A young couple, Renée and Pierre, take a room at the Hôtel du Nord, in Paris, near the canal Saint-Martin. They want to die together, but after shooting Renée, Pierre lacks the courage to finish the job and flees. Another guest, Monsieur Edmond, rescues her. When Renée gets out of the hospital she is hired as a waitress at the same hotel. Monsieur Edmond falls in love with her, but Renée is still thinking of Pierre.

Paris, France, December 1946. Jenny Lamour, an ambitious cabaret singer, and Maurice, her extremely jealous pianist husband, become involved in the thorough investigation of the murder of a shady businessman, led by Antoine, a peculiar and methodical police inspector.