Professor Moriarty is planning to steal the crown jewels and to ridicule Sherlock Holmes in the process. This, the second film made in the Rathbone/Bruce series, pits Holmes and Moriarty together in a battle of wits; Holmes admits "in all my life I have encountered only one man whom I can truthfully call the true genius of evil-Professor Moriarty. For eleven years he has eluded me. All who have opposed him are dead. He is the most dangerous criminal England has ever known". Also starring Ida Lupino and George Zucco as Moriarty. The film reaches a dramatic climax in the Tower of London as Holmes chases Moriarty to a final confronation.