When you arrive in Dartmoor, ask the policeman by the Tavistock train station SELDEN, and he'll tell you about the Notting Hill Murderer Harry Selden, who escaped and is hiding out on the moors. He'll ask if you're interested in arresting him. Ask the policeman ARREST and he'll give you a pair of manacles. Ask Dr. Mortimer (who is next to Dr. Watson in town, during the day only) SELDEN, and he'll tell you that Mrs. Barrymore, the stewardess at Baskerville Hall's maiden name was Selden. Ask Mrs. Barrymore SELDEN and she'll tell you about her brother, the murderer, who came to her for help and who is hiding out on the moors. She'll give you a bowl of potato soup. With this in your inventory, go to the ruined sheepfold, EESSSE of Baskerville Hall. Harry Selden will take the soup out of your inventory, and ask what you want. Give him the manacles the policeman gave you, and he'll attack you. Beat him til he's dying and he'll surrender, then give him the manacles and you'll receive XP and the whois.