>> you thought of them as a team. >> the three of them became inseparable. >> one ended up missing. >> nobody's heard from her. nobody knows where she is. >> something's wroong. something's bad wrong. >> where cass skylar? someone was hiding something. >> it was the fbi. they were serious. >> twitter, instagram, facebook. you just see things. ridiculously out of control. >> mean girls, were they mean enough to kill? >> she was like, well, she'll blackmail me. >> it was such a shocking and scandalous kind of case. >> it was diabolical. >> evil comes in all shapes and sizes. >> in the gentle rolling hills of northern west virginia, in a sweet college town in the heart of coal country lived three teenage girls. their photos capture a moment in time. they were smart, talented, lovely.