The bulk of the movie was filmed in The Chiselhurst Caves to enhance the production value, but resetting lights and moving cameras around the natural rock formations proved to be problematic and time consuming.
Originally Norman J. Warren wanted orchestral sound, but because of a lack of budget John Scott suggested electronic synthesizers.
The script was written in four days because director Norman J. Warren had financial backers and no screenplay. The film was shot in four weeks.
The story was originally supposed to take place aboard a spaceship, but they changed the location to avoid having to employ elaborate special effects.
End credits for U.S. release list several cast members who do not appear in that apparently edited version.