Samuel Clemens, the most famous American author in London, and better known as Mark Twain, has had the notes for his memoirs mysteriously stolen from the illustrious Langham Hotel. Clemens, an admirer of Sherlock Holmes, approaches the famous detective for assistance. Holmes and Watson set out to track down the thief among a myriad of guests staying at the famous hotel. But all of the hotel guests have alibis. Is one of the hotel guests hiding something? Or did the burglar come from further afield? Suspects abound, yet another pressing question arises for Dr. Watson. Will one of them, a woman from his past, steal his heart?