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.
Unfortunately the movie Totò diabolicus is not yet available on HBO Max.
| Directing | Steno | Director |
| Writing | Vittorio Metz | Story |
| Writing | Vittorio Metz | Screenplay |
| Writing | Marcello Fondato | Screenplay |
| Editing | Giuliana Attenni | Editor |
| Writing | Bruno Corbucci | Screenplay |
| Directing | Mariano Laurenti | First Assistant Director |
| Art | Giorgio Giovannini | Production Design |
| Costume & Make-Up | Giuliano Papi | Costume Design |
| Art | Brunello Serena Ulloa | Set Decoration |
| Directing | Renata Clerici | Script Supervisor |
| Camera | Enzo Barboni | Director of Photography |
| Writing | Roberto Gianviti | Story |
| Directing | Mario Castellani | Second Assistant Director |
| Camera | Stelvio Massi | Camera Operator |
| Writing | Giovanni Grimaldi | Screenplay |
| Production | Gianni Buffardi | Producer |
| Writing | Roberto Gianviti | Screenplay |
| Sound | Enzo Silvestri | Sound |
| Costume & Make-Up | Maria Miccinilli | Hairstylist |
| Costume & Make-Up | Sergio Angeloni | Makeup Artist |
| Editing | Marcella Bevilacqua | Assistant Editor |
| Camera | Renato Fait | Assistant Camera |
| Production | Egidio Quarantotto | Unit Manager |
| Production | Franco Pranteda | Production Secretary |
| Production | Giancarlo Sambucini | Unit Manager |
| Sound | Piero Piccioni | Original Music Composer |