Severine Serizy, happily married to a handsome young surgeon, goes to work in a house of ill repute, actually an intimate apartment. The money involved is less the motivation than the pretext for her action. Pierre, her husband, provides for her material needs handsomely, but his respectfully temporizing caresses fail to satisfy her psychic need for brutal degradation, a need first awakened by a child molester when she was eight. To preserve a facade of marital respectability, Severine works at her obsessive profession only afternoons from two to five, the mystery of her matinée schedule causing her to be christened Belle de jour.