Book excerpt: When Mary Russell is summoned by her partner and husband Sherlock Holmes to the scene of his most celebrated case, that of the Hound of the Baskervilles, there is more to the matter than a phantom hound. Sightings of a spectral coach carrying a long-dead noblewoman over the moonlit moor have heralded a corpse surrounded by oversized paw prints. As Russell and Holmes anticipate, a rational explanation lies beneath the supernatural events--but one far darker than they ever imagined. Martin's Press.