The Sign of the Four -  is a novel by Arthur Conan Doyle, a British writer and medical doctor. He created the characters of Sherlock Holmes and Dr. Watson. The Sherlock Holmes stories are considered milestones in the field of crime fiction.<br/>The Sign of the Four is the second novel featuring Sherlock Holmes written by Sir Arthur Conan Doyle. Set in 1888, The Sign of the Four has a complex plot involving service in India, the Indian Rebellion of 1857, a stolen treasure, and a secret pact among four convicts ("the Four" of the title) and two corrupt prison guards. It presents Holmes's drug habit and humanizes him in a way that had not been done in the preceding novel. It also introduces Dr. Watson's future wife, Mary Morstan.