The body of a well-known Parisian restaurateur turns up on Avenue Junot in Montmartre, having seemingly been killed elsewhere. Inspector Maigret dives into the investigation and soon discovers that the murder may be gang-related after a colleague working in the red-light district receives a tip from an anonymous informer.

Deeply engrossing, and revealing insights about the class-conscious world of the Paris elite, Maigret and the Informer draws the reader into a complicated case that could hinge on one man's word.