Thomas, a struggling former magician, and Carlo, a Neapolitan submissive to his Northern wife and father-in-law, are two half-brothers who reunite after years in Naples following the death of their father, Vittorio, an inveterate gambler and womanizer. They discover they have a third brother, Ugo, who appears a bit dim-witted but is actually a genius. The inheritance Thomas and Carlo covet disappears due to their father's debts, and the three have a brilliant idea: to exploit Neapolitan superstition and credulity by becoming "ghostbusters." Just when their business seems to be unexpectedly successful, the spirit of their father, Vittorio, takes possession of Carlo's body. Thomas and Carlo become convinced that ghosts really do exist. Meanwhile, the ghosts captured by the trio break free and go to awaken the ghost of a witch who threatens to destroy Naples. With their father's help, the three brothers try to save the city.