In 1887, Arthur Conan Doyle introduced Sherlock Holmes in A Study in Scarlet. When we first meet Holmes, he’s a young eccentric who needs a roommate. Dr. John Watson, an injured veteran of Afghanistan, moves in with Holmes and begins to learn what a unique fellow his companion is.
In A Study in Scarlet, Holmes emphasizes his role as a consulting detective. The job, as described by Holmes, involved helping other detectives who have gotten stuck in their efforts to solve a case. This emphasis on being a consultant disappears in later stories as Holmes often has clients of his own.
Holmes took on a wide variety of complex mysteries, told in short stories and novels. He captured the interests of readers, but Doyle became worried Holmes was preventing him from moving in more serious literary directions, so in 1893, Doyle killed off Holmes in a fight with his newly introduced archenemy, Professor Moriarity.
Doyle only left his audience demanding more. Doyle wanted to cash in by creating a stage version of Holmes. After a long process, he found actor/playwright William Gillette who adapted Holmes to the stage. Gillette added greater definition to the Holmes character in the public mind. The phrase, "Elementary, my dear Watson." had its genesis in Gillete's play.
Gillete traveled throughout the world, playing the role of Holmes on stage for forty years, and later became the first actor to play Holmes on the radio. These efforts increased the public demand for more Sherlock Holmes stories. Doyle tried to respond to this demand in ways that wouldn't commit him to further projects. He released Hound of the Baskervilles as a novel that was set before Holmes' death. Doyle finally relented and brought Holmes back from the dead for The Return of Sherlock Holmes. That collection of short stories ended with Watson stating Holmes had forbidden him from writing down any additional stories.