Sherlock Holmes is the most famous fictional detective in history, with a popularity that has never waned since catching the imagination of his late-Victorian readership. This Companion explores Holmes' popularity and his complex relationship to the late-Victorian and modernist periods; on one hand bearing the imprint of a range of Victorian anxieties and preoccupations, while on the other shaping popular conceptions of criminality, deviance, and the powers of the detective. This collection explores these questions in three parts. 'Contexts' explores late-Victorian culture, from the emergence of detective fiction to ideas of evolution, gender, and Englishness. 'Case Studies' reads selected Holmes adventures in the context of empire, visual culture, and the gothic. Finally, 'Holmesian Afterlives' investigates the relationship between Holmes and literary theory, film and theatre adaptations, new Holmesian novels, and the fandom that now surrounds him.