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Stories from the author's list of «12 favourite Sherlock Holmes stories».

Holmes and Watson go on holiday to Cornwall. A few days later, they are visited by Mr Mortimer Tregenis and Mr Ryndhay, who inform them that two of Mr Tregenis's brothers have gone mad and his sister has died. Brenda died with a horrified expression on her face. After a while, Mr Mortimer Tregenis himself died, just like his sister. Holmes explores the room and picks up a lamp that was on the table in the deceased's room. When it was lit, the killing effect was immediate, and Watson got Holmes out of the room in time. Holmes realises that Mortimer Tregenis used a poisonous powder to kill his brothers and sister, but who killed him?