The stories have been in print continuously since the time the first one, A Study in Scarlet, was published in 1887. In addition Holmes has been the leading character in hundreds of plays, films, and television shows. He made his debut in films even before Conan Doyle had finished writing the stories. Long before Basil Rath-bone and Nigel Bruce created their memorable roles of Holmes and Watson in films of the late 1930s and the 1940s, the celebrated sleuth had already been played by a host of actors on stage and screen. The stories continue to be filmed today. You have probably seen one of the excellent Granada Television episodes with Jeremy Brett, which may well be the reason you are reading this book.

Sherlock Holmes has such a strong hold on the popular imagination that he is no longer moored to the books in which he first appeared. Not satisfied by the fifty-six short stories and four novellas of the Holmes canon, writers first adopted the character by completing cases Dr. Watson had mentioned only in passing. Soon they constructed new episodes for the master detective. Film directors followed suit. Though many films have been scrupulously true to the plots of the stories, some have created their own plots. Such films include Young Sherlock Holmes (1985), which invented a childhood for the detective. In it Holmes and Watson meet as teenagers at a boarding school where Professor Moriarty, Holmes’s great nemesis in the books, is an encouraging teacher. It also introduces a love interest for Holmes, a young girl whose death at the hands of Moriarty, who turns into a deadly foe, explains why Holmes was never the marrying kind. The Seven-Per-Cent Solution (1976) sends Holmes to Vienna to meet Sigmund Freud, who traces Holmes’s obsession with Moriarty to a repressed memory of his mother in the arms of the professor. In perhaps the boldest reimagining of the stories, and certainly the most amusing, Without a Clue (1988) reveals that Watson was the real detective genius and that Holmes was his fictional creation; when the public clamored to meet Holmes, Watson hired a dim-witted actor to play the role.

So powerful is the Holmes persona that even tangential connections attract viewers. In 2000 and 2002 the Public Broadcasting System aired a joint British-American series of mysteries that featured Conan Doyle and his teacher, Dr. Joseph Bell, on whom Holmes was partly modeled, as characters solving crimes in the manner of Holmes and Watson. Called Murder Rooms: The Dark Beginnings of Sherlock Holmes, the episodes weave incidents from Conan Doyle’s life into fictional plots that foreshadow the great stories to come. But clearly the draw for the series is the name of the immortal detective.

So how did this all begin? While the springs of creation are always ultimately mysterious, they are never entirely hidden. As with every mystery, there are clues. The most promising sources, as with most writers, are biographical.

Arthur Conan Doyle was born in Edinburgh, Scotland, in 1859. He was a healthy, athletic lad, who appeared to have a happy childhood. He grew up in a middle-class family with a keen sense of its place in society and history. His family was originally from Ireland. His grandfather, John Doyle, like many gifted Irishmen, had moved to London, where he made his name as a political cartoonist. His four sons all became artists of one sort or another. Conan Doyle’s Uncle Richard knew Dickens; a warm letter from the great novelist survives in the family archives. Richard was also a friend of William Thackeray, whose works he had illustrated. The author of Vanity Fair once bounced young Arthur on his knee while paying a visit to Conan Doyle’s father, Charles, who worked as a young architect in the Government Office of Works.