>> what had happened behind closed doors? >> she laughed and said, "no, there's no affair." >> someone was keeping secrets, and even police couldn't wrap their heads around this one until they found it, a trail of texts. >> we were like, holy smokes, it's right there. >> it sure was. every stunning detail. >> snapple iced tea seemed the perfect tool to put the poison inside. >> was this a loving spouse or a lethal one? police were in for a killer surprise. >> i feel like the gates of hell are opening. >> i don't know what they were thinking. hello. and welcome to "dateline." kevin and morgan mengel had their share of ups and downs, but through it all they seemed to make it work. then one of them disappeared. it would take a family's relentless pursuit of the truth to jump start the investigation, but soon a stunning confrontation in a parking lot would put police on the trail of a killer and reveal a diabolical recipe for murder. here's hoda kotb with "toxic." >> how much do we reveal to the ones we love? do we keep our betrayals hidden behind closed doors or do we hide in plain sight, masking our deeds with words? >> the text message says, "i'm fine, just clearing my head." >> that was kevin mengel for a time, clearing his head he told his family and friends. facebook status, wants to be left alone. >> maybe he just had enough and needed a vacation for himself. >> but there was a trail of electronic messages that seemed to tell another story, a far more sinister one. >> we were floored. it was all there for us to read. you can't make this stuff up. >> which was fact and which was fiction? >> these text messages don't even seem real. like they don't, they just don't seem real. >> long before kevin mengel had a cellphone or a facebook page he was a high school guy in suburban philadelphia with a cute little sister to worry about. >> kevin was the stereotypical older brother. he would follow me around and tell all of his friend they weren't allowed to talk to me and things like that. >> reporter: was he being protective? >> very protective. >> reporter: for as long as michelle can remember, kevin mengel was a family man, a big brother who felt he needed to look after his younger siblings after their parents divorced. >> kevin had a terrible time with it. >> right. >> and just always told us that he would never get a divorce, he would never get a divorce. >> reporter: instead, kevin grew up in search of perfect romance. >> kevin always had girlfriends. >> but he was always sort of a monogamous guy, when he was with one girlfriend he was with a girl. >> yes. and kevin was very committed to making sure that he stayed in a relationship and he gave it his all. >> reporter: kevin was 20 when he met the one, his forever girl, morgan from a few towns away where she graduated from an exclusive catholic girls school. >> morgan was very, very charming. i mean she was very sweet and very attentive to me. always came over to the house just to hang out with me. >> reporter: outgoing and charismatic, morgan made an effort to win over kevin's friend as well, like mike and noelle. >> very nice. very upbeat. very friendly. always smiling. >> reporter: and kevin? well, he fell hard for morgan's charm. >> he just -- he loved her. >> he was head over heels for her. >> reporter: so kevin was about to get what he had always wanted a wife and kids, but just not in that order. morgan gave birth to their first child a few months before they got married. still, theirs was no shotgun wedding. the young couple celebrated in traditional style. >> kevin was on top of the world. >> it was the perfect picture, wasn't it? >> it was the perfect picture. >> reporter: kevin loved being a dad and he and morgan had two more children, but his relationship with his own father was rocky, had been since his parents' divorce. >> we're both stubborn and we're both pigheaded. so didn't call me and i didn't call him and it got into a little bit of a battle. >> years went by? >> years went by. >> by june 2010 kevin and his dad had patched things up, grown closer than ever. they made plans for the whole family to celebrate father's day together. >> he was so excited. he said to me, "dad, i can't wait to come out for father's day," and i said, "i can't wait to have you." i said, "i love you and this is so wonderful." >> he just seemed to be at peace that i had never seen him at. >> then it was the morning of the father's day party when it happened. sister michelle called their mom to check in. >> she didn't sound right. i said, "are you okay?" she said, "kevin left" and she just started crying hysterically. "kevin left, kevin left." i said, "mom, something's not right here." he left the three kids, he left morgan, i don't know where he went, he won't pick up his phone, he just sent me a text message. >> kevin, the till-do-us-part romantic, leave his wife and kids? perhaps morgan put it best when she typed out their father's day regrets to kevin sr. >> we received a text message from morgan saying, due to unforeseen circumstances we will not be able to be there today. happy father's day. >> unforeseen circumstances? what