Today, the figure of Sherlock Holmes towers over detective fiction like a colossus--but it was not always so. Edgar Allan Poe's Dupin, the hero of "The Murders in the Rue Morgue," anticipated Holmes' deductive reasoning by more than forty years. In A Study in Scarlet, the first of Holmes' adventures, Doyle acknowledged his debt to Poe--and to mile Gaboriau, whose thief-turned-detective Monsieur Lecoq debuted in France twenty years earlier.

If Rue Morgue was the first true detective story in English, the title of the first full-length detective novel is more hotly contested. Among the possibilities are two books by Wilkie Collins--The Woman in White (1859) and The Moonstone (1868)--Mary Elizabeth Braddon's The Trail of the Serpent (1861) or Aurora Floyd (1862), and The Notting Hill Mystery (1862-3) by the pseudonymous "Charles Felix."

As the early years of detective fiction gave way to two separate golden ages--hard-boiled tales in America and intricately-plotted "cozy" murders in Britain--and these new sub-genres went their own ways, their detectives still required the intelligence and clear-sightedness that characterized the earliest works of detective fiction: the trademarks of Sherlock Holmes, and of all the detectives featured in these pages.