In England during World War II, Sarah Miles (Deborah Kerr) is the bored wife of a British civil servant. When Mr. Miles introduces her to American writer Maurice Bendrix (Van Johnson) at one of the couple's cocktail parties, she is unable to deny her attraction to him, or resist his interest in her. Almost as quickly as the two become deeply involved, Sarah mysteriously brings their affair to an end. With the help of a private detective, Maurice sets out to find out why. Based on the novel by Graham Greene.