When a mother of four is found murdered near her home in October 1975, DCS Dennis Hoban leads the investigation. After more murders occur, detectives realize they are dealing with a serial killer. With no serious leads, Hoban is sidelined from the investigation by Chief Constable Ronald Gregory, who seeks to run the investigation his way. After subsequent murders, Gregory appoints Assistant Chief Constable George Oldfield to take over the inquiry.

As the murders continue, Oldfield is galvanized by the arrival of a series of letters and a tape, purportedly from the killer himself. The investigative squad become fatally entrenched in their belief that the killer means to target sex workers. Eventually the team decides to go public with a massive press appeal, hoping to flush out the sender and as a result, the killer.

After a chance arrest, the killer is finally identified and caught. Through the eyes of his many victims - the survivors, the mothers and fathers, and the many children - it is evident that the emotional effects and shockwaves these crimes caused will last through the decades.