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.