Some of the video boxes for the US video release incorrectly claim that the Ian Fleming playing Dr. Watson was the Ian Fleming who was the creator/writer of the James Bond novels. Although both men have the same name - a not particularly uncommon one in England - the actor playing Dr. Watson was not the same man as the James Bond author, and was in fact not even related to him. This Ian Fleming had a 40-year career as an actor and played in over 100 British films.
This movie is based on the Sir Arthur Conan Doyle novel The Valley of Fear, and the name appears as a title reference in the movie itself. For the movie, Mr. Douglas' wives were combined into one character; in the novel, he married another woman, Ivy, after Effie died of scarlet fever.