The plot may have been inspired by a legend associated with Scotland's Glamis Castle, the ancestral home of the House of Bowes-Lyon. According to the legend, a rightful heir to leadership of the noble house was born horribly deformed, and the Bowes-Lyon family told the outside world he had died at birth. He was then kept sequestered in a secret part of the castle until his death from old age, while the next-born eligible heir took his place in the succession to family leadership.
This was to be the second 3-D film designed and directed by William Cameron Menzies. Contrary to some opinion, there is no evidence to substantiate that his previous film, Invaders from Mars (1953), was designed nor planned for for 3-D, and certainly was not shot in this process. Menzies, who was known as a director with a very "dimensional" style (eg. many shots are focused in layers), only directed one other 3-D film previous to this: "Fun in the Sun," a short that was shot for the aborted Sol Lesser production, "The 3-D Follies". This would be his final film as production designer and director.
The film is based on the 1945 book of the same name by Maurice Sandoz, which was illustrated by the surrealist Salvador Dali.
Perhaps the first film to mention the scientific discipline of teratology, and perhaps the first to discuss the now-discredited concept of prenatal phylogenetic evolution.
Last feature film directed by William Cameron Menzies.