exactly did that mean? >> we all knew how excited he was before father's day. it would be the one day kevin would not miss ever, no matter what happened. >> no matter what happened. where had kevin mengel gone? >> coming up, maybe there was a reason for kevin to hit the road. >> i thought morgan was having another affair. >> when "dateline" continues. and slows sugar absorption to promote healthy blood sugar levels. so you can feel lighter and more energetic metamucil. support your daily digestive health. and try metamucil fiber thins. a great tasting and easy way to start your day. two loads of snot covered laundry. only one will be sanitized. wait, what? adding lysol laundry sanitizer kills 99.9% of bacteria detergent alone, can't. carl is saving big, holiday shopping at amazon. so now, he's free to become... choirmaster carl. ( ♪♪ ) what a pain in the... alice? if it's "let's wrap this up" season, it's walgreens season. when kevin mengel was a no-show for the family barbecue on father's day, his sister michelle was disappointed and more than a little confused. >> he had called my husband to say how excited he was to spend father's day that sunday with all of us. >> so it was supposed to be a big father's day celebration? >> big father's day, and he couldn't have been more excited. >> kevin's younger brother chris also knew how much he was looking forward to being with his family. after all, kevin had just reconciled with their dad after many rocky years. >> i thought, man, this is odd. why would he do this now? it doesn't make any sense. >> the story morgan, the wife, told was that kevin had taken off, told her that the marriage was over. in fact, by father's day he had already been gone for two days. >> kevin's fine, he's clearing his head. >> what do you mean, kevin's fine? >> he just had to leave, he's get away and clear his head. >> he needed space? >> he needed space. >> i can see him saying i just need to get away, so that part of me said okay, he just did that, he's going to come back in today or tomorrow, whatever. >> we just have to be patient and wait? >> we just have to be patient. >> patient, because those close to kevin and morgan had seen the couple's ups and downs before. their breakups, in fact, were almost an annual event. >> it was like clockwork. every august around their anniversary we would expect the phone call that morgan picked up and left, and kevin would call us crying hysterically. he would just be completely distraught. >> he said, "i love her. i can't help it, i love her." >> and soon morgan would return, kevin's world would right itself and they would be as good as newlyweds for a while. >> she could act like nothing ever happened, and acting all lovey-dovey, sitting down on his lap. >> but now what was weird about this separation was that kevin had taken off, not the other way around. >> she always took the kids and she always left. kevin never once walked out on her. >> his family worried this must have been the fight to end all fights, and it wasn't like kevin not to call his family for support. the only person he reached out to was his mom. a few days after he disappeared he sent her a cryptic text message that seemed to alarm her more than put her at ease. and so kevin's mom did something that seemed a little drastic. she called the west goshen police to report him missing. >> we thought maybe she was overreacting to kevin leaving. >> david maurer was a detective on the case. >> there was no reason to believe that anything had happened to kevin. she was receiving text messages from kevin's phone. >> their feelings were that if somebody is communicating with him, then he's not missing. >> kevin's dad agreed. >> i was a little concerned that she may end up with a little bit of egg on her face because he was going to show up and -- >> right, she had called the cops. >> yeah. >> okay. >> and not long after the initial missing person report was filed with the police department, an officer called the family back to say kevin had been spotted not far from his home. >> one of the officers stopped at a check cashing place right up the street from where morgan and kevin live, and the owner of the check cashing place was very familiar with kevin and he saw him across the street, so that leant some credibility that kevin was in the area. >> he was close to home, sending texts to his wife and mother, just refusing to see or speak to his family, and he did finally respond via text to his father. >> what did you get back? >> doing okay, just need time away. >> and kevin's sister received this message. >> he says, i'm fine, worry about morgan, she's the one you should be worried about. >> but morgan it appeared was doing just fine. the couple owned a landscaping business and monday morning morgan showed up to meet the crews and told them she was now in charge. employee al recalls she had the garage looking spotless. >> there's always oil drips on the ground. this day you could have ate off this floor. >> but this was new too as al went about his monday landscaping jobs. he noticed morgan, the boss's wife, flirting with a 21-year-old