The show begins Monday, Aug. 10, on Freeform and streams the next day on Hulu.
Security footage shows Steven Koecher's last known location in Nevada.
Lashaya Stine's family is still searching for answers 10 years later.
Nearly three decades later, Sabrina's parents remain hopeful she will come home.
The series takes viewers across the country in search of tips that could break these unsolved cases wide open, featuring exclusive interviews with law enforcement and families searching for answers.
