Police Comissioner Datti is investigating the murder of a female doctor whose murderer seems to be a thirty-fivish year old man. Soon another murder follows: Pianist Robert Dominici's girlfriend is found killed. The killer also challenges Datti on the phone and says he can't be caught since he has a secret which makes him invulnerable. In the meantime the clues seems to point in strange directions...
| Production | Gianfranco Clerici | Producer |
| Production | Pietro Innocenzi | Producer |
| Directing | Ruggero Deodato | Director |
| Writing | Gigliola Battaglini | Screenplay |
| Writing | Gianfranco Clerici | Screenplay |
| Editing | Daniele Alabiso | Editor |
| Writing | Vincenzo Mannino | Screenplay |
| Production | Vincenzo Mannino | Producer |
| Sound | Pino Donaggio | Original Music Composer |
| Camera | Giorgio Di Battista | Director of Photography |
