The Valley of Fear is the fourth and final Sherlock Holmes novel by British writer Arthur Conan Doyle. Loosely based on the Molly Maguires and Pinkerton agent James McParland. The story was first published in the Strand Magazine between September 1914 and May 1915. The first book edition was copyrighted in 1914, and it was first published by George H. Doran Company in New York on 27 February 1915 and illustrated by Arthur I. Keller.
Sherlock Holmes receives a cipher message from Fred Porlock, a pseudonymous agent of Professor Moriarty. Holmes deciphers the message as a warning of a nefarious plot against a man surnamed Douglas, a country gentleman residing at Birlstone House. Some minutes later, Inspector MacDonald arrives at 221B Baker Street with news that Douglas was murdered the night before. MacDonald, Holmes, and Watson travel to Birlstone House to investigate.