A Study in Scarlet is an 1887 detective novel by British author Arthur Conan Doyle. Written in 1886, the story marks the first appearance of Sherlock Holmes and Dr. Watson, who would become two of the most famous characters in popular fiction. The book's title derives from a speech given by Holmes, an amateur detective, to his friend and chronicler Watson on the nature of his work, in which he describes the story's murder investigation as his "study in scarlet" "There's the scarlet thread of murder running through the colourless skein of life, and our duty is to unravel it, and isolate it, and expose every inch of it.A Study in Scarlet is one of only four full-length novels in the original canon. The novel was followed by The Sign of the Four, published in 1890. A Study in Scarlet was the first work of detective fiction to incorporate the magnifying glass as an investigative tool.