine we're standing next to. >> reporter: so they bet on billings' memory and focused their efforts here. around what's known as the rose of peru mine. >> around the rose of peru mine are hundreds of other abandoned mines like this one. and anyone of them could have been a potential burial site. >> reporter: investigators had high hopes they were finally targeting the right area. but after an exhaustive and expensive search that lasted for weeks and weeks, they decided this was it. saturday, august 16, 2014, would be the last day of the search. >> we felt we had one more shot at it. >> reporter: in the early evening they headed for the very last mine on their list. >> and as nighttime falls out there, you don't want anybody out there still, so we began to really collect our thoughts and decide, any minute now we need to start calling the search. >> a member of the san bernardino cave rescue team, a doctor in fact, came upon this mine and right away noticed a strange smell. >> it was the stench of gasoline. >> reporter: there was also a shell casing resting near the mouth of the mine. the searchers lowered a bucket cam. >> we received a phone call from one of the satellite phones that was out there with the search team and they could see what appeared to be a leg or some sort of a body part down at the very bottom of the mineshaft. >> that is unbelievable that this search was minutes away from being called off, after weeks and weeks, and you find something. >> yes. it was very unbelievable. >> reporter: a full exploration of the mine would have to wait until daybreak. >> detective hanke, he called me at roughly 9:00 or 10:00 that night and said that we had found a body at the bottom of this mine shaft. >> did you sleep at all that night? >> i did not. no. coming up -- >> i had no idea what we were getting into. do i want to put my life in danger? >> reporter: josh journey to the bottom of the mine, when "dateline" continues. bottom of the mine, when "dateline" continues since 2009, we've lost 33 million acres of grassland and wildflower habitat in the us great plains. air wick scented oils is partnering with world wildlife fund to reseed 1 billion square feet of native wildflowers and grasslands... making our connection to nature stronger. learn more at airwick.us these are real people, not actors, who've got their eczema under control. with less eczema, you can show more skin. so roll up those sleeves. and help heal your skin from within with dupixent. dupixent is the first treatment of its kind that continuously treats moderate-to-severe eczema, or atopic dermatitis, even between flare ups. dupixent is a biologic, and not a cream or steroid. many people taking dupixent saw clear or almost clear skin, and, had significantly less itch. don't use if you're allergic to dupixent. serious allergic reactions can occur, including anaphylaxis, which is severe. tell your doctor about new or worsening eye problems, such as eye pain or vision changes, or a parasitic infection. if you take asthma medicines, don't change or stop them without talking to your doctor. so help heal your skin from within, and talk to your eczema specialist about dupixent. if your financial situation has changed, we may be able to help. if your financial situation has changed, i'm a verizon engineer, part of the team that built 5g right. the only one from america's most reliable network. we designed our 5g to make the things you do every day, better. with 5g nationwide, millions of people can now work, listen, and stream in verizon 5g quality. and in parts of many cities where people can use massive capacity, we have ultra wideband. the fastest 5g in the world. this is the 5g that's built for you. this is 5g built right. only from verizon. i'm dara brown. here's what's happening. miami beach is extending emergency restrictions due to spring break crowds. a curfew is in effect from 8:00 p.m. to 6:00 a.m. the rules stay in place until april 13th. a major league broad cast game will be broad cast from the site of the movie "field of dreams." the new york yankees will play the chicago white sox. it has a capacity up to 8,000 fans. now back to "dateline." ♪ ♪ >> reporter: a massive search effort that once spread across 2,000 square miles of desert was now focused on a single 4 x 6 foot hole. >> i had no idea what we were getting into. >> reporter: paul anastasia and brenton baum are with the san bernardino county fire department's elite urban search and rescue team. >> i was told they had found a body, approximately 140 feet in a mineshaft. >> reporter: but there were problems. >> they detected propane and gasoline fumes. >> reporter: that's why they were called. they're trained to work in tight spaces. they risk their lives regularly to rescue people in great danger. but in this case, taking a risk to recover a dead body gave them pause. it's risk versus gain, do i want to put my life in danger? >> after talking it over and knowing how important their efforts could be in solving erin's disappearance, they