The primary antagonist of The Hound of the Baskervilles, presenting himself as a harmless naturalist and neighbour to the Baskerville estate while concealing both his true identity and his murderous intentions. His connection to the Baskerville family is itself a central solution spoiler. One of the most effectively constructed villains in the canon - his surface affability and genuine expertise as an entomologist make him a convincing presence before the revelation.