Still a Mystery

Thirteen-year-old Abby Williams and 14-year-old Libby German disappear while hiking on a popular trail; 13-year-old Dylan Redwine vanishes over Thanksgiving break while visiting his father in Vallecito, Colo.

Florida insurance agent Carla Stefaniak vanishes in Costa Rica; 19-year-old college student Pravin Varughese disappears after a party in 2014.

After a night out with friends, Jaleayah Davis, 20, is found dead; Kelsie Schelling, 21, drives two hours to show her boyfriend a sonogram of their baby, but never makes it home.

In Mobile, Ala., young mother Danniella Vian, 25, disappears into thin air; 19-year-old Holly Moore's suspicious death still raises questions four years after her body is found hanging in her closet