The Valley of Fear

The Valley of Fear is the fourth and final Sherlock Holmes novel. It is based on the real exploits of the Molly Maguires and Pinkerton agent James McParland.
Sherlock Holmes and Dr. Watson receive a letter from an informant. The letter is written in a numeric code. They decode the letter which warns that John Douglas of Birlstone House is about to be murdered.
Sir Arthur Ignatius Conan Doyle was a Scottish physician and writer, best known for his Sherlock Holmes detective stories and for the adventures of Professor Challenger. He was a prolific writer whose works include science fiction stories, plays, romances, poetry, non-fiction and historical novels.

Sir Arthur Ignatius Conan Doyle KStJ, DL (1859 - 1930) was a British writer and physician. He created the character Sherlock Holmes in 1887 for A Study in Scarlet, the first of four novels and fifty-six short stories about Holmes and Dr. Watson. The Sherlock Holmes stories are milestones in the field of crime fiction.Doyle was a prolific writer. In addition to the Holmes stories, his works include fantasy and science fiction stories about Professor Challenger, and humorous stories about the Napoleonic soldier Brigadier Gerard, as well as plays, romances, poetry, non-fiction, and historical novels. One of Doyle's early short stories, "J. Habakuk Jephson's Statement" (1884), helped to popularise the mystery of the brigantine Mary Celeste, found drifting at sea with no crew member aboard. (Source: Wikipedia)