Michel Simon, a major star in France at the time, had used some tainted makeup on a previous film that had resulted in his body and face becoming temporarily partially paralyzed. Since that time he had been unable to find work and took a role in this low-budget German horror film because he needed the money and only his head would be shown, and he didn't think a film of this caliber, which could adversely affect his career, would be seen on the rest of the continent. Unfortunately he was wrong, and the film was in fact a hit on both sides of the Atlantic.