A MOTHER'S CRUSADE, AIRING ON '20/20,' FRIDAY, MAY 13, 10 P.M. EDT ON ABC

What happened to Kelsie Schelling? Twenty-one year old Kelsie mysteriously vanished into thin air in Pueblo, Colorado, over three years ago. The family says surveillance video, text messages and other evidence point to her boyfriend's involvement, yet, to their outrage, police have not yet classified the case as a homicide and have not charged him with a crime. But then a series of Facebook messages to Kelsie's mother raise new theories - is the missing girl's disappearance prompting someone to attempt extortion? "20/20" investigates and confronts those behind the mysterious plot and uncovers developments about what really happened to Kelsie. Ryan Smith's reports airs on "20/20" on FRIDAY, MAY 13 (10:00-11:00 p.m. EDT), on the ABC Television Network.

"20/20" is anchored by Elizabeth Vargas and David Muir. David Sloan is senior executive producer.