Strangers on a Train (1950) is a suspense thriller by Patricia Highsmith, based on the premise that two strangers swap murders. The novel has been adapted multiple times, most famously by Alfred Hitchcock in his 1951 film. Highsmith is known for telling stories in which relatable characters are coerced into crime, although in an interview with Diana Cooper-Clark, Highsmith rejected the idea that just anyone can commit murder. 

On a train from New York to Metcalf, architect Guy Haines hopes that he will soon be able to divorce his wife, Miriam, who has been unfaithful, and marry Anne Faulkner, whom he loves. Guy meets Charles Anthony Bruno on the train. They dine together, and Bruno drunkenly tells Guy he wishes his father were dead so that he can claim his substantial inheritance. Bruno suggests that Guy would be free with Miriam dead, and then puts forth the notion of swapping murders. He argues that this would be the "perfect crime," because there would be no motive for either murder.

Guy does not take Bruno seriously and hopes not to see him again. While Guy is in Mexico with Anne, Bruno kills Miriam, strangling her at an amusement park. Guy learns of the murder, and suspects Bruno after the latter bombards him with communications threatening to frame Guy for Miriam’s murder. Guy feels trapped, so instead of going to the police, he ignores Bruno. Guy's life with Anne, and as a successful architect, is now blighted by Bruno. Bruno sends Guy detailed murder plans and a gun, and anonymous letters to Guy’s friends and colleagues implicating him in Miriam’s murder.

Stricken with guilt and afraid of losing everything, Guy complies and kills Bruno's father. Several clues are left behind at the murder scene, and Guy's face is scratched. Guy's guilt, along with his horror of Bruno, increase, but the two men are now irrevocably connected by their crimes. Bruno continues to impose himself on Guy, turning up uninvited at Guy's wedding to Anne. Simultaneously, the murder investigations are underway. Private detective Arthur Gerard suspects Bruno of his father's murder and discovers that Guy and Bruno men met on the train, linking the two murders. Gerard also postulates that Bruno murdered Miriam. 

The newlyweds move to Canada, and Anne becomes pregnant. Bruno forces himself into their social circle and they all go sailing together. As usual, he gets drunk, and accidentally falls overboard. Guy jumps in after him, but Bruno drowns. The murder investigation concludes, but Guy's guilt does not. Guy is driven to confess his crimes to Miriam's former lover, Owen Markham. When the two men talk, however, it transpires that Owen did not love Miriam and is unconcerned by Guy's crime. Unbeknownst to them, Detective Gerard has overheard Guy's confession. Confronted by Gerard, Guy turns himself in.