He's the most prolific serial predator in California history, but remains mostly unknown. His reign of terror began in the 1970s, but the fear lingers today. Who is The Golden State Killer? Investigators past and present are committed to finding out.

Cold case investigator Paul Holes digs deep to understand where the Golden State Killer likely lived and did for work. A chilling phone call is analyzed by the citizen sleuths to see if it adds anything to the growing profile of the perp.

Investigator Paul Holes continues to examine the Golden State Killer's murderous attacks in Santa Barbara. Meanwhile, armed with new theories, the citizen sleuths find a lead good enough to submit to the FBI.