Army surgeon invalided home from Afghanistan who becomes Sherlock Holmes's companion, lodger, and chronicler. Steady, decent, and possessed of considerable courage, he serves as both the practical counterweight to Holmes's eccentricity and the reader's point of entry into a world that would otherwise be entirely alien. Narrator of the overwhelming majority of the canonical stories.

The world's only consulting detective, operating from 221B Baker Street, London. Possessed of extraordinary powers of observation and deductive reasoning, he applies a rigorous scientific method to criminal investigation while remaining largely indifferent to conventional social expectations. Capable of brilliant warmth and profound coldness in equal measure, his partnership with Dr Watson is the central relationship of the canon.

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.

A country doctor and man of science who brings the Baskerville case to Holmes, having witnessed the death of Sir Charles Baskerville and found evidence that defies rational explanation. Scholarly, nervous, and genuinely frightened, he is the reader's introduction to the Dartmoor world of The Hound of the Baskervilles and one of its more sympathetically drawn supporting figures.

Scotland Yard's most prominent inspector in the canon and Holmes's most frequent professional contact within the official police. Tenacious and not without competence, but habitually out of his depth on the cases that matter most, he represents the institutional approach to detection that Holmes consistently outpaces. His relationship with Holmes evolves from grudging tolerance to genuine respect across the canon.

The Canadian-raised heir to the Baskerville estate on Dartmoor, drawn back to England by the death of his uncle Sir Charles and the apparent threat of a family curse. Direct, practical, and considerably braver than his situation might warrant, he is the client and central concern of The Hound of the Baskervilles - the most celebrated case in the canon.