Also on the German DVD interview, Robert Hossein said that the dinner scene at the Rogers house was directed by Sergio Leone.
Robert Hossein intended the film to both a tribute to Sergio Leone's Dollars Trilogy - A Fistful of Dollars (1964), For a Few Dollars More (1965) and The Good, the Bad and the Ugly (1966) - and a starring vehicle for himself and his friend Michèle Mercier, who was wanting to break away from being typecast as a result of her performance as the title character from Angélique (1964).
On an interview included on the German DVD, Robert Hossein claims that Dario Argento was not involved in writing the screenplay. Dario Argento is listed in the credits on the Italian and German versions but not on the French version.
Final film of Béatrice Altariba.