El detective Sherlock Holmes (Basil Rathbone) encara su mayor desafío cuando el genio del mal, el profesor Moriarty (George Zucco), planea robar las joyas de la corona.
 | Basil Rathbone | Sherlock Holmes |
| Nigel Bruce | Dr. John H. Watson |
| Ida Lupino | Ann Brandon |
| George Zucco | Profesor Moriarty |
| Alan Marshal | Jerrold Hunter |
| Terry Kilburn | Billy |
| Henry Stephenson | Sir Ronald Ramsgate |
| E.E. Clive | Inspector Bristol |
| Arthur Hohl | Bassick |
| Peter Willes | Lloyd Brandon |
| May Beatty | Mrs. Jameson |
| Mary Gordon | Mrs. Hudson |
| Holmes Herbert | Justice |
| George Regas | Mateo |
| Mary Forbes | Lady Conyngham |
