Henry Daniell, who plays Anthony Lloyd in the film, later played Professor Moriarty in The Woman in Green.
As in nearly all television series from the 1950s up until about the 1990s, the opening credits to the twelve Basil Rathbone-Nigel Bruce Sherlock Holmes films made by Universal, and set in what was then modern times, were almost identical, with the camera first panning upwards from the floor to show Holmes and Watson, and the moving shadows of both shown for the rest of the credits. The same opening music was used in all twelve films.
Debut of Thomas Gomez.
References the code from Sir Arthur Conan Doyle's original Sherlock Holmes story, 'The Adventure of the Dancing Men'.
The last lines in the movie are taken from the Arthur Conan Doyle story "His Last Bow," which is set on the eve of the First World War.
The scene in which a train goes off the tracks early in the film is footage from The Invisible Man.
This is the third of fourteen films based on Arthur Conan Doyle's fictional consulting detective Sherlock Holmes starring Basil Rathbone as Sherlock Holmes and Nigel Bruce as Doctor Watson. It is the first in the series to be taken out of the Victorian age and set in modern times. It is also the first to be produced at Universal Studios. (The previous two films were made at 20th Century Fox.)
This movie was originally going to be called "Sherlock Holmes Saves London" but the title was changed before release.