In 1981, 17-year-old high school student, Mary London, was last seen alive getting off a city bus in downtown Sacramento, California. The following day her lifeless body was discovered off a remote road. Initially, the Sacramento police received countless tips and leads about who might be Mary’s killer. But when the leads dried up, so did the investigation. For the next four decades, Mary London’s case remained cold until the use of forensic genetic genealogy gave the police new hope of tracking down her killer.