Dr. John Watson (Kingsley) has fooled the world. He's created a work of fiction in the figure of the crime-solving sleuth, Sherlock Holmes, when it is he himself who has set about solving crimes. With the public demanding to see the legendary Holmes in the flesh, and to keep the charade in play, Watson hires out-of-work actor Reginald Kincaid (Caine) to assume the role with very mixed, and very funny, results. The game's afoot with Watson and the unlikely Holmes hot on the trail of Professor Moriarty, the nefarious mastermind behind a plot that could topple the British Empire.