The Hound of the Baskervilles
Holmes reveals his deductive reasoning: the warning note had a woman's perfume scent; the theft of the shoes gave a clue that the dog was real; Stapleton, who was a spiritual and physical throwback to Hugo Baskerville  (Holmes noticed the resemblance to the family portraits); his real name was Rodger Baskerville Jr (his father was the youngest of the Baskerville brothers and had to flee England for Central America). After marring a local beauty Beryl Garcia, he had stolen public money and fled Central America to England in 1885 where he used the money to start a public school in Yorkshire. The tutor he had hired died of consumption and the school which Baskerville then tried to use to teach his pupils crime was forced to close after an epidemic killed three students. In 1887 He then fled to his ancestrial home in Devon with the remains of his fortune, his wife and his taste for Entomology; Holmes cannot prove it but he theorizes that Baskerville supported himself by burglaries and in the process committed a murder. When he found out that one life was between him and a valuable estate and that Sir Charles had both a weak heart and took the family legend seriously, he bought a large savage dog and hid it on the moor. He tricked Laura Lyons into writing the appointment note for Sir Charles and sent the dog, coated with phosphorous, after the old man who died of a heart attack. He tried the same trick on his cousin Henry twice-the first time however it was the convict wearing Henry clothing that fell victim. He had tied up his wife so she could not warn Sir Henry of the danger he was in. In Holmes words: Roger Baskerville aka Jack Stapleton has for years been a dangerous and desperate man and one of the few foes worthy of confronting Sherlock Holmes The others being Dr Grimesby Roylott and Professor Moriaty).