Gena Rowlands as a young wife who is about to embark on an affair. When she is alone with her new lover she realises she can't go through with it and decides to tell him. Unfortunately she realises he is dead. DFoin the right thing she phonesthe police without revealing her identity. The man's wife, who is a friend of hers, makes it her main task in life to discover the idenity of the mysterious woman and make her pay.