By Arthur Conan Doyle.
After Sir Charles Baskerville is frightened to death, probably by some spectral hound that is part of the family’s history, his heir, Sir Henry, returns from Canada to claim the title, but is immediately dogged in London by someone who seems to be trying to scare him off by sending him a warning or following him about the city.
Through the agency of his friend, Dr. Mortimer, Sir Henry visits Holmes, who finds the case most interesting, and sends Dr. Watson to act as his agent in Devon while he remains behind to deal with a case which requires his utmost concentration.
Once at Baskerville Hall with Sir Henry, Watson meets the locals, including the Stapletons. He is a naturalist who collects butterflies; she is his sister, who issues a warning that Sir Henry should get out while the going it good.
Though Watson and Sir Henry are inclined the doubt the presence of some infernal canine, they hear the howl of the creature across the moor.
In addition to the hound, there is also a convict called Selden, hiding out on the moors, and aided and abetted by Sir Henry’s housekeeper (the man’s sister) and her husband, Barrymore. But before he can escape from England, the hound pursues him to his death.
There’s also another visitor on the moors who, Watson eventually discovers, is Sherlock Holmes himself, who has been observing everyone’s doings incognito so that he can investigate the case more effectively.
He uses Sri Henry as bait, but fails to take the possibility of dense fog into account, saving the man’s life just in time, and hunting down Stapleton, another possible heir to the Baskerville estate, until it becomes clear that the bog has swallowed another victim.
The dog was merely a large breed of mortal hound with its mouth painted with phosphorus (which would probably have killed it; or have poisoned it slowly).
Stapleton’s sister, to whom Sir Henry had taken rather a fancy, was actually the man’s wife (and also a victim of his when she refused to co-operate with him), and like any good Victorian gentleman, Sir Henry sails off with a male companion, Dr. Mortimer, to recover from his ordeal.
In the best style of the penny dreadful, there is a certain amount of waffle in The Hound of the Baskervilles, especially the long epilogue in which Holmes explains what Stapleton had been up to. The so-called hell hound is part of the trope, and all the awkward questions which would have arisen in any subsequent trials are conveniently swallowed by Dartmoor. There is also the usual hyperbole about how mysterious and complex the case was, and just when Watson thinks that his own powers of deduction have improved through his association with Holmes, he finds that he’s still mostly wrong and merely confirming the master detective’s own rightness.