Only 10 days after the arrest of the dentist in the Rue des Acacias, Maigret finds himself there again, this time investigating the murder of Manuel Palmari, a criminal Maigret had known for 20 years, and who he suspected to be behind the string of jewel robberies over that period. Palmari's mistress Aline was out shopping at the time, with a police tail. Maigret interviews almost all the tenants of the building, then goes to the Palmari's Clou Doré restaurant with Lapointe, and talks to the new owner, manager and headwaiter, Jean-Loup Pernelle, who tells Maigret of a hotel Palmari owned. While there he notices a certain Mr. Louis, and he leaves Lapointe to watch him.
After Maigret leaves, Mr. Louis makes a phone call, and Lapointe sees most of the number. A check reveals that it's to the tenant opposite Manuel Palmari's apartment, Fernand Barillard. Maigret goes to the hotel, learns it is owned by Aline, and that she met Barillard there. Maigret goes to visit him, and tells him he knows he and Aline are behind the crime, then goes and tells Aline the same thing.
Later, while talking to someone in the diamond district, Maigret realizes the significance of the deaf-mute in the attic, Jef Claes. He rushes back to the building, but he is too late: Jef has been hanged in the basement shop, belonging to Barillard. Barillard's wife, the former Mina Claes, had been Jef's adopted granddaughter, from when they were bombed in Douai during the war. Barillard had enlisted him as the gang's diamond cutter. Maigret arrests Barillard and Aline, allowing them to meet at the Quai Des Orfevres where they attack each other.
This report prepared by Dana Samson