Maigret is called to the home of René Josselin, a retired cardboard box company owner, who has been found shot in his chair at home. His wife, Francine Josselin and daughter, Véronique Fabre, had found him when they returned home from an evening at the theater. He had stayed home, and played chess with his son-in-law, Doctor Paul Fabre, who'd been called away to a sick child, but there was no sick child, and no one at that address knew anything about it. The problem is that everyone involved is a "good person" and there are no suspects, and no motive. According to the concierge, no one had left the building after Dr. Fabre, and only one person had come in, for one of the neighbors. But then it seems Josselin's gun is missing, and the neighbor reports no visitors. A search of the building reveals that a man had stayed in one of the maid's rooms, and that he'd gotten the key from the Josselin's apartment. The door hadn't been forced, and Josselin wasn't taken unawares. Finally a tedious door-to-door check of the neighborhood reveals that Josselin had met a man in a café one day, and that his wife had met the same man later on. Maigret discovers an old lady who'd known Mme Francine Josselin's family before she married, and that she had a younger brother, who had always been in trouble. She confronts Mme Josselin, who admits she hadn't wanted to mention her brother, no doubt the killer, who'd apparently come to borrow money from Josselin once again, and shot him in anger when refused. A search for the man, Philippe de Lancieux, is unproductive, until six months later he is found dead, knifed in some kind of underworld crime.