When aging womanizer Harry Sanborn (Jack Nicholson) and his young girlfriend, Marin (Amanda Peet), arrive at her family's beach house in the Hamptons, they find that her mother, dramatist Erica Barry (Diane Keaton), also plans to stay for the weekend. Erica is scandalized by the relationship and Harry's sexist ways. But when Harry has a heart attack, and a doctor (Keanu Reeves) prescribes bed rest at the Barry home, he finds himself falling for Erica -- who, for once, may be out of his league.