In The Adventures of Sherlock Holmes, Professor James Moriarity (played by George Zucco) devises a plan to steal the crown jewels from the Tower of London. To draw Sherlock Holmes (Basil Rathbone) into the case, Moriarity enlists the help of a young gaucho flute player named Ramon (David Clyde) to murder a young woman. The murder is made to look like a suicide, but Holmes quickly realizes it was a staged killing.
As Holmes investigates the murder, he becomes aware of Moriarity's plot to steal the crown jewels. He discovers that Moriarity has a secret workshop where he's been constructing a replica set of the jewels, and that he's planning on using them to replace the real jewels with fakes.
With the help of his trusty companion Dr. Watson (Nigel Bruce), Holmes goes to the Tower of London to uncover the truth and stop Moriarity's plan. In a thrilling climax, Holmes and Moriarity engage in a tense cat-and-mouse game as they race through the tower's corridors and up the spiral staircase.
Ultimately, Holmes manages to foil Moriarity's plot and return the real crown jewels to their rightful place. The Adventures of Sherlock Holmes is a thrilling and suspenseful mystery that showcases Rathbone and Bruce's iconic performances as the famous detective duo.