A body has been found, dumped in the Bois de Boulogne, face battered. Aristide Fumel, Maigret's old colleague from the 16th, calls him about it, though under present rules the Public Prosecutor's office is bound to feel it's outside of Maigret's province, and besides, he's supposed to be working on the rash of robberies. But Maigret goes to the park and recognizes the body, Honoré Cuendet, a quiet burglar Maigret had known for 30 years. Maigret goes to Justine Cuendet's, Honoré's mother's, to let her know. The only clue, a couple of wildcat's hairs, as from a car rug, had been found on his jacket. This unofficial investigation of Maigret's is interrupted when a robbery takes place on the Rue La Fayette, and an off-duty constable on the scene had shot one of the robbers. It seems like finally a break into the gang, which Maigret believes to be headed by Fernand, recently released from prison, whereabouts unknown.
Meanwhile Fumel has picked up Cuendet's trail — he'd been living in a little hotel on the Rue Neuve-Saint-Pierre, opposite the mansion of Mrs. Florence Wilton. Apparently that was his next target. Maigret sends a man to keep watch from Cuendet's hotel room. On the robbery case, some connections have been made to the wounded man's associates, especially his friend René Lussac, who spends time in the Café des Amis near the Porte de Versailles. Maigret inquires about the Wilton's, but is told that investigating them wouldn't be a good idea, as Stuart Wilton is "a good friend of France". A trace of a call made by Lussac leads to a villa outside Corbeil, where it appears Fernand is probably holed up. A simultaneous raid is planned for the villa and the Café des Amis, and it is successful, while in Montmartre, Lognon has recognized Cuendet's picture, leading Maigret to his girlfriend, Éveline Schneider. Engough evidence — the stolen money — is accumulated in the robbery to make a case for the arrests. Maigret is convinced that Cuendet had been caught in the act by Stuart Wilton's son, his ex-wife's mistress, and killed so that he wouldn't be able to reveal the relationship. The lack evidence and social position of the probably culprits make it worthless to follow up. Maigret tells Éveline that there should be some money for her and Cuendet's mother somewhere among his things.
The review of this Book prepared by Dana Samson