What is the name of the criminal organization in 'The Valley of Fear'?

The criminal organization in The Valley of Fear is called the Scowrers.

The Scowrers are the murderous gang at the centre of the novel’s American backstory. They operate in Vermissa Valley, a coal-mining region where intimidation, violence, and corruption have made ordinary life dangerous. John Douglas, whose real identity is Birdy Edwards, infiltrates the organization while working undercover for the Pinkerton detective agency.

Edwards enters Vermissa under the name Jack McMurdo and gradually learns how deeply the Scowrers control the local community. Their crimes include murder and coercion, and their influence extends into labour disputes and local institutions. The gang’s actions eventually lead to a major investigation and the collapse of its power, but surviving members continue to threaten Edwards years later.

The Valley of Fear was Arthur Conan Doyle’s fourth and final Sherlock Holmes novel. First serialized in The Strand Magazine from September 1914 to May 1915, it is divided into “The Tragedy of Birlstone” and “The Scowrers.” The gang’s fictional history was loosely inspired by accounts of the Molly Maguires and the real Pinkerton agent James McParland. The Brotherhood, Syndicate, and Red Circle are plausible-sounding distractors, but none is the organization’s name in the novel.