Pierrette Dumortier, a woman of character but weak-willed and defenseless against boredom, decides one fine day to leave her husband and her bourgeois life in Switzerland to return to Paris. She settles in the studio of her son in the suburbs, finds work in a college, meets the reconstituted rich family of his daughter, falls in love with a priest, sleeps with the fiance of his daughter and, after several adventures, is manipulated by a shady antiquarian, which will lead her to prison.