evidence was missing -- heather's body. chris told detectives he dumped her at a gas station. police went there, found nothing and checked security cameras. >> they've got videos from the last 15 days. they have looked at everything from 10:00 a.m. till 4:00 a.m., and your car never even pulls on the lot. >> reporter: chris then changed his story and said he paid someone to get rid of the body. >> i jokingly asked, "hey, you want to make a couple hundred bucks?" >> uh-huh. nope, nope. stop, stop, stop, chris. stop, this isn't working. that's crazier than first one. >> reporter: four hours into the interview, wallace sensed chris was out of stories and out of options. so the detective gave him one last chance. >> i said, "let's cut it out, chris. your time is running out. you need to tell us where she is, and you need to tell us now." >> reporter: the room went quiet, and chris motioned for a pen and paper. then he drew a map.