Bruno Fioretti, known as "Mandrake", is an inveterate gambler who never misses a day at the horse racing track in Rome. He is doubly unlucky: he bets too much on one horse, and his wife is sleeping with his best friend because Mandrake is always at the track. Penniless and cuckolded, Mandrake decides to make one last bet.
Police commissioner Santamaria is investigating the murder of the ambiguous architect Mr. Garrone. The investigations soon drive him into the Torino's high society. Santamaria suspect Anna Carla and at the same time falls in love for her. Lello is the lover of Massimo, Anna Carla’s gay friend. He is following another direction in order to find out the truth, and his results are confusing the Policeman. But another murder happens...
An obscure Italian magistrate suspects that a well-known industrialist commited murder, and decides to investigate him, and bring him to court, whatever it takes. But - will the magistrate have it in him to go against impossible odds, in the name of the Italian people he represents?
