On holiday in Saltbottle, Grandfather and Roo discover the Unsinkable, the boat which took them to the North Pole in the first book, lying in a sadly dilapidated state and up for sale. At the auction, the short-sighted auctioneer accidentally sellsthe boat to Roo - sold to the old lady in the brown fur coat Now they have to find the money and the Captain suggests a fishing trip to the Great Cod Banks in the Forgotten Sea. Off they go, but the trip...