Your teenagers could be planning it right now. Sneaking out of your house, joyrij joyriding around town. But this would be just the start of a mystery that devastated a community. What did this... See More
Your teenagers could be planning it right now. Sneaking out of your house, joyrij joyriding around town. But this would be just the start of a mystery that devastated a community. What did this ominous tweet, #what if I could get away with it, mean? The texts and tweets and Facebook fights between B.F.F.S. Where getting unfriended is just the beginning. Here's Ryan smith. Reporter: They were 16 and inseparable. Best friends, high school sophomores Shelia, Skylar and Rachel. It was always those three together. You barely ever saw one of them by themselves. Reporter: Silly in their selfies. Giggly teenage girls. They're pretty, they're sociable, they're popular. Reporter: But behind their smiles, secrets that would shock everyone they knew. The level of deception, it's mind-boggling. The police were just as shocked as we were. No one was expecting anything like that. Pure evil. Reporter: Nestled in the green mountains of west Virginia, the city of morgantown, home to west Virginia university, known as a friendly family place. What's it like here in morgantown? It's peaceful, it's a small town that's growing really fast. Nice people. Reporter: Dave and Mary neese live in an apartment in the tiny morgantown suburb star city. Dave works at a local Walmart, Mary at a medical office. Their lives wrapped around their only child, Skylar. Hey, gorgeous. Hi, daddy. Reporter: Treasuring every spin, every laugh, and every childhood memory. I think it was the time she had the tea party for me, and after Mary came home, she noted that Skylar couldn't reach the faucet and I'd been drinking toilet water for the whole tea party. That was a good memory. At the time it wasn't a good memory. My crazy girl. Reporter: She was daddy's little girl. I spoiled her beyond rotten. She was very loyal to her friends, the people she thought was her friends. Reporter: When Skylar was eight years old she met another spirited child with whom she developed an instant bond. Her name was Shelia eddy, and they became thick as thieves. If they weren't together, they were on the phone together. And that's literally 24 hours a day. I'm serious. It was always, you saw one of them, you saw the other one. Reporter: What was your relationship like with Shelia? She was like a part of our family, she really was. I mean, just like one of our kids. Reporter: As a teenager, Skylar had a 4.0 gpa, a part-time job at Wendy's, and an active social life. In their freshman year at university high school, Skylar and Shelia meet the striking redhead Rachel Shoaf. The duo becomes a trio. Kelly Kerns was close to Rachel. She called me her cool aunt. She was like a daughter to you. Yes. Reporter: Kelly says Rachel was charismatic, popular, and talented, cast as the lead in the school play. What was she like on stage? She was a natural. Reporter: On Rachel's 15th birthday, Rachel introduced Kelly to her new best friends Shelia and Skylar. Here they are that night. They were two adorable little girls smiling up at me, you know, just looking so angelic. Reporter: But that vision of angels would soon be shattered. July 5th, 2012, Skylar finishes a night shift at Wendy's. Skylar walked through the door, gave her mom a hug, and said, "I love you, mom." Then she hugged me and said, "I love you, dad." She went to bed. Reporter: The next day Dave and Mary go to work. But when he returns home that afternoon, Skylar's bedroom door is still closed. I knocked on her door. There was no answer. So I said, "Sky, come on! You got to get up." And I still didn't get an answer. So I opened the door, and I looked down at her bed and it hadn't been slept in. And it scared me. So, I immediately called Mary. She said, "She's not home?" And I said, "No." Reporter: Concerned, his next call -- Shelia. She answered on her first ring. And I said, "You got any clue where Skylar is?" She said, "No." I said, "When's the last time you talked to her?" She said, "Last night about midnight." Reporter: Looking for clues in Skylar's bedroom, Dave discovers something out of place. When you came in here that day, describe what this looked like. The screen was gone completely, and I found it in her closet. And the window was open about that much so she can get her fingers and lift it back up. I found a bench right here. Reporter: Outside the house Dave points out where he saw a bench, a way for Skylar to climb back into her bedroom. Then I knew. Oh my god, she snuck out last night and she's not home. Now I started freakin'. Reporter: It's now 4:00 P.M. And it's time for Skylar's next shift at Wendy's. Skylar had never missed work, but today she's a no-show. Wendy's called and said, "Hey, is Skylar coming to work today?" And I said, "Aw, Jesus." And Mary said, "Call 911." 911, do you have an emergency? I have a 16-year-old daughter, can't get a hold of her, and I'm scared to death. Has she done this before? No. Reporter: Just then, Mary gets a phone call from Shelia. What did she say? Her words were, "I have to tell you the truth about what happened last night." She proceeded to tell me that her, Skylar, and Rachel had snuck out the night before, and that they had driven around star city. Were getting high, and that the two girls had dropped her off at the end of the road. Because she didn't want to wake us up sneaking back in. I was scared to death. I mean, I didn't know where my baby was. It was horrible. Reporter: Shelia and her mother come over and offer to help search for Skylar. We immediately went looking for her, going door to door. And we just, we couldn't find her. Reporter: But then Mary remembers what will become a major key to finding Skylar's whereabouts. Mary said, "Oh, what about the surveillance?" We got surveillance at our apartment. Reporter: The surveillance camera, intended to capture intruders, instead reveals this grainy image of that night. A car pulls up at 12:30 A.M., 30 minutes after Shelia says she dropped Skylar back near home. Skylar is seen sneaking out of the house she slips into the car and disappears. What were you thinking when you saw her head flash on that screen and she's walking to that vehicle? For a second I felt relief 'cause at least I know she didn't get abducted or anything. And it wasn't like she was pushed in. She willingly got in the car. Reporter: What did police tell you that they thought happened? They thought that Shelia had dropped her off and Skylar came back home, and then snuck out again. Reporter: For officer Jessica Colebank and corporal Ronnie Gaskins, the video is their best and only clue. What were you looking for? Anything. Trying to get pictures of the tires, the rims, but it's just too grainy. It just raised millions of other questions, of who did she go with and where did she go?
This transcript has been automatically generated and may not be 100% accurate.