employee named steve shappell. >> morgan looks at me and says, steve knows what color underwear i have on. and steve's like, yeah, pink with black stripes. right off the bat. >> and when al had a question about an assignment -- >> i would call morgan and steve is there. steve is answering her phone. >> why was this kid who mowed lawns and was barely old enough to buy a beer suddenly acting like the new man in charge? kevin's sister, michelle, remembered him as a quiet, unassuming young guy who had done some work on her yard weeks earlier. >> this kid steve could not have been more polite to us. >> so what would kevin think now of his employee spending the workday at the pool with his wife and kids as michelle observed when she took a drive by? >> i drove by her development and she was sitting out at the pool with steve and the kids. >> okay. you see steve sitting with her and you're thinking what? >> i thought morgan was having another affair. >> it was no secret among those who knew the couple that morgan had strayed before. could kevin have suspected morgan was at it again and was that the final straw that drove him out? no way to know. he still was not taking calls. and then five days after he disappeared kevin finally had something to say to everyone who knew him in the most public way possible. he posted an update on facebook. status, wants to be left alone. >> he wants to be left alone. some of his friends backed off then. you know, his friends also were looking for kevin. after the facebook thing came up they were like, it must be another morgan and kevin fight. >> maybe he had a nervous breakdown or maybe he just had enough and needed a vacation for himself. >> but to kevin's immediate family this facebook update was far from reassuring. to them it was an ominous red flag. >> every other update that kevin had put on there had come from his cell phone because it shows the little cell phone, and this one came from a computer. >> which seems so odd. the family knew kevin did everything on his cell. what's more, the wording in his text messages he'd been sending just didn't sound like kevin. for example, michelle wondered when did he start calling her sis? >> in the pit of my stomach i just felt something bad had happened to kevin. >> and if the cops would not investigate, the family decided it was time to do some detective work themselves. >> i'm afraid his wife and the new boyfriend are making a move right now to leave. they're leaving. coming up -- what would it take to alert the police? >> things just aren't adding up. i said, "would you mind coming back to the police station? i do have a couple more questions for you." >> when "dateline" continues. it's simple. pill, once-daily. #1 prescribed for td. learn how you could pay as little as $0 at ingrezza.com ♪ and i'm gonna keep on lovin' you, ♪ ♪ 'cause it's the only thing i wanna do. ♪ turns out everyone does sound better in the shower. and it turns out the general is a quality insurance company that's been saving people money for nearly 60 years. ♪ 'cause it's the only thing i wanna do ♪ shaq: (singing in background) can't unhear that. for a great low rate, and nearly 60 years of quality coverage - make the right call and go with the general. . it was a thursday afternoon, summer 2010 and a violent summer rain storm had barrelled through the towns ringing the outskirts of philadelphia, bringing down trees and power lines. almost a week had gone by since kevin mengel left his wife and kids. >> people gathered at my mom's house. everybody just sat there waiting. >> kevin's parents and siblings had not spoken with him, heard his voice, that is. the only communication he was making was on facebook and through text messages. >> i think i may have said in there, call me or one of the family members, and he said, "i am speaking to a family member. i'm speaking to my wife and that should be enough for everybody." >> but it was not enough because now a bizarre and horrifying thought had begun to take root and grow. the mengel family suspected that all of those messages were not coming from kevin at all. >> i left another message for him saying, "can you just tell me the name of the street that we grew up on?" just tell me that and i'll leave you alone. >> the police initially didn't even consider kevin a missing person, but now the family begged them to take another look. >> we went back to the police again and pleaded. we tried to think of anything. the kids are home alone, she's not there, you know, anything we could do to get them to go over there. >> detective maurer agreed to stop by the apartment and talk to morgan. >> and she seemed genuine, like she wanted to help me. >> morgan invited the detective in and told him the same story, kevin had walked out on her and the kids and she had proof, text messages in her own phone from kevin breaking it off. >> she'd received a message from kevin that he was leaving and she showed me these text message exchanges. something to the effect of, are you kidding me? and he said, no, i'm done, i can't do this anymore. >> the detective also spoke with steve