Dressed to Kill (1946)

Sherlock Holmes is intrigued when Dr. Watson's friend, Julian 'Stinky' Emery, visits and tells them of a strange robbery at his flat the previous night. Stinky is an avid collector of music boxes and has several quite expensive pieces in his vast collection. The previous night, someone broke into his flat and knocked him unconscious when he tried to intervene.

All they took however was a simple wooden music box he had bought at auction that day for a mere £2. The box was one of three available for sale and as Holmes and Watson begin to trace the other purchasers, it becomes apparent that someone will stop at nothing, including murder, to retrieve all three. When Holmes learns the identity of the music box maker, he is convinced it contains directions to the retrieval of something very valuable that the government has kept from the public.