The marquis Galeazzo di Torre Alta is murdered by a mysterious killer who calls himself Diabolicus. His heirs are his three brothers and a sister, but all of them, with the exception of Monsignor Antonino di Torre Alta, are killed by Diabolicus. The police are unable to solve the case, but when Antonino gives his inheritance to Pasquale Bonocore, illegitimate son of his father and Pasquale is in prison and therefore can't be the killer, all the clues are in the hand of the police.
Totò
Galeazzo / Carlo / Scipione / Antonio / Laudomia / Pasquale
Raimondo Vianello
Barone Lallo
Nadia Sanders
Donna Fiore
Luigi Pavese
Commissario di polizia
Mario Castellani
Ispettore Scalarini
Peppino De Martino
Notaio Cocozza
Giulio Marchetti
Detective Privato
Franco Giacobini
Dottor Santoro
