Dateline | April 03, 2013
>>> i remember sitting at my mother's house. and she just saying i feel like the gates of hell are opening.
>> it was a there's afternoon, summer 2010 , and a violent summer rainstorm had barreled through the towns ringing the outskirts of philadelphia brig 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.
>> reporter: 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.
>> reporter: 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 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 we grew up on. tell me that and i'll leave you alone.
>> reporter: 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. anything that we could do to get them to go over there.
>> reporter: detective maurer agreed to stop by the apartment and talk to morgan .
>> and she seemed genuine, like she wanted to help me.
>> reporter: 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 had received a message from kevin that he was leaving and she showed me these text message exchanges, something to the effect, are you kidding me? and he said, no, i'm done, i can't do this any more.
>> reporter: the detective also kevin 's young employee howho'd been hanging around the apartment complex with morgan and the kids.
>> he just seemed like a young kid, 21 years old.
>> reporter: 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, he's 21. that's absurd. there's no affair.
>> reporter: absurd is precisely what friends mike and noel 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, she's not right. there's something wrong with her.
>> reporter: 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.
>> reporter: 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 had a troubled relationship, i thought that kevin really was fed up and had had enough of morgan and left.
>> reporter: 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.
>> that's them. that's him.
>> reporter: 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.
>> okay. yeah, they're getting in the truck now.
>> reporter: 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.
>> reporter: he frantically called the police looking for detective maurer.
>> i'm afraid his wife and the new boyfriend are making a move to leave. they're leaving, they're leaving.
>> reporter: only they didn't go far. chris followed them as they drove over to the landscaping business it. turns out the detective was already there. he'd decided to go poke around half expecting to run into kevin back at work.
>> she gets out of the passenger side and walks directly by me. i then walk over to shappell who's still sitting in the passenger seat . he's got a dead stare straight ahead.
>> reporter: there was something inside the truck that the detective thought was peculiar.
>> the backseat was full of clothes. i could see a laundry basket and bags and backpacks. he says, oh, morgan 's going to do laundry across the street. i said, well, morgan 's got a washer and dryer in her apartment, i saw it yesterday. things aren't adding. you. do you mind coming back to the station. i have a couple of questions for you.
>> reporter: as the detective turned his back on steve , something unexpected happened. something chris mengel, still filming, caught on video.
>> here we go.
>> reporter: steve jumped in the driver's seat, pulled out of the lot and sped away.
>> that's him. that's the dude with the red hat .
>> reporter: morgan walks over and sits down on a step, puts her hands on her head and says, oh, my, maybe he did do something to