<p>Holmes decodes a warning from Porlock, an informant against arch-criminal Moriarty, for "Douglas" resident five years at "Birlstone".<br><br>Scotland Yard's MacDonald asks them to investigate a corpse with the same look and circle-in-triangle brand on the forearm as Birlstone owner Douglas. The head was blown off by an American-style sawed-off shotgun. Apparently, an intruder dropped a card with VV341, and left across a shallow moat. Watson ob...