L'amour c'est gai, l'amour c'est triste

In a cul-de-sac in the Faubourg-Saint-Antoine, Leon shares two rooms with his sister Marie. In one, he receives his clients: he is a tailor. In the other, Marie receives her own: she is a clairvoyant. Leon was happy until he learned what Marie was hiding from him. She is actually a prostitute, and Maxime, her supposed fiancé, is her pimp. On the same day, Leon also discovers love in the form of Arlette, a provincial young woman picked up by Marie.