When her 19-year-old daughter went missing in 2003, Lori McLeod believed her boyfriend, Scott Kimball, who told her he worked for the FBI, could help find her daughter. Three years later, what began as a check fraud investigation led officials to a shocking conclusion: the very man McLeod trusted to find her daughter was actually her killer. In a new “20/20,” ABC News correspondent John Quiñones unpacks Kimball’s secret life of horrific crimes, exploring his elaborate web of deception and the evidence linking Kimball to multiple murders, some of them committed while he was an FBI informant.