The Valley of Fear is the fourth and final Sherlock Holmes novel by Sir Arthur Conan Doyle. It is 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.
Unlike many of the other Holmes novel which are mostly linear entertainments, Doyle crafted The Valley of Fear " two parts and a coda and carefully stage managed the elements of fear and terror."
The novel has a number of major themes, including "problems of "ethical ambiguity" and attempted to comment seriously on terrorist activity [as profiled by] American labor struggles" Critics have shown how the American labor struggles, deal with similar issues in the contemporary political situation in Ireland.