When Dr. Mortimer visits Sherlock Holmes and Dr. Watson in their rooms in Baker Street, he brings a centuries-old account of the death of the debauched and ruthless Sir Hugo Baskerville, allegedly killed by a diabolical hound. Dr. Mortimer's friend and neighbor, Sir Charles Baskerville, recently died under circumstances that suggest that this ancient curse on the family persists. Mortimer is concerned for the safety of the Canadian heir, Sir Henry Baskerville, who is to arrive in London the next day en route to the Baskerville estate in Devon. Mortimer also describes the few neighbors on the moor, a group consisting of Mr. Stapleton, Miss Stapleton, Mr. Frankland, and Mr. Frankland's daughter.