Diane Keaton stars as Carol Lipton, a bored Manhattan housewife who becomes convinced that her next-door neighbour has committed a murder. When her sceptical husband Larry (Woody Allen) rejects the idea, Carol turns to a flirtatious friend (Alan Alda) to help her search for clues. And as their enthusiasm for the case grows, so does their interest in each other. Spurred on by jealousy and by a seductive writer (Anjelica Houston) who also excited by the mystery Larry reluctantly joins the chase, only to learn that much more than his marriage is at stake.