La Chienne

Cashier Maurice Legrand is married to Adele, a terror. By chance, he meets Lucienne, "Lulu", and make her his mistress. He thinks he finally met love, but Lulu is nothing but a streetwalker, in love with Dede, her pimp. She only accepts Legrand to satisfy Dede's needs of money. Remade as Fritz Lang's Scarlet Street with Edward G. Robinson and Joan Bennett.

From Criterion.com:
Jean Renoir’s ruthless love triangle tale, his second sound film, is a true precursor to his brilliantly bitter The Rules of the Game, displaying all of the filmmaker’s visual genius and fully imbued with his profound sense of humanity. A hangdog Michel Simon cuts a tragic figure as an unhappily married cashier and amateur painter who becomes so smitten with a prostitute that he refuses to see the obvious: that she and her pimp boyfriend are taking advantage of him. Renoir’s elegant compositions and camera movements carry this twisting and turning narrative—a stinging commentary on class and sexual divides—to an unforgettably ironic conclusion.