Michel Piccoli plays a police inspector whose best friend is murdered on the orders of gang boss Charles Vanel. The inspector knows full well that Vanel is too crafty and well-connected to ever stand trial for his crime, so he carefully lays a subtle trap for his adversary. Unfortunately, both Piccoli and Vanel are thwarted by a pair of scheming females.

Géo Paquet, aka The Gorilla, breaks from jail. Now an escaped convict, the elite agent must infiltrate a dangerous gang working for a foreign embassy as their leader, a spy enjoying diplomatic immunity, can't be arrested by regular police.