agreed to go. bob who is admittedly claustrophobic, got the short straw and started deskrenldzing down. >> it was 100, 140 feet, deeper than i've ever been. >> how deep was it? >> it was eerie, rock collapsing, snakes, and also just the heat. it was 110 degrees topside, and i believe it was about 90 downside. so work in that environment, you only have a limited amount of time effectiveness before you're quickly fatigued. >> what did you see? >> a -- sprite bottle -- a rope -- a tire down there propane tank -- some plastic jugs -- a lot of rock and rock debris -- some railroad ties. >> reporter: and then he saw it, a human body. that sounds like out of a horror movie. i mean, to hate to say it like that, but to rappel down and see a decomposing body. >> we see a lot of death in this line of work. over time you just develop a method where you just ignore your emotions for a little while. and you just focus on the task you need to do. and then, you know, face up with your emotions later. >> reporter: baum first took photos while suspended above the grisly crime scene. then methodically set about gathering evidence and sending it back to the surface. >> the original plan was for me to do the whole operation, but i had been down there about 45 minutes and was pretty fatigued. so our captain made the decision to go ahead and rotate us out. >> how did you feel when -- when you finally got out of that snin >> i took my mask off, i was hit with the smell all of a sudden, what i -- what i had been immersed in and didn't smell in the shaft, i smelled on the topside, 'cause it was all saturated in my clothes. i started dry heaving. >> reporter: then it was anastasia's turn. his assignment? get the body. >> i would be lying if i said i was excited about going down into that mine shaft. i never put a body in a bag. >> reporter: once in the mine, anastasia realized retrieving the body was going to be far harder than expected. >> i did a little assessment with my flashlight. and i -- i realized that that was a false bottom. and then i got a little more concerned with some rocks coming down and knocking out that false bottom, or loosening it up. >> 'cause then -- everything would be gone. >> yeah. i had no idea how deep that shaft was. >> reporter: so, suspended in mid air, anastasia began placing the body in the bag without disturbing the false bottom on which it rested. once that was done he found something else. saz torch in the corner of the mine. >> had it been lit? >> it-- it didn't look like it had been lit to me. it looked like it was brand new. like it -- someone had just made it. >> ever so carefully, anastasia made his way back up the mine shaft with the torch and with the body. back on the surface detectives made a positive i.d. after eight weeks of searching, on the day they'd decided would be their last, they had finally found erin corwin. >> all these hours we had worked, just thinking deep down inside, she's got to be somewhere in one of these last caves, she just has to be. and then having that confirmed, just overwhelming emotion. >> a few minutes before midnight, the phone rings again. wakes us up, and it's detective dan. and he says, it's her. it's like, "this really can't be happening to us." you know? "not that child." >> reporter: the cause of erin's death? possible blunt force head injury and apparently, strangulation with a sinister tool. >> the pathologist discovered what's known as a garrote. i was unfamiliar with that at the time, but i quickly learned what that was. it was a parachord with two rebar handles, and it encircled her neck. >> reporter: isabel from the horse ranch said nichole lee once told her, "no body, no case." now detectives finally had the body and soon they had an arrest warrant. the charge: murder. coming up -- >> ladies and gentlemen, at its core this is a very simple case. >> reporter: an accused killer on trial. when "dateline" continues. " con. the general for car insurance, so we left you deep in the woods? turns out you were right about the general. they're actually a quality insurance company. let's get out of here. five more minutes, my skunk is almost done. for a great low rate, and nearly 60 years of quality coverage, go with the general. still fresh... unstopables in-wash scent booster. for a great low rate, and nearly 60 years downy unstopables. ladies and gentlemen, at its core, this is really a very simple case. >> reporter: october 2016. 