The fourth of 14 films based on Arthur Conan Doyle's fictional consulting detective Sherlock Holmes starring Basil Rathbone as Sherlock Holmes and Nigel Bruce as Dr. Watson.
The lines that Holmes quotes at the end of the film are a condensed version of William Shakespeare's lines from "Richard II" [ 2.1, 40-51].
The set used for Prof. Moriarty's hideout was used as a pub/bar in Sherlock Holmes and the Voice of Terror (1942).
Lionel Atwill, who plays Prof. Moriarty, earlier played James Mortimer in The Hound of the Baskervilles (1939).
Although credited as an adaptation of Arthur Conan Doyle's short story "The Adventure of the Dancing Men", the plot is an original story based on historical events (namely, the development of the Norden bomb sight, which allowed for far greater accuracy when bombing from high altitudes during daylight hours) which happened after Doyle's death. The only resemblance to the credited story is a cameo by the secret code of stick figure drawings. There is another moment taken from Doyle's "Sign of Four", and is a parallel to the sniffer dog's getting confused by two scent-trails of creosote. The trail of luminous paint is confused when some of the paint is picked up by the wheels of another vehicle at a crossroads and re-distributed for a distance in the wrong direction. And, of course, luminous paint is also a prominent detail in the most famous of all the Holmes tales, "The Hound of The Baskervilles".