The Valley of Fear

Sherlock Holmes receives a coded message from Fred Porlock, an informant tied to Professor Moriarty. It warns that a man named Douglas is in danger. Before Holmes can act on it, Inspector MacDonald of Scotland Yard arrives with worse news: John Douglas is dead.

The killing happened in rural England, inside the moat of Birlstone House, an old manor. Holmes and Watson head there and join the local detective, White Mason. The physical clues refuse to fit together neatly, and the case resists the obvious reading.

The book falls into two parts. The first, The Tragedy of Birlstone, is a puzzle set in a country house, in the closed-circle tradition. The second, The Scowrers, shifts to a coal-mining valley in America and a secret society whose history accounts for events in England.

Conan Doyle wrote four Sherlock Holmes novels, and this one is the last. The Strand Magazine ran it in installments starting in 1914, and the book edition followed in 1915. Moriarty hangs over the whole story without ever appearing in person, and the long flashback carries the answer to the Birlstone murder.