The bulk of this film was shot in mid-1967 (shooting title "Operation M"), including all footage with Broderick Crawford, Scott Brady, Kent Taylor and John Carradine. Production finally wrapped in 1969 with biker footage featuring Robert Dix, whose name is only listed in the opening credits. Apparently, the addition of the cyclists was the only way the producers could get their picture released. This was one of seven completed features awaiting distribution when Al Adamson and Samuel M. Sherman formed their company, Independent-International Pictures Corp., beginning operations in 1969.
The title to the spy film starring John Gabriel, Broderick Crawford and Scott Brady was The Fakers, and was never completed. Taking footage from The Fakers, the director, Al Adamson, hired actor Robert Dix to play a biker (he was also a biker in Adamson's Satan's Sadists the same year). Dix's character sporadically interacts with an actress they called-back from The Fakers to tie the Espionage and Biker movie together, and the film's title was changed to Hell's Bloody Devils.
Reissued theatrically on multi-feature bills in the early 1980s as 'Nightmare in Blood'.
Shot in 1967, not released until 1970.