Sir Charles Baskerville, a baronet, is found lying dead among yew trees in the grounds of his country house, Baskerville Hall. The cause of death is ascribed to a heart attack. Fearing for the safety of Sir Charles's nephew and only known heir, Henry Baskerville—who was coming to London from Canada to claim his inheritance—Dr James Mortimer travels from Devon to London, and appeals for help to Sherlock Holmes.
Mortimer explains to Holmes and Watson that the Baskerville family is said to be afflicted by a curse. He reads a description of the origin of the curse, as written down by a descendant of one Hugo Baskerville, who had lived two centuries earlier. According to this old account, Hugo Baskerville became infatuated with a yeoman's daughter, kidnapped her, and imprisoned her in his bedchamber. She escaped while he was talking with his friends. A drunken and furious Baskerville offered to give his soul to the Powers of Evil if he could only overtake her. This Baskerville, aided by his friends and hounds, rode after the girl onto the desolate moor. Some time later, Baskerville and his victim were both found dead. She had died from fear and fatigue, while a giant spectral hound stood over Baskerville's body. With his friends watching, the hound devoured Baskerville's throat and vanished into the night.
Mortimer reports that before his death, Sir Charles Baskerville had become fearful of the legendary curse and its hellhound. Furthermore, he has deduced that Sir Charles had been waiting for someone at the time of his death. Sir Charles's face was contorted in death into a ghastly expression, while his footprints suggested that he was desperately running from something. It was known that the elderly Sir Charles's heart was not strong, and also that he planned to go to London the next day. Mortimer also reveals that he had himself observed the footprints of a "gigantic hound" near Sir Charles's body, a fact he had not revealed at the inquest.