The Sign of Four -  Arthur Conan Doyle A strange letter and a fortune in jewels and pearls lead Holmes and Watson on a merry chase. In this story, we meet the lovely Miss Mary Morstan and are also introduced to Sherlock's cocaine habit. I think Sherlock must be bipolar and so does Dr. Watson. He gets really annoyed with Sherlock indulging in his drugs of choice. Anyhow, this was fun, the who dunnit and the history behind the treasure was also very interesting.