John Howard Barrington escapes from Alcanta, a state asylum for the criminally insane, and exhaustedly winds his way through the desert as the police chase him. He finally collapses at a turkey farm and is taken in by its owner, desert hermit Ezra Thompson. When Ezra holds John at gunpoint and warns the escapee that the police will certainly catch up with him, John attempts to take the gun from him but fails. Still friendly despite the threat of violence, Ezra listens as John expounds that insanity is a lack of knowledge between right and wrong in a particular act. Ezra asks John what his particular act was but John cannot remember. John does recount an incident at the hospital in which he witnessed a brutal strangling of another prisoner but did not help the victim. Alcanta's Warden Anderson and other officers then arrive at the ranch and Ezra hides John. Anderson explains the history of the escapee to the group, and John overhears it in the next room. John, Anderson states, is a killer and his victim was Rose Marie, his girl friend at the time. John, who was finishing a law degree, would have been given the death penalty but his loss of memory secured his immunity. Anderson tells Ezra that John does not stand a chance of escaping in the barren desert with a $200 reward on his head. After Anderson and the others leave, John emerges, wanting to know why Ezra did not turn him in. Ezra explains that he prefers the company of nature and books, and distrusting civilization, decided to give John the benefit of the doubt. Later, John's foster father, the wealthy Cyrus Barrington, and the English family psychiatrist, Dr. David Dunbar, visit Anderson and Alcanta's psychiatrist Dr. Gordon at the hospital to request that the reward be increased to $5,000. During the visit, Gordon lets out a laugh and the effeminate David becomes visibly perturbed and states that he is "allergic to irrelevant laughter." Back at the ranch, Ezra sends John, who has been working at the ranch for three weeks, into town to fetch feed. On his way John picks up hitchhiker Connie Carter, a singing waitress heading back to Level Louie's, a Los Angeles bar. Bored with looking at the sky and John's silence, Connie, whose "morals have no zipper," asks for some action during a roadside break, but John replies that he is satisfied because to him the desert is "an image of freedom." When Connie wraps a scarf around her neck, John recognizes it and adamantly asks where she got it but she refuses to answer. That evening John drops Connie at the Silver Saddle bar and later returns to find her cornered in a booth by two drunken locals. A brawl between the three men ensues but John disappears when the sheriff arrives. At the bus station Connie spots the $5,000 reward poster and contemplates going to the sheriff but, recalling John's kindness, decides to take the bus instead. At the ranch, John tells Ezra that he remembers Rose Marie was strangled with a scarf, a gift from his best friend David. Determined to find the next key to the puzzle, John seeks Connie out at Level Louie's but Connie runs him off, saying she knows about his insanity and the murder. Disconsolate but determined, John goes to David's office and David admits to him that he witnessed the murder but was unable to stop John because the shock crippled him. Barrington and the police, having been secretly contacted by David, show up and take John away. Convinced of John's innocence, Ezra and Gordon arrive at Level Louie's and enlist Connie's help to save John. Gordon then goes to David's office and tells him that "shock reaction" does not exist and, furthermore, John's reaction to the prison murder can be attributed to his unconsciously realizing it was a repeat of the previous event. Gordon tells David he knows that David suffered mental illness while serving in the English Army, and accuses him of being the killer, explaining that John was unable to react the first time because he was only partially conscious due to a severe blow to the head. After Gordon leaves the office abruptly, David turns to find Connie by the window wearing the duplicate scarf. Connie begins to laugh, upsetting David. He tells her that John and Rose Marie laughed behind his back that way and recounts how he killed Rose Marie in a fit of pique. The police, Gordon, John and Ezra are waiting at the door, and just as David is about to choke Connie, John comes to her rescue. Later at Level Louie's, John listens to Connie sing then, grateful for his freedom, leaves with Ezra to return to the turkey ranch, where it is "bound and bare" and spread with "lone and level sand."