The Sign of the Four is the second novel featuring Sherlock Holmes. It has a complex plot involving service in East India Company the Indian Rebellion of 1857 a stolen treasure and a secret pact among four convicts and two corrupt prison guards. It also introduces Doctor Watsons future wife Mary Morstan. Sir Arthur Ignatius Conan Doyle was a Scottish physician and writer best known for his Sherlock Holmes detective stories and for the adventures of Professor Challenger. He was a prolific writer whose works include science fiction stories plays romances poetry non-fiction and historical novels.