Trick scams and thefts are part of everyday life in Rome - a world in which Nico Giraldi (Tomas Milian) is very familiar. The full-bearded long-haired man doesn't show that he is a policeman. But that is deceptive, because Giraldi, whose mother was a prostitute and who grew up in the streets of Rome, knows his crooks and knows how to get hold of them. But when two little thieves accidentally steal the briefcase from the American Norman Shelley (Jack Palance), the situation changes. Officially, Shelley does not turn on the police because there are supposedly only worthless things in the briefcase, but when the thieves open the case, they know it will be dangerous. Soon one of them will be brutally murdered ...