- Career Resurrection: The film revived the faltered career of Ida Lupino, whose Hollywood roles were dwindling. It was in fact a radio performance on Orson Welles' "Mercury Theatre of the Air" that brought her to the attention of a Fox casting agent, who was impressed with her clear voice and mid-Atlantic delivery.
- What Could Have Been: Lionel Atwill, who had played Dr. Mortimer in "The Hound of the Baskervilles", was originally announced to be in the film in early press releases (probably as Moriarty), but didn't end up being cast.
- Working Title: Sherlock Holmes.
Trivia / The Adventures of Sherlock Holmes (1939)