In the dialogue, it is revealed that both Holmes and Watson are in in their mid-fifties. In reality, Christopher Lee and Patrick Macnee, both born in 1922, were about 70 years of age at the time of this production.
Christopher Lee starred in five other Arthur Conan Doyle filmed adaptations or related filmed productions. They are Le Chien des Baskerville (1959), Sherlock Holmes et le Collier de la mort (1962), La vie privée de Sherlock Holmes (1970), Sherlock Holmes and the Leading Lady (1991) and The Leather Funnel (1973).
Jenny Seagrove previously starred in The Sign of Four (1987) alongside Jeremy Brett's Sherlock Holmes. She also starred in Rendez-vous avec la mort (1988) with the world's second most famous literary detective, Hercule Poirot, there played by Peter Ustinov.
Claude Akins appeared as President Theodore "Teddy" Roosevelt in this movie and The Gambler Returns: The Luck of the Draw (1991).