Some weeks later, Watson asks Holmes about the Baskerville case. Holmes reveals that although believed to have died unmarried, Sir Charles Baskerville's youngest brother Rodger had married and had one child, also named Rodger. His son had married a local beauty, Beryl Garcia. After embezzling public money in Costa Rica, he took the name Vandeleur and fled to England with her, where he used the money to fund a Yorkshire school. Unfortunately for him, the tutor he had hired died of Tuberculosis, and after an epidemic of the disease killed three students the school itself failed. Now using the name Stapleton, Rodger/Vandeleur fled with his wife to Dartmoor. He apparently supported himself by burglary.
Having learned the story of the hound, he resolved to kill off the remaining Baskervilles so that he could come into the inheritance as the last of the line. He had no interest in the estate and simply wanted the money. He bought the hound and hid it in the old tin mine in the middle of the Mire.
On the night of his death, Sir Charles had been waiting for Laura Lyons. The cigar ash at the scene ("the ash had twice dropped from his cigar") showed he had waited for some time. Instead he met the hound that had been trained by Stapleton and covered with phosphorus to give it an unearthly appearance. Sir Charles ran for his life, but then had the fatal heart attack which killed him.
Stapleton followed Sir Henry in London, and also stole his new boot but later returned it, since it had not been worn and thus lacked Sir Henry's scent. The hound pursued Selden to his death in a fall because he was wearing Sir Henry's old clothes and thus had his scent on him.
On the night the hound attacked Sir Henry, Stapleton's wife had refused to have any further part in Stapleton's plot, but her abusive husband beat her and tied her to a pole to prevent her from warning him.
In Holmes' words: "..he [Stapleton] has for years been a desperate and dangerous man.." It was his consuming interest in entomology that allowed Holmes to identify him as the same man as the former schoolmaster Vandeleur, after whom was named a certain moth that he had been the first to describe in his Yorkshire days.