Mister Joaquim Pelletier and his wife request the services of the private detective Pepe Carvalho to find the murderer of their only son, Mariano. As the investigations progress, Pepe finds out that Mariano was not such a model son as his father thought. He had a double life: a banker at daytime, a thug at night; he was cooperating with Jesús Arquimedes, the boss of the underworld, by doing illegal works for him. But Mariano had decided to betray Arquímedes, embezzling $500 000 of the money he w...