After three murders of elderly women, the victims being strangled and penetrated with foreign objects, the Boston police conclude that they have a serial killer to catch. As the murders stretch over several police jurisdictions, Massachusetts Attorney General Edward W. Brooke appoints John S. Bottomly as head of a "Strangler Bureau" to coordinate the investigation. Several suspects are interrogated and released. As the body count grows, Bottomly, in desperation, calls in a psychic, Peter Hurkos, who pinpoints Eugene T. O'Rourke, a man who seems to fit the profile. The man is taken in for psychiatric observation for ten days but nothing implicated him to the murders. Another murder is committed while O'Rourke is under observation, clearing him of suspicion. While the 1963 funeral of John F. Kennedy is on television, Albert DeSalvo leaves his wife and children, under the pretext of work. He gains entry into the apartment of a woman, Dianne Cluny, by posing as a plumber sent by the building supervisor. He attacks her, tying her to her bed with rags ripped from her dress. DeSalvo is taken aback by the sight of himself in a mirror as he tries to subdue Dianne and she struggles free and bites his hand; DeSalvo flees. He tries to enter the apartment of another woman, only to find that her husband is home. DeSalvo is apprehended by a passing police patrol. Found incompetent to stand trial for attempted breaking and entering, he is committed to a hospital for psychiatric observation. By chance, Bottomly and Detective Phil DiNatale pass by DeSalvo in an elevator, where they had been visiting Dianne, who survived the earlier attack. Observing the wound on DeSalvo's hand, the pair make him a suspect for the Boston Strangler murders. Conventional interrogation is ineffective because the treating physician thinks that DeSalvo suffers from a split personality: he has two identities that are unaware of each other. His "normal" personality fabricates memories in place of the memories of murder committed by the "strangler" personality. The treating physician thinks that DeSalvo could be made to confront the facts but that the shock risks putting him in a catatonic state. Bottomly expresses the opinion that catatonia would be the second-best thing to a conviction. Under the condition, imposed by DeSalvo's defense counsel, that none of what comes to light is admissible evidence in court, Bottomly is allowed a final round of interviews with DeSalvo. After several sessions, Bottomly manages to reveal DeSalvo's hidden personality to himself. Reeling from the shock, DeSalvo slips into a catatonic state.
According to Fox records the film required $8,625,000 in rentals to break even and by 11 December 1970 had made $11,125,000 so made a profit to the studio.
Critical response
Film critic Roger Ebert gave three stars out of four but criticized the film's content, In the same vein, The New York Times film critic Renata Adler wrote, In 2004, film critic Dennis Schwartz discussed the film's style,
