Maurice Legrand, Michel Simon, is a meek cashier and aspiring painter who longs for recognition in the art world, even as he drifts through a strained life with his wife, Adèle Legrand, Agnès Capri. Adèle’s harsh attitude toward his art colors their home, and Maurice’s gentle, dream-filled nature often clashes with her bitterness.
One evening, after a company celebration, Maurice encounters a troubling street scene: André "Dédé" Jauguin, Georges Flamant, strikes Lucienne “Lulu” Pelletier, Janie Marèse, a prostitute, who defends herself in kind. Maurice steps in and ends up accompanying them as they wait for a taxi. After Dédé is dropped off at his residence, Maurice walks Lulu home, and she confides that Dédé is her pimp, a relationship she’s known for three years. This fateful encounter plants the seed of Maurice’s later entanglement with Lulu, a relationship that will pull him deeper into a world of art, money, and danger.
Back home, Adèle questions Maurice about his lateness and degrades his paintings, insisting they clutter their apartment. A month passes, and Maurice rents a separate apartment for Lulu, treating her as his mistress and filling the space with his own canvases, trying to nurture the art he believes he could achieve while Adèle lingers in the background of his life.
Lulu and Dédé soon devise a plan to exploit the paintings, claiming they have a connection to the works. They move to pass the paintings off under Lulu’s name, even inventing an American alias, “Clara Wood,” to add an air of legitimacy. Weeks go by, and Maurice’s own paintings surface again when his employer directs him to an art store where the works are suddenly displayed. Lulu, maintaining a deceptive front, persuades Maurice to claim that she and her fictitious brother had sold the paintings to Wallstein, Lucien Mancini, an influential collector.
The paintings gain acclaim, and Lulu and Dédé’s finances improve as the critics praise the works as if they were Lulu’s, a lie sustained by Maurice’s growing complicity in their scheme. In the midst of this, Maurice encounters Alexis Godard, the former husband of Adèle, who—having survived the war by switching identities and enduring imprisonment—appears alive and penniless. Alexis reveals his survival and begs Maurice for one thousand francs, money Maurice knows Adèle has hidden away.
Maurice hatches a plan to have Alexis steal the money, promising to attend a theater the following night as a cover. The ruse succeeds long enough for Adèle to call the police, but Maurice then admits to the officers that Alexis is alive. Free from immediate arrest, Maurice heads to Lulu’s apartment, only to discover Lulu and Dédé together in bed. He leaves in shock, but returns the next morning to confront Lulu. She confesses that she loves Dédé and reveals that the only reason she remained with Maurice was his money. In a moment of despair and humiliation, Maurice stabs Lulu and departs, leaving no witnesses.
Lulu’s body is eventually found, and both Maurice and Dédé are questioned. The interrogator’s view of their criminal histories buys Maurice a measure of exoneration, while Dédé is charged with Lulu’s murder, found guilty, and executed. Maurice, meanwhile, is accused of mismanaging 2500 francs by his employer and is fired under the guise of health problems. He drifts through the streets as a vagrant, a shadow of the man he once hoped to be. A chance reunion with Alexis reveals that Adèle has died, leaving Maurice with little but his own dwindling hopes.
As a car carries Maurice’s self-portrait through the city, he and Alexis manage to scrape together a meager 20 francs on the street, and they walk away together, two men who have learned the hard irony of art, money, and ruined dreams.
