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?