In an interview included on the movie's the DVD, director Gordon Hessler said that he thought the majority of people knew the ending of the source short story (the film is a remake and had been shot more than once before), so Hessler thought he would re-imagine the story, and as such introduced new story elements.
The movie's closing credits declare that this motion picture was: "Filmed entirely on location in Spain".
Another version of the film's source Edgar Allan Poe short story, but made for television, Le double assassinat de la rue Morgue (1973), was released within a couple of years, and the previous version, also made for television, had been first broadcast only about three years earlier [See: The Murders in the Rue Morgue (1968)].
The name for the type of horror genre of plays that were staged at the "Rue Morgue Theatre" in Paris, France was "Grand Guignol". The name of the early 20th century theatre troupe that staged the plays there was "Cesar Charron's Company".