The Valley of Fear is the fourth and final Sherlock Holmes novel by British writer Arthur Conan Doyle.

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.

[2] 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 one Douglas, a country gentleman residing at Birlstone House.

Barker believes a secret society of men pursued Douglas, and that he retreated to rural England out of fear for his life.

Working for the Pinkertons, Edwards had travelled to Vermissa Valley to infiltrate a corrupt coal miner's trade union, secretly a cover for a murderous gang.

The Valley of Fear was first published in book form by George H. Doran Company in New York on 27 February 1915, after the serialisation was completed in the United States but before it had finished in the Strand.

The novel has a number of major themes, including "problems of ethical ambiguity", and attempts to comment seriously on terrorist activity as profiled by American union struggles.

Critics have shown how the American union struggles deal with similar issues in the contemporary political situation in Ireland.