The Valley of Fear, Fourth of the Four Sherlock Holmes Novels

The four Sherlock Holmes novels are: A Study in Scarlet, Sign of the Four, The Hound of the Baskervilles, and The Valley of Fear. According to Wikipedia: "Sir Arthur Ignatius Conan Doyle, (22 May 1859 – 7 July 1930) was an author most noted for his stories about the detective Sherlock Holmes, which are generally considered a major innovation in the field of crime fiction, and for the adventures of Professor Challenger. He was a prolific writer whose other works include science fiction stories, historical novels, plays and romances, poetry, and non-fiction."