2 1/2 years after erin corwin's death. a jury gathered in this san bernardino courtroom. the person on trial -- chris lee. the charge, first degree murder. >> all of the evidence in this case points to one person. one person who prepared, planned, studied and executed the murder of erin corwin. >> there was so much connecting him out this at that mineshaft, even the very location of that particular mine, that tied him to the crime, that for him not to have done it, it would be the unluckiest man ever. >> reporter: the prosecutor used friends and family of the lees and corwins to lay out the case against chris. several people who knew chris, including this fellow marine, testified he had shown a lot of interest in how to dispose of a body. >> he did mention the benefits of hiding a body in a vertical position so ground penetrating radar wouldn't be able to see the outline of the body. >> reporter: former downstairs neighbor and one-time friend, aisling malakie also took the stand. >> how many times prior to june 28th did you hear the defendant talking about murder? >> more than i can count. >> reporter: aisling also told the jury about chris's wife nichole's odd and cold response when she heard erin was missing. >> i called nichole and said, "where's your husband? there's people here looking for her, you know. erin's missing." she replied with, "i don't care what happened to that little bitch." and she laughed at me and told me to mind my own business. and then, i hung up on her. >> reporter: an her husband, connor, testified he saw chris lee around 6:00 the morning erin disappeared. and in the back of his jeep, he noticed something. >> i saw a bunch of items covered by a tarp and i saw a white propane cylinder. >> white propane cylinder? >> correct. >> like -- for a barbeque? >> yes. >> reporter: conor said the propane tank he saw in the jeep looked like the one recovered from the mine. >> i asked him why it was in there and what he was planning on doing with it. >> what was the defendant's response? >> that he was going to blow up a mine shaft with it. >> reporter: isabel megli from the horse ranch told the jury she also recognized the tank pulled up from the mine. she said chris had borrowed it from her the day before erin disappeared. >> i asked him if he was going to have a barbecue. >> and what was his response? >> he said "no." he was going to use it to play games. >> did the defendant ever return the propane tank? >> no. >> reporter: and detective woods testified that a search of the suv chris was driving at the time of his arrest yielded another piece of evidence. >> that is the garrote that was located underneath the front passenger seat. >> i'd only seen one of those in my life, and that was the one that was wrapped around ms. corwin's neck. and for the second time in the same week, i saw the second one. >> reporter: and there was another link to chris, that shell casing found near the mouth of the mine shaft. it matched chris' rifle. the jury also got to hear from erin's confidante back in tennessee. jessica trentham was erin's close friend and secret keeper. she's the one who told detectives everything she knew about erin's affair with chris. >> did she tell you how she felt about christopher lee? >> she made it known that she loved him more than her husband. >> reporter: jessica said erin had plans for a future with chris. >> she stated that she believed she would be divorcing her husband or that a divorce would come and that she was hoping to be able to stay with him. >> reporter: she said chris told erin he had a special trip planned for her the weekend she disappeared. >> she said that he was going to surprise her with -- a trip out to the desert. >> how did she sound? what was her feelings about that? what did she sound like to you? >> she was excited to get to spend time with him. >> reporter: jessica also testified about a text she got from erin, "my mother comes in a week. i'm excited!" jessica responded, "are you gonna tell her?" >> what did -- what did you mean when you sent the text, "are you gonna tell her?" >> that she was pregnant. >> reporter: erin texted back, well, chris wanted to tell everyone next week, on june 28, 2014, jessica spoke to her friend for the last time. at 7:19 a.m. california time, erin called jessica back in tennessee. >> she said that she was getting ready and about to leave the apartment. to go meet chris to have their special date. >> did -- what was your response to that? >> i was excited for her. >> why? >> i wanted her to be happy. >> did you make plans or talk about things? >> she was supposed to call and let me know how it went. >> did you ever get that phone call? >> no. >> do you think she was planning to start this new life with him? with the baby -- >> seems -- seems so. >> it seems so. it was really hard to hear that. i think one of the harder things is to know that she was going through all that and she did not share it. it just makes me wonder the level of his manipulation because obviously he was leading her on. >> reporter: but perhaps the most damning evidence came from this dna expert, who analyzed the items that were pulled out of the mine shaft where erin's body was recovered. >> in this case, i chose to go with more substantial testing. >> reporter: remember that homemade torch? it consisted of a piece of wood with a green t-shirt wrapped around one end. and on the shirt's collar, dna. >> in this particular case we have a major dna profile which includes christopher -- uh, christopher lee. >> there was also dna around the mouth of the separate bottle found