Carl and Elsa are a young married couple who live in a trailer near a highway on the beach in California. Carl works and therefore is away from the trailer all day, leaving Elsa alone. Carl is disturbed about this and warns Elsa not to go on the beach unless there are other people about. As Carl leaves, he asks a nearby, friendly neighbor, Mrs. Ferguson, if she will keep an eye on Elsa. Mrs. Ferguson learns that Elsa was formerly a ballet dancer who had a nervous breakdown. When Mrs. Ferguson calls on Elsa, she suggests that it is not wise for the trailer to be parked away from the others, and underneath a dark tree, for there are hitchhikers and others who may be dangerous. Mrs. Ferguson invites Elsa to go to town with her for some shopping, but Elsa refuses, for she wants to be home in the trailer when Carl returns from work. Mrs. Ferguson leaves, warning Elsa to be sure to keep the door locked. Later, that night, when Carl returns home from work, he finds a cake in the oven burned to a crisp and the trailer is in shambles. Elsa is unconscious. When Elsa is revived, she tells Carl that a man appeared in the doorway and she becomes hysterical saying that the man has killed her. Mrs. Ferguson, hearing the commotion, calls a doctor and the police. But Carl, knowing that this will upset the already hysterical woman, refuses to allow the doctor examine Elsa and also turns away the police. Carl learns from Elsa that the man who assaulted her was wearing a grey suit and she would remember him if she saw him again. Carl takes Elsa driving where she eventually sees and remembers the man. Carl follows the man and kills him. When he returns to Elsa she sees another man, completely unlike the man that Carl has just killed, and proclaims he is the man who assaulted her. What has Carl done?