A Study in Scarlet is a classic detective novel by Sir Arthur Conan Doyle, marking the first appearance of the legendary Sherlock Holmes, one of the most famous fictional detectives in history. Written in 1886 and published in 1887, the novel’s title comes from Holmes’s description to Dr. Watson of their murder investigation as a "study in scarlet": "There’s the scarlet thread of murder running through the colourless skein of life." Out of 56 Sherlock Holmes stories, only four are full-length novels, with A Study in Scarlet being the first, followed by The Sign of Four in 1890. This novel is also notable for introducing the magnifying glass as a key investigative tool in fiction. Summary by Lami