Curtis was nominated for a Golden Globe Award for his performance. The cast also featured George Kennedy and the film debut of Sally Kellerman.
After three murders of elderly women, with all victims being strangled and penetrated with foreign objects, the Boston police conclude that they have a serial killer on their hands. As the murders stretch over several police jurisdictions, a "Strangler Bureau" is set up to coordinate the investigations, with John S. Bottomly (Henry Fonda) appointed as its head. Several suspects are interrogated, all cleared of the murders.
As the body count grows, Bottomly, in desperation, calls in a psychic, Peter Hurkos (George Voskovec), who pinpoints a man who seems to fit the profile. The (severely masochistic) man is taken in for psychiatric observation for ten days, but nothing conclusive tying him to the murders is found. There is another murder during the time the man is under observation, thus clearing him of suspicion.
While the 1963 funeral of John F. Kennedy is on television, Albert DeSalvo (Tony Curtis) leaves his wife and children, under the pretext of work. Instead, he gains entry into the apartment of a woman by posing as a plumber sent by the building supervisor. He attacks her, tying her to her bed with rags ripped from her dress. However, when DeSalvo is taken aback by the sight of himself in a mirror as he tries to subdue the woman, she struggles free and bites his hand. DeSalvo then flees.
Later, 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 (George Kennedy) pass by in an elevator, where they had been visiting the woman who survived the earlier attack. Observing the wound on DeSalvo's hand (the woman who survived attack could remember biting him but not his appearance), the pair soon finds him a prime suspect for the Boston Strangler murders.
Conventional interrogation is ineffective because the treating physician theorizes 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 theorizes 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 it 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 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.Tony Curtis as Albert DeSalvo
Henry Fonda as John S. Bottomly
George Kennedy as Det. Phil DiNatale
Mike Kellin as Julian Soshnick
Hurd Hatfield as Terence Huntley
Murray Hamilton as Sgt. Frank McAfee
Jeff Corey as John Asgeirsson
Sally Kellerman as Dianne Cluny
William Marshall as Atty. Gen. Edward W. Brooke
George Voskovec as Peter Hurkos
George Furth as Lyonel Brumley
Leora Dana as Mary Bottomly
Austin Willis as Dr. Nagy
Carolyn Conwell as Irmgard DeSalvo
Jeanne Cooper as Cloe
Richard X. Slattery as Det. Cap. Ed Willis
William Hickey as Eugene T. O'Rourke
James Brolin as Det. Sgt. Phil Lisi
Alex Dreier as News Commentator
John Cameron Swayze as T.V. Narrator
Carole Shelley as Dana Banks
Tom Aldredge as Harold Lacey
Alex Rocco as Detective at Apartment of Victim #10
Film critic Roger Ebert gave three stars out of four but criticized the film's content: "The Boston Strangler requires a judgment not only on the quality of the film (very good), but also on its moral and ethical implications.... The events described in Frank's book have been altered considerably in the film. This is essentially a work of fiction 'based' on the real events. And based on them in such a way to entertain us, which it does, but for the wrong reasons, I believe. This film, which was made so well, should not have been made at all."
In the same vein, The New York Times film critic Renata Adler wrote, "The Boston Strangler represents an incredible collapse of taste, judgment, decency, prose, insight, journalism and movie technique, and yet—through certain prurient options that it does not take—it is not quite the popular exploitation film that one might think. It is as though someone had gone out to do a serious piece of reporting and come up with 4,000 clippings from a sensationalist tabloid. It has no depth, no timing, no facts of any interest and yet, without any hesitation, it uses the name and pretends to report the story of a living man, who was neither convicted nor indicted for the crimes it ascribes to him. Tony Curtis 'stars'—the program credits word—as what the movie takes to be the Boston strangler."
More recently, film critic Dennis Schwartz discussed the film's style: "What mostly filled the split-screen was the many interrogation scenes, where on one side was the suspect and interrogator in the present and on the other side the suspect and his interrogator in flashbacks. Fleischer eschews the graphic violence in the murders and aims instead to try to understand the killer through the script's bogus psychology. The big things the film tried didn't pan out as that interesting, as the flashy camera work counteracts the conventional storyline chronicling the rise, manhunt, fall, and prosecution of De Salvo."
The film was humorously alluded to in the season five episode of All In The Family, "Prisoner In The House."Golden Globe Award: Best Motion Picture Actor - Drama, Tony Curtis; 1969.
Edgar Award: Edgar Allan Poe Award, Best Motion Picture, Edward Anhalt; 1969.
American Cinema Editors: Eddie, Best Edited Feature Film, Marion Rothman; 1969.