Maigret is called to Charenton, Lock No. 1, where the owner of barges and quarries, Émile Ducrau had been stabbed and thrown into the canal, but without being killed. Maigret goes to his house, and finds he is someone Maigret likes. Ducrau offers 20,000 francs for the solution to the crime. Maigret meets his wife, hears about his son, and Gassin, his old buddy, who runs his barge the Golden Fleece with his retarded daughter, Aline Gassin. Maigret has seen Gassin in a drunken stupor at the café. It was he who found Ducrau in the water. Maigret vists Aline, who is afraid of Ducrau. Maigret and Ducrau walk to the Pont-Neuf, where Ducrau goes into the Tabac Henri IV, a kind of freighter's bourse. While he is there a boat comes up the river with the news that his son, Jean Ducrau, has hanged himself. In a note the boy claimed he'd been the one who'd stabbed his father.
The next day Bébert, an assistant lock-keeper is found hanging from the upper lock-gate. Ducrau confronts Maigret with a newspaper article that says he will retire within a week, well before retirement age. Maigret says it's true, and Ducrau offers him a job at up to 200,000 francs a year, which Maigret refuses. At the funeral Gassin is found to be carrying a revolver, and he is arrested and the gun taken away. Maigret has him released. Ducrau has confided to Maigret that Aline is his daughter. He invites Maigret to Samois, his country house on the Seine. Gassin appears nearby, followed by Lucas. Ducrau invites him in, and admits that he killed Bébert when he found him spying on Aline. During the night Gassin hangs himself. Ducrau is looking forward to a few years rest in jail, for faking the attack upon himself.
The review of this Book prepared by Dana Samson