In Sherlock Holmes and the Secret Weapon, Sherlock Holmes (Basil Rathbone) pretends to be a Nazi spy to aid scientist Dr. Franz Tobel (William Post Jr.) whose new invention, the "Tobel Bombsight," could turn the tide in favor of the allies. When Tobel disappears leaving behind only a cryptic message, it's up to Holmes and Watson to crack the code and track down the missing inventor. The Secret Weapon is notable for the first appearance of Dennis Hoey as Inspector Lestrad, a Scotland Yard detective who will would appear in several subsequent films