Beautiful young housewife Séverine Serizy (Catherine Deneuve) cannot reconcile her masochistic fantasies with her everyday life alongside dutiful husband Pierre (Jean Sorel). When her lovestruck friend Henri (Michel Piccoli) mentions a secretive high-class brothel run by Madame Anais (Genevieve Page), Séverine begins to work there during the day under the name Belle de Jour. But when one of her clients (Pierre Clémenti) grows possessive, she must try to go back to her normal life.