Boston is being terrorized by a series of seemingly random murders of women. Based on a true story, the film follows the investigator's path through several leads before introducing the Strangler as a character. Shot almost exclusively from the point of view of the investigators, the audience is treated to a first hand look at the thrill of a solid lead and the heartbreak of a dead end in the hunt for a killer. Detective Phil DiNatale ultimately gets on the trail of a schizophrenic plumber named Albert De Salvo and cracks one of the most horrifying serial murder cases in U.S. history.