Arthur Conan Doyle was a Scottish writer and physician best known for his stories featuring the legendary detective Sherlock Holmes. Conan Doyle was a prolific author and his innovative mysteries make him one of the most widely read authors in history. Conan Doyle also wrote The Lost World, which was one of the earliest and most influential works in the lost world genre of fiction. The Sign of the Four, published in 1890, is a novel that begins with a beautiful young woman asking Sherlock and Watson to accompany her as she meets with a mysterious benefactor. The Valley of Fear, published in 1915, is the final Sherlock Holmes novel. The book begins with Sherlock receiving a message from an agent of Professor Moriarty.