How is the mystery solved at the end of The Hound of the Baskervilles by Arthur Conan Doyle?

In Sir Arthur Conan Doyle's mystery novel The Hound of the Baskervilles, Mr. Sherlock Holmes and Dr. John Watson have been asked to look into the death of the late Sir Charles Baskerville. The facts of Sir Charles' death appear to be quite plain-- he died of a fright-induced heart attack when confronted by a demon hound. At least, that is the version of the story most people are prepared to suspect. Even Dr. Mortimer,...

In Sir Arthur Conan Doyle's mystery novel The Hound of the Baskervilles, Mr. Sherlock Holmes and Dr. John Watson have been asked to look into the death of the late Sir Charles Baskerville. The facts of Sir Charles' death appear to be quite plain-- he died of a fright-induced heart attack when confronted by a demon hound. At least, that is the version of the story most people are prepared to suspect. Even Dr. Mortimer, who brings this case to Holmes and Watson, feels that the only possible explanation of Sir Charles' death is supernatural. Holmes does not think so and begins to develop suspicions otherwise. In order to better investigate and try to prevent the death of Sir Henry--the inheritor of Baskerville Hall-- Holmes and Watson make a visit to the Estate. Watson stays behind while Holmes returns to London to carry on other business, with the request that Watson send regular reports to him of any happenings on the Estate.

I think that Mr. Holmes has solved the case by the time he heads back to London, leaving Dr. Watson in Devonshire. It's not like him to abandon the scene of a crime without having solved his case. This is one of those particular instances where Holmes has solved the case quite early on but needs to let events play out in order to prove himself to be right to others and to appropriately catch the criminal in the act. Though Holmes has already solved the case, he allows the events to play out and steps in at just the right moment.

Holmes tells Sir Henry that he ought to go about his business as usual, expecting that this will draw out the spectral hound and whoever is in charge of it. After a visit at the Stapleton house, Sir Henry is walking home alone in the dark. Holmes, Watson, and their fellow Inspector Lestrade are hiding on the moor to watch over Sir Henry when suddenly-- there it is! A great, glowing, apparently spectral dog runs up and attacks Henry but is shot dead by Holmes. When they investigate the dog's body, they find that it is simply Stapleton's very large dog covered with phosphorous powder. As it turns out, Stapleton was an estranged cousin of Sir Henry and was trying to frighten (or flat-out kill) all of those in line ahead of him to inherit the estate. Holmes had figured this out long prior but it was necessary to let events play out and catch Stapleton red-handed.