The year is 1887, and all of England is gearing up for the celebration of Queen Victoria's Golden Jubilee, marking her 50th year as monarch. London, naturally, is especially frenzied. Reading the paper one morning, Sherlock Holmes seizes upon one seemingly unimportant notice: the Tower of London has been closed for "reasons of security." The great detective is unsurprised when, moments later, he is asked to investigate the theft of the Crown Jewels. The clues left behind, however, positively reek of a carefully laid trap; Sherlock decides that he must step aside and allow Dr. Watson to pursue the thief instead. But if the Jewels are not replaced within 48 hours, the British government will be forced to admit that their most prized possessions were stolen and suffer worldwide humiliation. The player fills the role of Watson, travelling around London in Hansom cabs while attempting to recover the Crown Jewels while encountering many characters from Doyle's stories such as Mrs. Hudson, Mycroft Holmes, and Wiggins of the Baker Street Irregulars. A series of riddles and clues lead Watson on a hunt for inscribed jewels hidden at several famous sites across the city, including Westminster Abbey, Madame Tussauds Wax Museum, London Bridge, and Big Ben. Eventually, the villain is revealed as Professor Moriarty, who captures both Watson and Holmes. With quick thinking and the help of some humble medical supplies, however, Watson manages to subdue Moriarty and return the Jewels to the Tower in time.