William Gridley (Jack Lemmon) is an American diplomat who takes a room upon his arrival in London. Carlye Hardwick (Kim Novak) is the lovely landlady mixed up in a jewel heist orchestrated by husband Miles (Maxwell Reed). Caryle lets on that her husband is dead, and she falls for her new tenant. Comedy and suspense follow the couple when her supposedly dead husband returns and demands the jewels she has pawned. Fred Astaire plays William's diplomatic boss. Screenplay written by Larry Gelbart and Blake Edwards from the story by Margery Sharp.