Beverly Hills divorce lawyer Stephen Blume (George Segal) has fallen deeply in love with his ex-wife, Nina (Susan Anspach), but she has moved on and become involved with Elmo (Kris Kristofferson), a groovy out-of-work musician. Although Stephen has a new sex partner, divorcée Arlene (Marsha Mason), he feels incomplete without Nina. Despite attempts to cover up his feelings, Stephen finds it difficult to control himself, invading Nina's privacy, attempting to befriend Elmo, and behaving desperately to win back the love of his life. Returning to Venice six years after his honeymoon there, Stephen ponders the events leading to the destruction of his marriage.