Twisted Nerve is a 1968 British psychological thriller film directed by Roy Boulting and starring Hywel Bennett, Hayley Mills, Billie Whitelaw and Frank Finlay. The film follows a disturbed young man, Martin, who pretends, under the name of Georgie, to be intellectually impaired in order to be near Susan—a girl with whom he has become infatuated. Martin kills those who get in his way.
Plot
Martin plays catch with his older brother Pete, who has severe learning difficulties and has been sent to live in a special boarding school in London, by their mother. Martin is the only remaining figure in Pete's family life; their father died years ago and their mother has a new life with her new husband, a wealthy banker. Martin expresses concern for his brother's well-being to the school's physician, who is comfortable with Pete's situation, though he makes it clear that Pete cannot be expected to live much longer.
After the title sequence, Martin is shown in a toy store, gazing at Susan, who purchases a toy. As she leaves, Martin follows after having pocketed a toy duck. Two store detectives ask them to return to the manager's office. The detectives assert that Martin and Susan were working together to allow Martin to steal a toy. Susan assures them she has never met Martin.
When questioned by the manager, Martin presents himself as mentally challenged, and calls himself "Georgie". Apparently now disbelieving in a link between them, the manager asks Susan for her address, and Martin appears to make a mental note when she offers it. Sympathetic to him, Susan pays for the toy. Implying that this was a misunderstanding, the manager lets them leave.
Martin returns home and finds his parents arguing in the parlor, over his lack of interest in life. Despite the apparent course of events in the toy shop, they have come to hear of the duck. There is allusion to some perverse behaviour he has exhibited, though this is not elaborated upon. In his room, now behaving as "Georgie", he rocks in a rocking chair while smiling meekly in the mirror and caressing a stuffed animal. The camera pans down to reveal that the rocking motion of the chair is smashing a photo of his stepfather.
The next day, Martin goes to Susan's house and waits for her to return. She arrives with a young Indian man named Shashee. He drops off Susan, who thanks him; she goes to the library, where she keeps an after-school job. Martin approaches Susan who immediately recognises him as Georgie. He tells her that he followed her, and pays her back for the toy. Before he leaves, Martin, as Georgie, gets Susan to lend him The Jungle Book.
Martin has a heated conversation with his stepfather, who insists he travel to Australia. Martin refuses and returns to his room. Martin stares in the mirror, bare-chested, and caresses himself. He removes the rest of his clothes as the camera reveals a stack of male bodybuilding magazines on his dresser. He then smashes the mirror in apparent frustration or anger.
Martin sets in motion a plan to leave home, pretend to go to France and then go on to live with Susan. Martin leaves his family and shows up late at Susan's mother's house, where she rents rooms. Presenting himself as Georgie, he gains sympathy both from Susan and her mother and they let him stay.
The plot unravels with Martin's duplicitous nature clashing against his desires to win Susan's heart. He wants her to accept him as a lover, but cannot reveal that he is in fact Martin, as he is worried she will shun him. Meanwhile, Martin uses his new-found identity to his advantage to seek out revenge on his stepfather, who believes he is in France. This series of decisions leads Martin down the path of self-destruction.
One night, Martin sneaks out of Susan's house after stealing a pair of scissors, and stabs his stepfather to death in the garage of his home after his stepfather comes home from a dinner party. The police investigate the next day and focus their attention to finding Martin for questioning.
A few days later, Martin invites himself to tag along with Susan who is going for a swim at a country lake where Martin attempts to kiss her until she refuses his advances, making her uncomfortable and suspicious about him. At home a little later, Susan searches Martin's room while cleaning it, and discovers several books hidden in Martin's drawer that a person with learning difficulties would not read or understand, as well as a book titled Know Yourself from Your Handwriting, in which signatures in the blank pages read 'Martin Durnley'.