Dressed to Kill (1946 film)

Dressed to Kill, released in 1946, also known as Prelude to Murder working title and Sherlock Holmes and the Secret Code in the United Kingdom, is the last of fourteen films starring Basil Rathbone as Sherlock Holmes and Nigel Bruce as Doctor Watson.

A criminal gangs brains belong to a darkly beautiful, ruthless woman, who is also a consummate actress, as Sherlock Holmes learns. She disguises herself as a charwoman and speaking Cockney, she talks to both Holmes and Watson, whom she pretends not to recognize, and leaves with a music box right under their noses. Holmes must recover the last music box to crack the secret code contained in the tune before it is too late.

Source: Wikipedia