Plot summary

Racing driver Alan Colby [Ronald Lewis] and his new wife Denise [Diane Cilento] are involved in a car crash with a truck. The driver of the truck is killed. Denise is mostly unharmed. Alan suffers head injuries but recovers sufficiently for his doctors to consent to him going on honeymoon to the south of France. Alan struggles to drive a car again and during an embrace with Denise by the roadside he briefly puts his hand around her throat.At their hotel, Alan has a moment of anger when he discovers their room has two beds but quickly relaxes and takes a cable car down to the sea front. Back at the hotel they meet local psychiatrist David Prade [Claude Dauphin] who takes an interest in Alan and invites them to his house.That evening Alan suggests he and Denise go to Prade's for dinner. As they embrace, Alan notices bruises on Denise's neck. One of the other guests having dinner at Prade's is Alan's old friend Harry Stonehouse [Bernard Braden]. During dinner, Prade's analogies of spiders and violent men angers Alan and he strikes Prade before driving off. After the other guests leave Prade offers his help to Denise, explaining Alan is still suffering from concussion and anxiety and needs psychiatric treatment. Prade convinces Denise to help him to help Alan through her fear of Alan's violence and the bruises she has already received.After driving around erratically at high speed, Alan goes to Harry's hotel room and expresses his fear of being violent towards Denise. Harry's advice is that Alan has managed to drive in the dark, thereby overcoming his fear of driving, so he can also overcome his fear of violence.Alan returns to the hotel the next day. Denise tries to convince Alan to visit Prade but Alan resists and becomes argumentative. They decide to end their holiday and return to London. Prade telephones and on hearing their plans, decides to follow them to England.Back at their London home Alan discovers Denise has details of Prade's London practise and they argue again. Alan appears suspicious of Denise's relationship with Prade. Alan imagines strangling Denise then returns to his senses and flees. Denise visits Prade at his London home and he convinces Denise to try and persuade Alan to see him. When Alan returns home he wants to leave her, but Denise convinces him to go to Prade despite his scepticism and mistrust of psychiatrists.During his appointment with Prade, Alan expresses his concern and fears he may kill Denise. Prade notices his anxiety and tension. Alan changed following the car crash but is unable to remember the details of the accident. Prade explains he will help him remember, gives him some medication and instructs him to write down any dreams he may have.At their next appointment, Prade forces Alan to imagine in detail how he would kill Denise and the implications of those actions. At the following appointments, Prade sedates Alan and questions him to try and reveal what happened during the drive in which Alan and Denise crashed. Alan remembers details about the drive preceding the crash, such as Denise was wearing a gold crucifix and he was driving at speed, but does not remember the crash itself.Alan's mental state improves and he returns to Grand Prix racing. Before he leaves to go abroad again, Prade persuades Alan to try one last treatment: recount the drive while breathing carbon dioxide, hoping the distress of not being able to breathe will trigger the memories to return. The treatment causes Alan to remember he was looking at Denise's crucifix around her neck and was on the wrong side of the road. He realises he caused the crash and wants to confess to the death of the truck driver, but then realises Denise must have protected him at the inquest. Prade explains his subsequent reactions about strangling Denise are the result of his subconscious guilt for being responsible for the truck driver's death. Prade feels Alan's treatment is now complete.At home the next morning, Alan wakes to find Denise has gone. Prade arrives and at first they think there must be an innocent explanation, but when Prade realises Alan has not taken his medication and is unable to remember the previous evening, he searches the flat and there are signs he may have killed Denise as Alan described in his earlier consultation with Prade. When Prade finds a case of blood stained surgical instruments Alan panics and blames Prade for misdiagnosis but Prade offers to help him with more treatment, explaining he may receive a shorter prison sentence if he was proven insane at the time of the murder. They leave in Prade's car but Alan panics again and knocks Prade out causing the car to crash into a taxi. Alan provides a false name and address to the taxi driver and leaves for the airport.Back in the south of France, Alan hides in Harry's hotel room, confessing what has happened. By chance he spies Denise boarding a boat and sailing off with Prade. Denise is staying with Prade and his mother but Prade has her there under false pretences. Prade is pretending that Alan is being treated in London by some of his colleagues because he is secretly in love with Denise. Alan suddenly arrives at Prade's house and confronts him with a gun. He suspects Prade and Denise of having an affair but Prade tries to convince Alan the supposed murder was all in his imagination and Denise is there for her own well-being. When Denise supports Prade's explanation, Alan breaks down, uncertain as to what is the truth. However, Denise then realises Prade was lying about Alan being treated in London and other inconsistencies he has told her. Prade is accused of setting up the whole murder scene. Chased by Alan and Denise, Prade flees to the cable car, but it is under repair and crashes to the ground as he tries to escape.