shappell, kevin's young employee who had been hanging around the apartment complex with morgan and the kids. >> he just seemed like a kid, a young kid. he was 21 years old. >> and morgan scoffed at the idea that they were anything more than friends. >> she laughed and said, no, i'm a married mother of three, i'm 34 and he's 21. that's absurd. there's no affair. >> absurd is precisely what friends mike and noelle would have said had they heard that. they knew firsthand that morgan had a long history of cheating, sometimes even with kevin's closest friends. >> she would tell me how they would have sex in her and kevin's bed when he would go out, how they would have sex in the cars, you know, the business cars. >> i said to myself, you know, she's not right. there's something wrong with her. >> and kevin's family? by now they were sure morgan and the young landscaper were up to something. michelle confronted morgan directly. >> i said, i'm not okay with this, like he just disappeared. like i don't believe you, like i don't. >> adding to their worry, they say morgan had not let them see the three kids since kevin disappeared and they worried she might leave town. they asked the detective if he would do surveillance on the apartment, but he said no. >> i said based on the fact that we had a witness that saw him, the fact that i now know that morgan and kevin have a troubled relationship, i thought that maybe kevin really was just fed up and had enough of morgan and left. >> so the mengel family took the investigation into their own hands. brother chris decided to stake out the apartment overnight. he brought a video camera with him. >> okay. what's that? >> early friday morning he filmed steve shappell coming and going as if he now lived there, taking kevin's place. and what was strange, it looked as though steve was packing up morgan's truck. >> they're coming back. >> okay, yeah. they're getting in the truck. >> to chris it sure looked like morgan and steve were getting ready for something. >> he has a bunch of crap with him. morgan has a bunch of stuff too. >> he frantically called police, looking for detective maurer. >> i'm afraid his wife and the new boyfriend are making a move now to leave. they're leaving. they're leaving. >> only they didn't go far. chris followed them as they drove to the landscaping business. it turns out the detective was already there. he decided to poke around, half expecting to run into kevin back at work. >> she gets out of the passenger's side and walks directly by me. then i walk over to shappell who's still sitting in the passenger's seat and he has a dead stare straight ahead. >> there was something inside the truck that the detective thought was peculiar. >> the back seat was full of clothes. i could see a laundry basket, bags and backpacks. he said, oh, morgan is going to do laundry across the street. i said, well, morgan has a washer and dryer in her apartment. i saw it yesterday. things just aren't adding up. i said, would you mind coming back to the police station, i do have a couple more questions for you. >> and in that moment as the detective turned his back on steve, something unexpected happened, something chris mengel, still filming, caught on video. >> yo, yo, yo. >> steve jumped in the driver's seat, pulled out of the lot and sped away. >> that's him, the dude with the red hat. >> that's steve. >> morgan walks over and sits down on a step, puts her hands in her head and says oh my, maybe he did do something to kevin. >> morgan breaks her silence. what had she been hiding? coming up -- >> steve had said to me that he loved me and would do whatever it took to have me. >> when "dateline" continues. nurse mariyam sabo knows a moment this pure... ...demands a lotion this pure. new gold bond pure moisture lotion. 24-hour hydration. no parabens, dyes, or fragrances. gold bond. champion your skin. hello, here's what's happening. the world health organization has labeled the new onlynicron variant a variant of concern. they need more data, the speed of transmission have the scientific community on high alert. stephen sondhaim has died at the age of 91. in the word of his classic into the woods, sometimes people leave you halfway through the wood. do not let it grieve you. no one leaves for good. now, back to "dateline." >> welcome back to "dateline." kevin mention em's family had not seen him for days, fearing the worst, they reported him missing to police. at first, investigators believed he had is simply left his wife. then there was a very strange incident and their specks were raised. now, this case was about to heat up. once again, here's hoda kotb with "toxic." a kotb with "toxic. kevin mengel's family had not seen him for days, and fearing the worst they reported him missing to police. at first investigators believed he had simply left his wife, but then there was a very strange incident and their suspicions were raised. now this case was about to heat up. once again, here is hoda kotb with "toxic." >> it sounds so hokey but three months before i had a terrible you nightmare that something had happened to kevin and that kevin