A consulting detective and his companion are drawn into a rural mystery when a family believes a hereditary curse in the form of a monstrous hound threatens the heir after a strange death on a bleak moor. The companion chronicles an investigation that combines local legend, forensic observation, and undercover work: one man remains in town while the detective stages covert inquiries. Gothic atmosphere, dangerous bogs, and anonymous warnings heighten tension until careful deduction reveals a human plot using a fierce dog to mask murder for inheritance motives; justice is achieved and the superstition is dispelled.