Dressed To Kill (1946)

A convicted thief in Dartmoor prison (played by an uncredited Cyril Delevanti) hides the location of the stolen Bank of England printing plates inside three music boxes (each one plays a subtly different version of "The Swagman"). The boxes are sold at a local auction house. However, a criminal gang, the brains behind which belong to a darkly beautiful, ruthless woman, who is also a "consummate actress" as Holmes learns,and constantly wearing fur, when she, disguised as a charwoman and speaking Cockney, talks down to both Holmes and Watson, whom she pretends not to recognize, and leaves with a music box right under their noses. She has some muscle behind her but pers to use her brains. Holmes tries to recover the last music box to crack the secret code contained in the tune before it is too late.

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