The Sign of the Four - Arthur Conan Doyle

A stolen treasure, a secret pact among four convicts, and two corrupt prison guards. The Sign of the Four also presents the detective's drug habit and humanises him in a way that had not been done in the preceding novel, A Study in Scarlet. It also introduces Doctor Watson's future wife, Mary Morstan.

Sir Arthur Conan Doyle, an Edinburgh born physician and writer most famous for his stories about the detective Sherlock Holmes, considered a milestone in the field of crime fiction.  A prolific writer whose other works include science fiction stories, plays, romances, poetry, non-fiction, and historical novels. After graduating from Edinburgh University he first worked as a surgeon on a wailing boat and later settled in Portsmouth on the English south coast dividing his time between medicine and writing.