When Mr. Oldcastle wins some money it goes straight to his head, making him think some very strange thoughts - like trading Gumdrop in for a vintage Rolls-Royce or a sleek new Jaguar. But Gumdrop plays a few tricks that help Mr. Oldcastle change his mind.
Mr Oldcastle has taken Gumdrop on holiday to Scotland. Their final destination is the famous Loch Ness where they hope to see the legendary monster. Several other people have had the same idea! But will anyone see the real monster?
Mr Oldcastle and his grandson Dan set off for Mildew Manor - the sort of place you would expect a ghost to appear. The first one they meet is revealed as Marmaduke Ricketty-Cobwebb, owner of the Manor, dressed up to scare visitors. But then Gumdrop finds a real ghost - a Rolls Royce Silver Ghost!