"The Valley of Fear" by Arthur Conan Doyle is a novel first published in 1915. In this fourth Sherlock Holmes mystery, the detective receives a coded warning about a plot against a country gentleman named Douglas. When Holmes arrives to investigate, he discovers Douglas has been murdered at his moated manor house. The case leads to dark secrets involving American coal miners, a corrupt trade union, and the dangerous Professor Moriarty. Holmes must unravel a mystery that spans two continents and threatens more lives.