There are still some things I don't understand,' I said to Holmes. 'Tell me - who was Stapleton?Why did he want to kill Sir Henry?' 'It is simple, my dear Watson,' said Holmes. 'Remember Sir Charle has two brother. The youngest and brother, Roger, was a bad man. He got into triuble over money and went to South America. He died in Venezuela. He did not marry, so no one knew he had a son.'
And this son called himself Stapleton?
Yes, and the son was both bad and clever. He wanted the Baskerville money. There were only two Baskervilles left alive - Sir Charles and Sir Henry. If they died, Baskerville Hall would belong to Stapleton.
What about his wife? Why did Stapleton say she was his sister?
‘At first Stapleton wanted her to marry Sir Charles or Sir Henry. That was a way of getting the money.’ What an evil man!' I said. "But she did not want to help Stapleton. She tried to warn both of them, didn't she?
Yes, she tried to meet Sir Charles the night he died. But Stapleton found out. Stapleton waited for Sir Charles and frightened him to death with the black dog. Also, Mrs Stapleton sent the note to Sir Henry at Northumberland Hotel. Then Sir Henry fell in love with Mrs Stapleton was worried and angry. At last, Stapleton to tie her up to stop her had telling Sir Stapleton, so Stapleton was worried and angry. At last, Stapleton had to tir her up to stop her telling Sir Henry.