A death that might have been a murder has occurred in a building. Carol Lipton (Diane Keaton) believes it was a murder. She is married to Larry (Woody Allen). Their neighbor, Lillian House (Lynn Cohen), whom they had just met along with her husband, Paul (Jerry Adler), is the dead person. Paul does not seem to mourn her and is moving on very quickly; this makes Carol suspect him. She thinks about some odd things that have happened and she becomes more convinced of Paul’s guilt. Their friend Ted (Alan Alda) believes Carol is right and helps her to try to figure things out. Larry will not help at first but then becomes envious and more helpful.