was hurt, and i woke up crying hysterically in my bed. >> michelle hopkins, kevin mengel's younger sister, was now in a waking nightmare. her brother kevin had been missing for a week, and the young man who appeared to be having an affair with her sister-in-law had just fled from police. >> why did he just steal her pickup truck and flee when i asked him to come back to the police station? >> the situation suddenly looked much worse than detective david maurer had thought. he brought morgan to the station and called his partner and long-time friend, darryn sedlack. >> he said, can you get in here, something is going on. i'm not sure what but shappell just stole morgan's truck and fled and we can't find him. >> we had no idea it was going to turn out the way that it did. >> their first priority was to find steve shappell, who was now on the lam. they tried tracking his cell which was in the truck, but it was turned off. but morgan's phone was in there and it was turned on. she gave detectives permission to track it. >> so we focused all of our efforts on morgan's telephone. >> meanwhile, morgan was downstairs in the interview room as detectives tried to find out what steve was running from. >> do you think maybe steve hurt kevin? >> i don't know, but by his reaction today -- >> he takes your truck without your permission and in my terms flees the scene. >> absolutely. >> although morgan had previously denied the affair with steve, the much-younger landscaper, she was now telling the detectives they were having a relationship, a result, she said, of an unfulfilling marriage. >> it was just a bad marriage. >> okay. tell us. >> a really bad marriage. the yelling, the screaming, the fighting, the "i can't ever do anything right." >> so tell us about your affair. how did steve treat you? >> talked to me like i was a human being with feelings, paid attention to me. >> and she repeated yet again how kevin had walked out on her and the kids one week earlier. >> he was leaving. he wanted a fresh start. >> and did you respond to him? >> i said, are you kidding me? he told me he was not kidding and to tell the children that he loved them. >> now i have to ask, in the truck i saw a bunch of clothes in the back of the truck. who did they belong to? >> steve. he said he was taking his stuff, his clothes that he had accumulated at my house, home. >> he's been staying there? >> a few nights, yes. >> did you ever think that maybe kevin would come home and steve would be there and there would be an issue? >> no, i hadn't thought about that. >> and i said if i get in a fight with my wife, i said, nobody's moving into my house. >> as a husband, as just a sensible person, to me that -- >> it is poor judgment. >> poor judgment and a bad marriage was all kevin's wife would admit to, but the family knew that morgan had a history of deception, a strange one that went back many years. >> there's something that is innocent looking in her face, that you just believed her. whatever she said, you just believed her. >> one of her biggest lies, they say, was back when morgan got pregnant before the couple was married and refused to tell the truth about it. >> we were looking at her saying, you're pregnant. and she said, "i am not pregnant." >> and she would wear two girdles at a time and heavy sweaters. i said to her, morgan, did you tell kevin? she said, no, i just told him that i'm on birth control and it's causing my stomach to swell. >> and when the baby was born, kevin was in shock. >> we got a phone call the next day from my brother kevin hysterically crying, telling me that i'm an aunt. >> was he crying tears of joy? >> i don't think so at that time. i think he was so scared, and it caused the first real fight between my brother and i because i was so very disgusted by morgan. >> so when kevin went missing the family had been convinced from day one that morgan was hiding something, and now the detective was too. after hours in the interrogation room she gave the first hint that she knew more than she was saying about her young boyfriend, steve. >> steve had said to me that he loved me and would do whatever it took to have me, and then last night he said he had an uneasy feeling. he apologized to me and said it was his fault. i asked him what was his fault, and the only response i got was "the entire situation." >> you think steve hurt kevin? >> at this point, yeah, i do. >> morgan asked for a cigarette break. detective maurer went outside with her. she had been talking all this time without a lawyer and the detective wanted to keep the conversation going, hoping she would reveal something, and did she ever. >> we're standing in the shade because it is still extremely hot and there's no air conditioning in the building because of that thunderstorm and she says, steve told me he hit kevin in the back of the head with a shovel. i'm like, whoa. we run back in, i turn the recording back on at that point. >> morgan, you just told me something. would you mind repeating it? >> steve hit kevin in the back of the head with a shovel. >> here was morgan laying the blame on steve, telling police he