Four murders in forty-eight hours happen in Nice. The murderer calls himself "The Exterminator" and the police are unable to catch him. Tom Lepski is an insurance detective and he get involved in the investigation when Liza Mendoza, a famous violinist and a friend, is killed just a few minutes before Tom visit her. After another rich woman killing, Tom finds out that all the victims were members of the exclusive Fifty Club. All of them but Lisa.

Genial and deceptively tentative insurance company detective Tom Lepski sets out to track down a valuable medieval Russian icon, stolen by master thief Bradley.

Patterning himself after the American gangster John Dillinger, the criminal (Robert Hossein) is tracked by the inspector (Charles Aznavour), a former childhood friend. Plenty of gunplay and psychology is used to trap the killer. His only tender moments are spent with his girlfriend Stella (Virna Lisi). Dillinger is cornered by the police and kills several innocent victims in a crowd during the shootout. The mob decides to take things into their own hands as they approach the doomed man with a noose when he runs out of bullets.