in the mine. >> i have a mixture of two individuals. uh, christopher brandon lee and erin corwin. >> reporter: erin and chris, it appeared, had been sharing a sprite that day, the same drink her husband had once used to propose marriage. >> i think he took her out to the desert that day to kill her, because he was a hurdle for the rest of his life. by the end of this investigation, we realized chris didn't care about anybody but himself. >> reporter: the prosecution said chris took erin out to the mine, strangled her and dropped her in. he may have intended to use the propane tank and torch to blow up the mine and conceal her body, although he apparently didn't follow through. their conclusion, it was a carefully-planned, cold-blooded murder. the evidence seemed overwhelming, but now it was the defense's turn and jurors were in for a surprise. chris lee was about to testify, and no one was prepared for the dark tale he would tell. coming up -- a story from the stand that stuns the court. >> i couldn't live with myself if i kept this a secret any longer. >> when "dateline" continues. longer >> when "dateline" continues ugh, there's that cute guy from 12c. -go talk to him. -yeah, no. plus it's not even like he'd be into me or whatever. ♪♪ ♪ this could be ♪ hi. you just moved in, right? i would love to tell you about all the great savings you can get for bundling your renter's and car insurance with progressive. -oh, i was just -- -oh, tammy. i found your retainer in the dryer. i need to tell the truth. >> reporter: chris lee, a husband, father, and decorated marine, would be the first and only witness in his defense. his attorney took chris through his version of events. >> i couldn't live with myself if i kept this a secret any longer. >> reporter: by june 2014, chris was preparing to leave the marines. he told the jury that he knew it was time to end his relationship with erin. >> did you have any plans after leaving the corps? >> yes. me, nichole, and liberty were planning on -- moving back up to alaska. >> had you told erin this? >> i did. >> reporter: chris said that he had planned a hunting trip, and that he had invited erin along so they could talk. >> was it just gonna be you and erin? >> no, it wasn't. >> reporter: chris had asked two friends to join him, including his neighbor, conor. >> why were you inviting all these other friends of yours, if you needed to talk to erin? >> because i didn't really wanna have lengthy conversations. so i wanted to be able to go hang out with my friends, and actually do some hunting. in case the conversation got too deep or became to the point where i was uncomfortable with it. >> reporter: but chris said by the morning of june 28th, he found out his friends had bailed. so he and erin set out for the park, just the two of them. chris had a propane tank and, he said, he wanted to blow off some steam -- literally. >> had you told erin that you were going to actually try to blow up this mine? >> on the way there. >> do you remember what her reaction was? >> she wasn't happy about it. she thought it was stupid, unsafe. you know, she thought this trip was gonna be about us talking. and i told her that it was but, you know, that i wanted to try and do this, too. >> reporter: when they arrived, chris began unloading his supplies. >> i took the tires out of my jeep, and i tossed them down the mineshaft. >> what was erin doing during this time? >> she was sitting in the jeep, listening to music. she didn't wanna be near any of this. >> all right. so what did you do next to blow the mine? >> i went to the back of the jeep to grab my torch. and i realized i had not doused it in gasoline. >> reporter: feeling frustrated, chris said, he returned to his jeep. >> we started having a conversation. >> about what? >> about plans. she wanted to come to alaska. she wanted to be part of liberty's life. i had told her, you know, i -- i didn't want that. i told her, you know, i decided that, you know, you can't be a part of liberty's life. and she said that she wanted to, that she loved liberty, you know? and i told her, you know, it's not your choice. it's not your daughter. you don't get to love her. she's mine. >> what were you thinking at that point? >> i was thinking there was no reason for erin to love liberty. she's not hers. she -- she couldn't have any kind of emotional attachment to her. >> reporter: and then, chris said, he remembered something else. a story that would be central to his defense, and would stun this courtroom. he said he recalled something his wife had shown him one night when she was giving liberty a bath. signs, chris said, that nichole believed, showed sexual abuse. >> then she thought maybe erin had molested liberty. because she was uncomfortable with the way she was around her, when she had been watching her. >> what was your reaction to that? >> i felt so safe in my little community that i -- i didn't think it was possible. >> you didn't believe nichole. >> no, not at the time. >> reporter: but now, as they