During an evening in a bar, Roger, a friendly cognac salesman and connoisseur, overhears a telephone conversation that intrigues him, then worries him: "... a few bullets to the head and she'll be dead in a minute...". Distraught, Roger follows the stranger who has taken his car. A relentless pursuit ensues. Roger arrives at a mysterious property where the "assassin" disappears to commit his crime. Knocked unconscious by the killer he fought and prevented from carrying out his crime, Roger regains his senses, comfortably installed in the living-room of an old colonel, Colonel Van Booren.

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.