Shooting lasted from April 11-May 1, 1944, released September 22.
References Sir Arthur Conan Doyle's original Sherlock Holmes story, 'The Adventure of the Six Napoleons'.
For some curious reason, Holmes' cluttered Baker Street apartment has a photograph of a beardless Abraham Lincoln.
Rondo Hatton would play a different Creeper in two films not related to this one - "House of Horrors" and "The Brute Man" - both completed in 1945, and released following Hatton's death, which occurred on February 2, 1946.
The character of the Creeper, played by Rondo Hatton, would be paid a fond tribute many years later in The Rocketeer (1991), in the character of Lothar, played by Tiny Ron.