The Sign of Four: The Sign of Four is the second novel (A Study in Scarlet being the first) featuring Sherlock Holmes written by Sir Arthur Conan Doyle. The story is set between 1887 and 1888. Mary Morstan receives anonymous packages every year since the disappearance of her father. It is a conspiracy. The novel reveals British colonist activities in India in an objective way. It becomes a great success soon after release and wins the author fame and reputation.