The film was shot in three languages (French, English and Italian) with the same cast.
In the New York hideout, Alain Delon sees a poster with a female singer who he was about to kill when he played in "Le Samurai".
The hijacked plane supposedly "lands" on Route 80 in western New Jersey (Netcong exit shown) which was still being completed at the time.
Catherine Watteau's debut.
Young actor Marc Porel plays Sergio, one of Jean Gabin's henchmen. Marc's father, Gérard Landry, appeared in The Human Beast (1938) as a man with his sites on Simone Simon, with whom Jean Gabin was having an affair. Marc took the last name of his actress mother, Jacqueline Porel.