The Valley of Fear is the fourth and final Sherlock Holmes vel. It is based on the real exploits of the Molly Maguires and Pinkerton agent James McParland. Sherlock Holmes and Dr. Watson receive a letter from an informant. The letter is written in a numeric code. They decode the letter which warns that John Douglas of Birlstone House is about to be murdered. Sir Arthur Ignatius Conan Doyle was a Scottish physician and writer, best kwn 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, n-fiction and historical vels.