Gig Young met his fifth wife, German actress Kim Schmidt on the set of this movie. She plays a Police Officer. A little over one year later, Young murdered her and then killed himself for reasons unknown.
Lead characters William Sebastian and Dr. "Ham" Hamilton were modelled after Sherlock Holmes and Dr. Watson.
Gig Young was noticeably drunk throughout the production and frequently slurred his lines. His drinking problem was written into the script.
Lilith, the mysterious housekeeper for Sebastian, was played by Majel Barrett, wife of Gene Roddenberry, Executive Producer and Writer of this movie.
The jet seen in the film, tail number G-BFAN, is a Hawker Siddeley HS 125.700.