Andrew Wyke (Olivier), a successful writer of crime fiction, who lives in a large country manor house filled with elaborate games and automata, invites his wife's lover Milo Tindle (Caine), a hairdresser of Italian heritage, to his home to discuss the situation. Andrew explains that he has tired of his wife and wants Milo to take her off his hands. In order to provide Milo with enough money to take care of her, Andrew suggests that Milo steal some jewellery from the house, with Andrew recouping his losses through an insurance claim. Milo agrees and allows Andrew to lead him through an elaborate charade to fake the robbery. At the conclusion, Andrew pulls a pistol and reveals that the entire plot was meant to frame Milo as a robber, giving Andrew an excuse for shooting him. Andrew then appears to execute Milo by shooting him in the head.
A few days later, a policeman, Inspector Doppler, arrives at the manor house to investigate Milo's disappearance. Andrew at first purports to know nothing, but his guilt becomes evident as the inspector collates clues. Frightened, Andrew breaks down and explains the burglary ruse but insists that he only pretended to shoot Milo using a blank cartridge and that his rival left the house humiliated, but alive. Andrew insists that he has no knowledge of what happened to Milo after he left the house. After finding more seemingly unmistakable evidence that a murder has taken place recently in the house, Doppler arrests Andrew for murder. As Andrew is about to be taken to the station, Doppler reveals himself to actually be Milo, in disguise, having engaged in the deception to get revenge on Andrew.
Just as the score seems to be even between the two, Milo explains that they will now play another game, this time involving a real murder. Milo describes how he visited Andrew's mistress, Tea, that afternoon, and strangled her. The police will soon be arriving and that he has planted evidence throughout the house that could well incriminate Andrew in Tea's murder. Andrew dismisses this but rings Tea anyway, to be told by Tea's tearful flatmate, Joyce, that Tea has been strangled and her body found. Andrew now hunts through the house in an increasing fervour, searching for each piece of evidence on Milo's cryptic clues who is revelling in Andrew's predicament. Andrew finds the last item just as Milo sees the police arriving outside the house. Milo answers the door to the police while a dishevelled Andrew straightens himself up. In the background we hear Milo talking to the police officers in an attempt to stall their entry into the house, which Andrew pleaded with him to do. Milo then invites the officers in. However, there are no policemen and Milo reveals that he faked Tea's death with Joyce and Tea's willing help, thus fooling Andrew a second time.
Milo gets ready to leave, but before going he continues to taunt Andrew with humiliating information he obtained from both Andrew's wife and his mistress. Andrew trains a gun on Milo and threatens to kill him. However, Milo warns him that he has anticipated this reaction and really has called the police who are due any time. If Andrew kills him then he will be caught red-handed. Andrew, pushed too far, refuses to believe any of it and shoots Milo, mortally wounding him. The police arrive and approach the house and a distraught and defeated Andrew locks himself in the house. As Milo dies, he tells Andrew to be sure to tell the police that it was "all just a bloody game".Laurence Olivier as Andrew Wyke
Michael Caine as Milo Tindle
Alec Cawthorne as Inspector Doppler
John Matthews as Detective Sergeant Tarrant
Eve Channing as Marguerite Wyke
Teddy Martin as Police Constable Higgs
Shaffer was initially reluctant to sell the film rights to the play, fearful it would undercut the success of the stage version. When he finally did relent, he hoped the film would retain the services of Anthony Quayle, who had essayed the role of Wyke in London and on Broadway. Alan Bates was Shaffer’s pick for the part of Milo Tindle. In the end, director Mankiewicz opted for Olivier and Caine.
When they met, Caine asked Olivier how he should address him. Olivier told him that it should be as "Lord Olivier", and added that now that that was settled he could call him "Larry". According to Shaffer, Olivier stated that when filming began he looked upon Caine as an assistant, but that by the end of filming he regarded him as a full partner.
The likeness of actress Joanne Woodward was used for the painting of Marguerite Wyke.
The production team intended to reveal as little about the movie as possible so as to make the conclusion a complete surprise to the audience. For this reason there is a false cast list at the beginning of the film which lists fictional people playing roles that do not exist. They are Alec Cawthorne as Inspector Doppler, John Matthews as Detective Sergeant Tarrant, Eve Channing (named after the characters Eve Harrington and Margo Channing from Mankiewicz's previous film All About Eve) as Marguerite Wyke, and, Teddy Martin as Police Constable Higgs.
Much of the story revolves around the theme of crime fiction, as written by Dorothy L. Sayers (Lord Merridew = Lord Peter Wimsey) or Agatha Christie, whose photo is included on Wyke's wall, and how it relates to real-life criminal investigations. Class conflict is also raised between Wyke, the long-established English country gentleman, compared to Tindle, the son of an immigrant from the working-class streets of London.
The film received extremely positive reviews, and with modern audiences has 96% positive reviews on Rotten Tomatoes.
The film was nominated for Academy Awards for Best Actor in a Leading Role (Michael Caine and Laurence Olivier), Best Director and Best Music, Original Dramatic Score. Olivier won the New York Film Critics award for Best Actor as a compromise selection after the voters became deadlocked in a choice between Marlon Brando and Al Pacino in The Godfather after Stacy Keach in Fat City won a plurality in initial voting and rules were changed requiring a majority. Shaffer received an Edgar Award for his screenplay.
The film was the second to have its entire cast (Caine and Olivier) nominated for Academy Awards after Who's Afraid of Virginia Woolf? in 1966 and the first where all of the actors in the film were nominated. (Virginia Woolf featured uncredited bit parts by actors playing the roadhouse manager and waitress.) This feat has been repeated only by Give 'em Hell, Harry! (1975), in which James Whitmore is the sole credited actor.
Critics Roger Ebert, Janet Maslin, Gary Arnold of the Washington Post, and several film historians have all noted similarities between Sleuth and Caine's 1982 film Deathtrap. SCTV episode 121 featured Dave Thomas playing Michael Caine, arguing that the two films were different because the library appeared on different sides of the set.
While questioning Wyke, Doppler points out that the clown costume that Tindle was wearing when he was shot is missing, though the clown's mask is later found and put on the head of the plastic skeleton in the cellar. He is probably implying that Tindle was buried with it.
In the trailer for the film, there are the scenes with Doppler laying out the evidence against Wyke as shown in the movie. They include him pulling open the shower curtains in one of the bathrooms and exposing the clown's jacket, dripping wet and apparently with bloodstains on it. This scene was not included in the final film.
The Academy Film Archive preserved Sleuth in 2012.
In September 2006 Kenneth Branagh announced at the Venice Film Festival his new film of the play, with the screenplay by Nobel laureate Harold Pinter. Caine starred in this adaptation, this time in the role of Wyke, while Jude Law played Tindle as a struggling actor. Production was completed in March 2007, and released in the UK on 23 November 2007. The remake did not use any of the dialogue in Shaffer's original script, and was considered unsuccessful in comparison to the original.