- Directors: Alfred Hitchcock
- Producers: Associate producer, William Hill, Uncredited, Alfred Hitchcock
- Writers: Stage play amp screenplay, Frederick Knott
- Genres: Crime, Mystery, Thriller
- Actors: Ray Milland, Grace Kelly, Robert Cummings, John Williams, Anthony Dawson
Tony Wendice (Ray Milland) is a former tennis player who married Margot (Grace Kelly) partly for her money. To please his wife, he has given up tennis and now sells sports equipment. Margot once had a relationship with Mark Halliday (Robert Cummings), an American crime novelist, but broke it off when Mark went to the U.S. for a year. In time, they stopped writing to each other.
Tony and Margot have made their wills, naming each other as beneficiary. For a year, Tony meticulously plans Margot’s murder. She has no idea that Tony knows of her love for Mark. He has gone to great lengths to steal a handbag containing one of Mark’s letters, and even assumed the role of an anonymous Brixton-based blackmailer to find out whether she would pay to have it back. (She did, but he asked for only ВЈ50.) He even watched them having a little farewell party (eating spaghetti with mushrooms) in Mark’s studio flat in Chelsea.
Tony slyly withdraws small amounts of money for a year, collecting ВЈ1,000 in (used) one-pound notes, with which he plans to pay a contract killer. He singles out the perfect man to do the job: C. A. Swann (Anthony Dawson), who now calls himself “Captain Lesgate”, a former acquantaince who has embarked on a life of petty crime since even before leaving Cambridge where he and Tony were both students. By following him and finding out about his past and associations, Tony soon gets enough to blackmail Swann into murdering his wife.
Tony enters the room to find Margot and the inspector, and Mark too. He realizes he’s been found out and congratulates the inspector. He then offers everyone a drink, acting very casual, as tears begin to stream down his wife’s face. The last scene is of the inspector, acting in a manner that shows he’s proud of himself, as he combs his mustache.