How did Holmes know that Stapleton was the criminal in Hound of the Baskervilles?Please answer me hurry! Thanks!
Sherlock Holmes initially began to suspect that Stapleton was behind the criminal dealings concerning the Baskerville estate when he closely examined the cryptic warning note received by Sir Henry. While making a close inspection for the water-mark, Holmes held the paper "within a few inches of (his)eyes", and in doing so, became conscious of "a faint smell of the scent known as white jessamine". The scent of perfume indicated the presence of a lady, which turned his attention to the Stapletons, since Beryl Stapleton was one of the few women living in the vicinity on the moor and the only one so far closely related to the case.
Upon looking into Stapleton's history, Holmes discovered a number of startling facts. First of all, although Stapleton had presented Beryl as his sister, Holmes discovered that she was in fact his wife. The fact that Stapleton was lying about this particular detail indicated some sort of sinister intent. The big breakthrough for Holmes, however, was in uncovering Stapleton's true identity and his familial connection to the Baskervilles. After noting an uncanny resemblance between Stapleton and a portrait of one of the Baskerville ancestors, Holmes inquired further and found that Stapleton was "the son of...Rodger Baskerville, the younger brother of Sir Charles, who fled with a sinister reputation to South America, where he was said to have died unmarried...(Rodger) did, as a matter of fact, marry, and had one child", the man who presently was calling himself Stapleton.
As the son of Rodger Baskerville, there were "only two lives interven(ing) between (Stapleton) and a valuable estate". With this information, Holmes knew that Stapleton, who was already acting with duplicity, had a strong motive for wanting Sir Charles and Sir Henry dead (Chapter 15).