Maigret and the Informer (Inspector Maigret, #74)

Maurice Marcia, the ex-gangster owner of the fashionable restaurant on the Rue Fontaine, The Sardine, is found murdered in the Avenue Junot, apparently killed elsewhere. He'd left his restaurant during the late evening, after receiving a phone call. Inspector Louis, who knows the 9th arrondissement well, has received a reliable tip, via an anonymous phone call, that Manuel Mori was the killer. He and his brother, Jo Mori, are suspected of being behind the château gang, who have been doing a series of burglaries of unoccupied villas. Marcia's wife of 4 years, Line Marcia, 30 years younger than him, seems the perfect bereaved widow, but soon it appears she is actually Manuel Mori's mistress. Maigret confronts Manuel Mori, and learns the identity of the informer, a Montmartre character called the Flea, because of his size. He has gone into hiding, and even his girlfriend doesn't know where. Maigret travels south, to Bandol, for Marcia's funeral, and confronts Line and Manuel in her villa. Back in Paris, Maigret finally locates the Flea, and arrests Line, Manuel, and Manuel's brother, Jo. In Maigret's office, the Flea admits that Manuel had paid him to call Marcia, setting up the situation for the killing. Line had been at least an accomplice, and Jo Mori had helped to drive the body away to be dumped in the Avenue Junot.