For years now, Chief inspector Gustave Picard has been trying to bring down Salviati, the dreadful leader of a drug-selling gang. Lucienne Préville, an informer who works for him, has infiltrated the gang but her position is dangerous. On the other hand, Scoppa, Salviati's former right-hand man, has started challenging his former boss. Will Salviati, the brutal public enemy, clear off at last?

Pour démanteler un réseau de drogue, le commissaire Picard infiltre les deux bandes rivales avec l'aide d'une indicatrice, Lucienne Réville. Découverte, elle est tuée par Salviati, l'un des chefs des trafiquants...