This movie's abrupt conclusion was not the original ending. In the original script, the character of Father Rayner recovers from the rock, thrown by John Verney, and attempts to pursue Verney and Catherine. He is then struck by a flash of lightning as he crosses the circle. Although this ending was filmed, none of the footage survives and is illustrated on the DVD by monochrome stills.
This movie was released in the U.K. just forty days after Nastassja Kinski's fifteenth birthday, making it a virtual certainty she was only fourteen when her scenes were shot. In a 1997 interview, Kinski admitted feeling "torn apart" by the pressure to appear nude, and regretted there was no one present to protect her.
Screenwriter Christopher Wicking thought that the original novel by Dennis Wheatley was extremely bad and had no compunction about changing it extensively. His script was, in turn, re-written by others, mostly during shooting, and he pronounced himself dissatisfied with the movie, especially the ending.
Two high-priced British actors were cast as David and George de Grass but because Richard Widmark's fee was higher than expected, the roles of David and George de Grass were re-cast at the last minute.
The line of dialogue spoken by Father Michael Rayner (Sir Christopher Lee), "It is not heresy . . . and I will not recant!", was later sampled for the song "Super-Charger Heaven" by heavy metal band White Zombie.
The closing credits quotation from the source author reads: "In light all things thrive and bear fruit . . . In darkness they decay and die that is why we must follow the readings of the lords of light - Dennis Wheatley".
The ellipses seen on promotional materials ("To the Devil . . . a Daughter") do not appear in the title at the head of the movie, where it is spelled "To the Devil a Daughter". Also, the source novel spelled the title as "To the Devil - a Daughter".