Detective Sherlock Holmes and Dr. John Watson join forces to investigate a mysterious murder at Buckingham Palace. It seems like an open-and-shut case as all signs point to Professor James Moriarty, the criminal mastermind and longtime nemesis of the crime-solving duo. When new twists and clues begin to emerge, the world's greatest sleuth and his trusted assistant must now use their legendary wits and ingenious methods to catch the killer as they only have four days before the queen becomes the next victim.

Tom Canty, the youngest child of a very poor family living in Offal Court in London, sees one day Edward Tudor, the Prince of Wales. Coming too close in his intense excitement, he is caught and nearly beaten by the royal guards. However, Edward stops them and invites Tom into his palace chamber. There, the two boys get to know one another and are fascinated by each other's lives. They have an uncanny resemblance to each other, so they decide to swap clothes "temporarily". But things turn out differently.