When Tanya Van Cuylenborg and Jay Cook were murdered during a trip to Seattle in the 1980s, detectives had few leads. They assumed Tanya and Jay were victims of a serial killer - but without any leads, the case seemed doomed. In deep-freeze, long-term storage, biological evidence from the crime sat waiting. Meanwhile, CeCe Moore began her fascination with genetic genealogy, discovering how it could be used to solve crimes. When Detective Jim Scharf decided to test the cold case's decades-old DNA, he hoped he would bring closure to families. He didn't know that he and Moore would make history.