While visiting her sister in Rome, married American Mary Forbes (Jennifer Jones) becomes entangled in an affair with an Italian professor, Giovanni Doria (Montgomery Clift). When she prepares to leave Italy, Giovanni confesses his love for her. The two have carried on a one-month affair, and Mary must decide whether she wants to return to her husband and family. Or continue her romantic liaison with Giovanni. Will she throw away her old life for this passionate new romance?