had attacked and killed kevin at the landscaping garage on the day he supposedly left her and the kids. the detective was stunned. that earlier sighting of kevin alive and well in town, had it been a mistake? how long had she been lying to police? >> i'm floored. i'm like, why didn't you tell me this? when your boyfriend tells you that he hit your husband in the back of the head with a shovel, you call the police. >> are you trying to protect steve? >> not at this point. >> morgan said that steve had only just revealed to her what he had done, but the detective suspected he wasn't getting the full story. hoping to trip her up he asked her to write down a timeline of events for the week kevin disappeared. >> you going to write it down? >> uh-huh. >> most of what she wrote stuck to the story, but this was a strange detail. >> she writes snapple on one of her statements. i said, "what does snapple mean?" >> coming up -- a new revelation. that single word morgan had written involved a deadly surprise. >> who handed the snapple to your husband? >> when "dateline" continues. ♪♪ the first break in the what a pain in the... alice? if it's "let's wrap this up" season, it's walgreens season. 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(kate) black friday better with verizon. because everyone, everyone, everyone deserves better. shop online, in store, or call today. ♪ ♪ cases of anxiety in young adults are rising as experts warn of the effects on well-being caused by the pandemic. ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ( ♪♪ ) what a pain in the... alice? if it's "let's wrap this up" season, it's walgreens season. the first break in the case of missing husband kevin mention el had come out of the blue. morgan, the wife, under questioning by police revealed that her lover, steve, had killed her husband in the landscaping garage. she was saying steve had done the deed a week earlier and only admitted it to her later. she hid his secret out of fear. >> i didn't know if he was going to whack me upside the back of the head with a shovel of if i did and you guys showed up and he flipped out. >> the man you're having a relationship with tells you that he hit your husband, the father of your children, in the back of the head with a shovel and you don't tell me that information. >> a bit of shock. >> i personally feel it's because you had some role in this. >> i didn't. >> but detective maurer did not believe her. he looked over the timeline she had written out, puzzling over that one word, snapple. why did she write that down? the detective took a break. went upstairs to speak with his partner, detective sedlack. >> and it was sort of like a mental slip. i asked him if he minded if i had a shot. i wanted a chance to talk to her myself. >> and so the detectives decided to play good cop, bad cop with morgan. >> i want to hear everything and you better start at the beginning because the game's over. >> and now morgan was about to offer a new piece to the puzzle, a truly shocking one. it had started as a joke, she said, the two lovers imagining kevin out of the picture. >> joking around how, you know, we could take kevin out. yeah, right. >> what would happen, they wondered, if they put something in his favorite drink. >> he put nicotine, straight nicotine in his snapple that he bought. >> following a recipe that he found online, steve cooked up some chewing tobacco into a toxic substance called liquid nicotine. he then slipped the poison into kevin's snapple. >> and then who handed the snapple to your husband? >> it was on the truck. i did. >> did you say anything to your husband like that drink's for you? >> no. the rest of us don't drink it, so. >> and then what? >> i left and got my kids off to school. >> but morgan insisted she never expected any real harm to come to kevin, never expected steve would take it as far as he did. and besides, it wasn't the poison that killed kevin but the blows to the head which steve had done alone inside the landscaping garage. >> i wasn't being serious. apparently it did turn into a serious conversation on his end. and yes, i did hand kevin the snapple bottle with nicotine in it. after that i was not involved in it. >> you guys killed someone and you expect me to believe that you didn't talk about it? >> no. i didn't want to talk about it. i looked at my kids and felt terrible. >> so terrible that you made up text messages to his family members about him calling you, texting you. >> i did not do that. >> who did? >> steve did that. >> it was steve, she said, who used kevin's phone to send messages to his family pretending kevin was still alive. and steve and steve alone who had buried kevin in some woods a few towns over. >> and where did he tell you that he took kevin? >> behind a high school. there was a development being built. >> the interrogation had turned deadly serious, but the detectives thought that morgan's demeanor was odd. when detective maurer asked if he could take pictures for evidence, he says she didn't look like someone facing a potential charge of murder. >> and while i'm taking these pictures she's