A pickpocket steals Maigret's wallet only to contact him the following day, returning the stolen items on the condition that he come to the thief's apartment. When the agitated young man leads Maigret to the body of his wife, dead of a gunshot wound to the head, he implores Maigret to take the case. In this 1967 mystery, the inspector's knowledge of Paris's underworld will be put to the test.