The Sign of the Four

The Sign of Four is the second novel featuring Sherlock Holmes written by Sir Arthur Conan Doyle. Doyle wrote four novels and 56 stories starring the fictional detective. The story is set in 1888. The Sign of 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 the detective's drug habit and humanizes him in a way that had not been done in the preceding novel, A Study in Scarlet (1887). It also introduces Doctor Watson's future wife, Mary Morstan. According to Mary, in December 1878, her father had telegraphed her upon his safe return from India and requested her to meet him at the Langham Hotel in London.