Zélie de Chaumet (Jeans) is a bored, sensation-seeking Demimonde, living with her older lover and keeper Herman Stetz (Robert Scholtz) in a lavish apartment in a wealthy area of Paris. By contrast career criminal Pierre Boucheron (Novello), known as The Rat, lives with his casual girlfriend Odile (Marsh) in a run-down room in a squalid part of the city.