In 1888 Mary Morstan comes to Holmes with two puzzles. The first the disappearance ten years earlier of her father Captain Arthur Morstan in 1878. The second puzzle is that she has received a pearl in the mail every year for the last six years. Accompanying the last pearl was a letter remarking that she had been wronged and requesting a meeting. Originally published in 1890 'The Sign of Four' is the second novel featuring Sherlock Holmes written by Sir Arthur Conan Doyle. Includes article on the history of the novel.