When Glenda Esmond, the American wife of a distinguished psychiatrist, returns home from a holiday in Paris, she is surprised to find her living room occupied by a young man, Frank Clements, who she has never seen before. She is disturbed to learn that this new addition to the household is a criminal who her husband, a judo expert, had overpowered when Clements held him up at gunpoint one night in London. Rather than have him sent to prison, Dr Esmond has arranged for Clements to stay in his house as a psychiatric guinea-pig; he wants to uncover the motivation for his criminality and cure him through analysis. Glenda is suspicious, particularly as Clements seems more resentful than grateful. Unbeknown to the Esmonds, Clements is taking out his anger on the maid, Sally, who is afraid of him and has given in her notice in protest at his presence.
As the weeks pass, Clements' psychiatric sessions with Dr Esmond are punctuated by riding lessons with Glenda, who begins to become attracted to Clements. One night, Clements slips out of the house and, with an old criminal accomplice, steals some jewellery. When questioned at the house by Police Inspector Simmons, Clements denies all knowledge of the crime. Later, when Esmond is unable to take out his wife because of pressure of work, Clements offers to escort her and they visit one of his favourite haunts, a Soho nightclub called the Metro, whose atmosphere of sleazy sensuality both discomforts and intrigues Glenda. The next morning she witnesses an act of brutality by Clements towards the maid but her desire to upbraid him turns suddenly into a passionate embrace.
The affair between them deepens, even when they are caught on one occasion in a compromising situation by Glenda's husband. Glenda's emotions begin to overwhelm her and, on another visit to the Metro, she loses control, which leads to an argument with her lover. She drives home so wildly that they are pursued by a police car. After she has eluded her pursuers, she sobs uncontrollably.
One morning, Dr Esmond is visited by Sally's fiancé, complaining about Clements and threatening to go to the police. Esmond appears to dissuade the man from this by convincing him of the validity of his psychiatric experiment, but when Clements discovers later that he has simply bought the man's silence for £100, he retaliates by committing another robbery. To Clements' amazement, however, when the police arrive at the house, Esmond lies on his behalf, giving him a false alibi. This in turn triggers the confession that the psychiatrist has been working towards. Clements' criminality stemmed from a deep-rooted hatred of his disciplinarian father, who had turned him in to the authorities when the young Clements had stolen, and then beaten him when the son had sought revenge after leaving prison. After the father died a week later, the stepmother had blamed Clements for the death, initiating a pattern of hate, guilt and fear that had dogged Clements' adult life and led him into a life of crime.
This revelation has a liberating effect, and brings doctor and patient together in a bond that seems more like father and son, but it generates fierce jealousy in Glenda, who fears that Clements has now transferred his deeper feelings to her husband. She implores Clements to run away with her, but now the experiment has finished, Clements wants to atone for his crimes and give himself up to the police. When he leaves the house, Glenda becomes hysterical, pretending to her husband that Clements has attacked her. Taking a gun, the doctor in his turn 'pretends' to have punished Clements by shooting him, a psychological strategy that disastrously backfires when Glenda reveals her love for Clements. Hotly pursued by the doctor and his research assistant, she drives after Clements in her car. Picking him up, she starts talking in a deranged way, and, in her distraught state, loses control of the car, swerving to avoid a passing truck and crashing through an advertising hoarding. Clements emerges safely, but Glenda is killed.
