Sherlock Holmes and the Secret Weapon (1942 Roy William Neill)

Source is 'The Dancing Men' updated to incorporate Swiss (?) bomb expert professor at centre of story. He's played by William Post Jr as 'to get a foreign accent, just speak really deliberately'. His wife is Kaaren Verne (from King's Row) who gets to say about three lines. Rathbone and Bruce are pitched against Lionel Atwill's Moriarty.

Love the design of the 'clue' itself

Holmes recovers from having five pints of blood drained in about five seconds, Watson falls asleep on the job. Holmes' disguises include a Swiss professor and a tough mariner of indeterminate origin.

The final plea to 'Buy War Bonds' should have been amended - 'Or we'll make more films like this one'.