|Tony Musante||Sam Dalmas|
|Eva Renzi||Monica Ranieri|
|Enrico Maria Salerno||Inspector Morosini|
|Mario Adorf||Berto Consalvi|
|Umberto Rano||Alberto Ranieri|
|Raf Valenti||Professor Carlo Dover|
An American writer, Sam Dalmas, is living in Rome with his girlfriend, Julia . While visiting an art gallery, Sam witnesses an unsuccessful murder attempt by a mysterious figure. As the assailant is believed to be an infamous serial killer, Sam quickly becomes a key witness in the ongoing police investigation. After he begins searching for clues that may help him identify the killer, Sam discovers that he may be the next intended victim.