actually smiling for the camera, which is weird. >> and in the middle of his bad cop interrogation, detective sedlack says it was almost as if she was flirting with him. >> my questioning was not nice by any means and i just couldn't believe that she was smiling and looking up at me. >> is this funny? >> no. am i laughing? >> you just smiled. >> no, i didn't. >> the detectives felt they had enough. they issued a warrant for steve shappell, who was still on the lam. and morgan? >> we handcuffed her inside of the interview room and told her that she was under arrest for the murder of kevin mengel jr. >> they sent a police officer to talk to kevin's father. >> he said that we believe that your son has been murdered. it was not easy to sit and listen to. >> kevin's three children were spending the day at his sister michelle's house when she learned that kevin was not coming back. >> kevin's kids came in and they just came up and they just started hugging me. and they're like, "what's wrong?" i think they knew. >> michelle had known all along, she says, in her gut that kevin was dead. but how it happened? michelle could not believe what police were telling them. she remembered steve shappell as that scrawny, unassuming guy who worked for kevin mowing lawns. in fact he had done some work on michelle's yard just a few weeks earlier. michelle felt badly when he told her he just had his wisdom teeth out. >> i was so worried about him for the two days that he was there, and to think what he did to my brother. >> and her sister-in-law? it felt impossible to take that in. >> when i saw her mug shot i didn't even recognize her. she just had a different look about her. she's been in my life for 15 years and i didn't even know who she was. >> the next morning detectives recovered kevin's body buried in a shallow grave behind that high school right where morgan said it would be. and the following day steve shappell was picked up nearly 2,000 miles away in colorado. >> i still can't imagine him doing it. i can imagine morgan doing it. i don't know what they were thinking. >> figuring out what they were thinking was now the job of the county prosecutor, and it would prove to be more complicated than expected. >> did she say you need to go dig a hole? >> morgan had pointed the finger at steve, but now he was back and about to tell a very different version of events. >> on the day of the murder she's texting him, has the poison worked yet? and when it's not working fast enough she says couldn't you just pick up a shovel? >> the truth? well, that takes us right back to where our story began. the tale of the texts has another chapter to come. >> coming up -- who was the mastermind, morgan or steve? when "dateline" continues. if you're on medicare and you want to explore your options, the deadline to enroll is december 7th. so, you should act now. where do i find the right medicare plan? at healthmarkets, they search many of the nation's most recognized carriers so they can help you find the right plan, at the right price that's the right fit for you. how long does it take? you could find a medicare plan in just minutes. my current plan only covers 80% of my costs. well, healthmarkets may find plans that cover the rest ... let you keep your doctor with benefits like zero dollar copays, zero dollar deductibles and zero dollar monthly premiums. they'll even search plans with prescription drug coverage, vision, dental and hearing aids. you may even qualify for free gym memberships! so call or visit healthmarkets today to see if your current plan is the right fit for you or, you may find a plan that can help save you money. healthmarkets sounds great! how much does it cost? 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( ♪♪ ) what a pain in the... alice? if it's "let's wrap this up" season, it's walgreens season. where's mom? she said she would be home in time for the show. if it's "ldon't worry sweetie, shen, promised she'd be here for it. oh! nice shot! thanks! glad we have xfinity. with wifi speeds faster than a gig. me too. [claps] woah! look! [chuckles] mom is on tv! she's amazing! [screams and laughter] yeah! xfinity brought us together after all. get started with xfinity internet and ask about wifi speed fast than a gig. click, call or visit a store today. morgan mengel and her young lover steve chappelle were both sitting in jail for the murder of morgan's husband kevin. morgan had confessed to playing a small part in the crime, helping steve chappelle come up with the plan to spike her husband's snapple iced tea with poison, only it was a joke, she said, that was taken too far. >> what were your first impressions of her? >> very good. i mean, the allegation compared to the person i was speaking to did not seem to fit. >> morgan's attorney said the case against morgan was weak. she wasn't at the crime scene when kevin was killed and had no convincing motive for wanting her husband dead. >> in fact, financially she was way worse off without him alive. he was the lifeblood. >> you think she had some musings like i wish my husband wasn't around, i wish someone would take care