Pretty Poison is director Noel Black's thriller film debut. It follows Dennis Pitt (Anthony Perkins), a psychopath on parole from his mental hospital. He finally conquers his fears of the outside world and wanders out of his house. His walk takes him around town, and he meets a young cheerleader named Sue Ann (Tuesday Weid) and falls in love. She is disinterested in him at first, but Dennis lies and tells her that he is a secret agent on a dangerous spy-hunting mission. He offers to bring her along on a series of missions, and Sue falls in love with the adventurous lifestyle. When one of these missions ends in murder, she doesn't bat an eye and says that they should escape to Mexico together, but first they have to deal with her annoying mother. Dennis realizes that his new girlfriend is more psychotic than he is, but who will believe him?