"The Valley of Fear" is a novel by Sir Arthur Conan Doyle, featuring his famous detective Sherlock Holmes. It was first published in serial form in 1914–1915 and then as a book in 1915. The novel is divided into two parts: the first part takes place in England and involves Holmes solving a murder mystery, while the second part, set in America, provides the backstory leading up to the murder. The story begins with Holmes and Dr. Watson receiving a mysterious cipher message warning of danger to a man named Douglas. They soon learn that Douglas has been murdered in his own home. As Holmes investigates the murder, he uncovers a complex web of intrigue involving secret societies, revenge, and betrayal. The second part of the novel is a flashback to events leading up to the murder, detailing the rise of a criminal organization known as the Scowrers in America and their conflict with a man named John Douglas, who had infiltrated their ranks under the alias of Birdy Edwards. "The Valley of Fear" is notable for its intricate plot, well-drawn characters, and the clever deductions of Sherlock Holmes. It's one of the four Sherlock Holmes novels written by Conan Doyle and remains a classic of detective fiction.