Margot and her adolescent son Claude take a train from New York City to Long Island, where Margot's sister Pauline is about to get married to Malcolm. Even though Margot is a successful writer with a compassionate husband, she is repressed, bitter, insecure, and angry, and she takes out her frustrations on anyone and everyone around her. Pauline is initially happy that her sister has decided to come to the wedding, but she quickly realizes that Margot is still her terrible old self. Over the course of a few days, past conflicts erupt and present conflicts explode, threatening not only to put a damper on the wedding, but to ruin it completely.