of it. >> i think morgan was walking around with dynamite saying these musings to every people, and steve chappelle was the match that lit that dynamite and it exploded. he is the cold-blooded killer. >> a cold-blooded killer? he hardly looked like one when police picked him up in denver and got him in the interrogation room. he was make, quiet, voice shaking with fear. >> he admitted the crime and thought this was the way to get morgan forever. >> steve said he was not kidding when he came up with the plan. after the murder, far from being scared, morgan was grateful. >> kissed him. she came back with water and began rinsing off. >> which is why the garage looked so clean when employees arrived for work that monday morning after kevin's so-called departure. >> she walks in the graham steps over her dead husband, kisses chappelle, and says, let's get a tarp and get to work cleaning the scene. >> so now morgan and steve were pointing fingers at each other about who committed the murder. the d.a. believed steve. he offered steve a lesser charge and offered morgan a mandatory life sentence. >> she used him as a pawn and pulled the strings. >> morgan had a way with men, she just did. she had a way with men. and i think the same way that she had my brother under her spell, she had this kid as well. >> and the d.a. says it was morgan herself who had been sending those fake text messages to kevin's family after the murder, not steve. cellphone tracking records proved it. >> she's texting kevin's family, assuring them that he's okay, he just wants to be left alone. she's the most evil woman i've dealt with. >> morgan mengel went on trial in late january 2012, a year and a half after kevin mengel had been murdered. but in addition to steve chappelle waiting in the wings to testify, the d.a. had something else, something extremely rare in a murder trial. a play-by-play of the crime, courtesy of text messages between morgan and steve as it happened. >> we were like, holy smokes, there it is. it's right there. >> the detectives hat discovered the trove of information when they pulled phone records looking for steve. >> we knew the exact time of death, we knew how it happened, and so we were floored. >> the texts are chilling. four hours before the murder, morgan texts steve. we ready, she types? steve responds, yep, at the shop now. then a half hour before the murder, morgan asks steve about the poisoned snapple. he drinkin' it, she asks? yeah. kind a. i'm waiting for him to bend over. i have a shovlg in my hand, ha-ha. morgan replies, nice, babe. steve doesn't respond. she gives him the final taunt. you backing out? he texts back, it's done, get here. >> as incriminating as the messages sounded, morgan was ready to press her case in court claiming she was no murderous mastermind. >> i'm not so sure she had a fully formed belief that steve chappelle was actually going to do this. >> but the defense never got a chance. a few days into the trial a police officer said something on the stand, hearsay that could prejudice the jury, and the judge sent everyone hope. >> chester county judge declares a mistrial in a love triangle murder case. >> for kevin's family, the delay was torture, more waiting for answers to questions they never wanted to ask. >> i wanted to know if he knew it was happening. i wanted to know if he begged. >> why did you want to know? >> kevin was so sweet and kind, and i know he must have been so, so scared. >> the story of those final moments could only be told by steve chappelle, but even from jail as they awaited their fates, morgan was trying to keep him quiet. she wrote him a letter saying she had given birth to his twins. >> so her game plan was if he thinks we have kids together, he's not going to rat me out. >> yes. and she would ask, i need you to do this so i can raise our children. >> of course, it was another lie, another manipulation. the prosecution and defense were back at the chester county courthouse for morgan mengel's retrial. steve was set to testify, but then another surprise. the day the testimony was set to begin, morgan stopped the trial from happening and changed her plea. she admitted to first-degree premeditated murder. even her own attorney was stunned. >> i believe morgan saw the handwriting on the wall. she realizes that whatever actions she took results in his death and resulted in chappelle killing him. >> steve was sentenced to 40 to 80 years, and morgan, life without parole. for the mengel family who were raising kevin and morgan's children, there was finally justice, they said, in knowing morgan will remain behind bars forever. >> i want her to be in jail for the rest of her life. i want her to know that i'm going to be there when her daughter walks down the aisle. i'm going to be there when her daughter has a baby. i'm going to be there with her sons when they meet their wives and graduate from high school. i'm going to get to see all of that, and she's not. she's in hell, and she's going to live this way for the rest of her life. >> that's all for this edition of "dateline." i'm craig melvin. thank you for watching. oomz