The year is 1888. Mary Morstan visits Sherlock Holmes and presents him with a startling new case. On seeing an anonymous advert in the newspaper in 1882 asking for her address, Mary responded and then received, also anonymously, a valuable pearl through the post each year for six years. After the sixth pearl, a letter arrives asking for a meeting. Could these events relate to the disappearance of her father ten years ago, or to the death of her father's only friend, Major Sholto, in 1882? Holmes takes up Mary's case and uncovers theft, corruption and death whilst interpreting the mysterious note 'The Sign of Four'. This Oxford Essential Texts edition of Conan Doyle's classic mystery comes with accessible and informative notes.