talked at the mine, he said erin seemed way too attached to liberty. >> when erin told me she loved liberty and that she wanted to be with her, you know, something clicked. it turned a gear in my head. and i said, "why do you care about liberty so much? why -- why do you wanna be part of her life?" and erin -- erin told me, you know, "i just -- i just love her." and i -- and i -- i stood up, and i stopped her. and i-- i said, "did you touch liberty?" and she reeled back a little bit and started stuttering over her words. and she was saying, you know, "i -- i --" and i stopped her again. and i yelled at her this time. and i said, "did you molest my daughter?" and she said, "yes. but --" and that was the last thing i heard her say. >> reporter: an explosive allegation, against the victim. >> did you worry that that could really turn off the jury? >> absolutely. but it was what chris insisted was the truth. erin's husband said it simply wasn't possible. >> she was nurturing, caring, never did anything illicit or crude or harmful. nobody that personally knows erin or has even heard of erin would believe that. >> reporter: and for detectives -- >> i personally felt disgusted. from all the people we've talked to that knew erin -- we didn't think this was even an angle that christopher lee would play. this came out of left field. >> reporter: but chris said, it was hearing what he believed to be a confession from erin that caused the horrible events he now recounted, in chilling detail. >> i -- i stumbled back. and i sat on the edge of my jeep and caught myself with my hands. and in my right hand, i felt the metal from the garrote. it -- it set me off. i just felt so much hate, so much rage. and i grabbed it. and i stood up and i came up behind her. and i put it around her neck. training took over then. and i turned around. and i started pulling. nothing would have stopped me from doing what i was doing. i told myself, while i was doing this, "never again." i wasn't gonna let anybody hurt my daughter again. i had let her into my daughter's life. it was my fault that my daughter was hurt. i just kept choking her. i don't know how long it was. might've been five minutes, ten minutes. it felt like forever. and i just kept choking her. and then the anger, that feeling of disgust and hate, ebbed a little bit. and i let go. and she dropped to the ground. >> reporter: christopher lee was describing for the jury how he had killed erin corwin. >> after a few minutes, my -- i realized what happened. i know i killed her. and so the garrote was still around her neck. so i grabbed it. and i dragged her to the edge of the mineshaft. and i pushed her in. >> reporter: his story accounted for all the physical evidence, and portrayed the killing as a crime of passion committed by an outraged father. but now the prosecution took over, and shocked the courtroom all over again. coming up, a heart stopping moment. >> you couldn't have stopped there, right? >> no. >> why not? >> nothing would have stopped me at this point. i was too angry. >> the fate of marine corporal chris lee. when "dateline" continues. ♪♪ i've always been running. to meetings. errands. now i'm running for me. i've always dreamed of seeing the world. but i'm not chasing my dream anymore. i made a financial plan to live it every day. ♪ there was a dream ♪ ♪ and one day i could see it ♪ at northwestern mutual, our version of financial planning helps you live your dreams today. find a northwestern mutual advisor at nm.com >> reporter: chris lee had shocked the courtroom, telling the jury that he did kill erin corwin, but it wasn't premeditated. instead, he said, he snapped when he claimed erin confessed he had been molesting his daughter. now the prosecutor cross examined chris, confronting him on those allegations against erin. >> you heard these accusations from your wife. so you didn't call the police? >> no. >> nicole immediately picked up and called the police? >> no. >> you're still having sex with a woman who your wife thought was molesting your daughter, right? >> yes. >> reporter: the prosecution's mission, show the jury that they could not believe chris. because he'd lied, claiming not to know where erin was through all eight weeks she was missing. >> people lie for a reason. it was important that i point out that he lies to protect himself. >> you had a choice to tell the truth? right? >> i did. >> and you knew erin had a mother? >> yes. >> you knew she had people that loved her? >> yes. >> you knew a lot of people were looking for her? >> yes, i did. >> you essentially made a decision to hold them hostage, right? >> yes. >> reporter: perhaps the biggest moment in court came when the prosecutor found a striking way to demonstrate how chris had killed erin. >> okay. so for the record, what you did is you put it around the dummy's neck that i'm holding, you twisted it around, and then you turned backwards? so you're actually back-to-back with her? >> yes, sir. >> okay. and you testified earlier that you pulled