A horrific and, on the face of it, incomprehensible murder has just been committed on the unsympathetic person of a loan shark. The victim's body is found lifeless, but the circumstances of his death are far from clear. For want of anything better to go on, the police immediately suspect a penniless gentleman who had the bad idea and misfortune to be present at the time of the crime. The police don't take the time to look for other possible suspects, and are not at the end of their surprises. A dark story seems to lie behind this imbroglio of incoherent facts.

In Montmartre, prostitutes and neighborhood pimps meet in Victor's bar. One of them, Charly, one day falls in love with the beautiful Laurence, a girl who honestly earns her life as a singer. But Fernand, the local boss, sees a bad eye his acolyte out of the ranks to lead a quiet life in the company of his sweetheart. He provokes the jealousy of Jessy, mistress of Charly. The latter, stung, does not intend to leave without fighting his lover take the tangent. She ruminates her revenge so much that she ends up shooting Charly ...