really, really hard? >> yes, sir. >> you could've stopped there, right? >> no. >> you couldn't have stopped? >> no. >> okay. you already made the decision to kill her? >> yes. >> and you were gonna follow through with that decision? >> yes. >> okay. >> my goal was to show the jury how long it takes to kill somebody like that and to show them the brutality of what was done. it's one thing to say, as he did on direct, "i strangled her and i pushed her down the hole." it's another thing for him to actually show us what you did. so i think the jury was entitled to see that. it was heavy. it was one of the heavier moments i've had in court. >> that's about ten seconds in. you could've stopped. right? >> no. >> twenty seconds in. you could've stopped? >> no. >> why not? >> nothing would have stopped me at this point. i was too angry. >> i saw the reaction of the jurors. it was pained. their expressions were pained. >> okay. so we're about 40 seconds in. you're still doing it? >> yes, sir. >> that's about a minute in. you're still doing it? >> yes, sir. >> and your testimony is you couldn't have stopped? you couldn't have just let go of those handles? >> no. >> a minute 20? still no, huh? >> no. >> okay. you can let go. can you let go now? >> yes, sir. >> and then you threw her down a mineshaft, didn't you? >> i did. >> like a piece of trash. >> i threw her down the mineshaft, yes. >> like a piece of trash? right? >> is that a question? >> yes. >> reporter: the jurors had heard a confession from chris lee. would they think it was voluntary manslaughter, a killing carried out in the heat of passion? or was it premeditated murder? the prosecutor made his final appeal to the jury. >> do you think the defendant testified to express remorse? ladies and gentlemen, if you do, you're mistaken. the defendant was not remorseful. he didn't care. he didn't care when search and rescue and homicide and fire departments are putting their life at risk looking for erin. he didn't care that he was holding her mother hostage. he didn't care one bit until it came time to talk to you. the people who are gonna decide what crime he's guilty of. >> reporter: defense attorney david kaloyanides asked the jury to consider this case as a tragic crime of passion. not one of premeditated murder. >> mr. lee was provoked. only you can decide whether that provocation was sufficient to justify a lesser included. not justify the killing because it wasn't justified, but was it murder? was it deliberate, willful, premeditated, lying-in-wait murder? or was it a tragic killing that shouldn't have happened? >> the jurors pondered those questions for just an hour and a half. then they reached a verdict. >> we, the jury, find the defendant christopher brandon lee guilty of first-degree murder. the defendant intentionally killed the victim by means of lying in wait. >> reporter: christopher lee was convicted on all counts. he will spend the rest of his life in prison without the possibility of parole. >> what was that moment like for you? that, that was pretty final, at that point. guilty. >> it was like taking a breath of fresh air. >> reporter: although jon corwin still feels the lasting pain of regret. >> i just wish, wish i could have been there for her more. i tried my hardest, but it wasn't enough. >> erin was a kid. she had her whole life ahead of her. she just didn't know that, in my opinion, she was dealing with the devil. >> chris's wife, nichole, told detectives she had nothing to do with erin's disappearance, and she has not been charged with any crime. >> is there still a chance, is nichole out of the woods? >> not every door has been closed. >> reporter: but for erin's mom, the door on chris lee is closed. and she breathes a little easier knowing it. >> every time there's a hearing, your emotional scab gets ripped off. and to know that i'm not gonna have to deal with that. >> reporter: lore finds comfort here. way out in the joshua tree desert. where doug billings "cave doug" created this. in the desolate place where erin's life was cut short. a garden now grows in her memory. >> reporter: when you look at that desert garden, what are you thinking? >> it's beautiful, like my girl. it's a peaceful place. i have a peace that can't be explained. i decided i couldn't be bitter and angry. he's already taken enough from me. and if i'm bitter and angry, he's taking my mind, my soul, and my heart and i'm not giving him that. ♪ ♪ this sunday, the migrant crisis. >> don't come over. don't leave your town or city or community. >> the u.s. seeing the biggest border surge in two decades. >> why do you think it's picking up? >> i think it's a policy change, honestly. >> republicans blame the biden administration. >> mr. secretary, don't tell me this isn't a , crisis. >> and the administration pushes back. >> aat crisis is when a nation willing to rip a 9-year-old child out of the hands of his or her parent and separate that family to deter people from migration. >> this morning, i'll talk to homeland securit