When Dee is told that there is a haunted castle close to the School Camp Site in the Highlands of Scotland she just has to go to investigate. And Trevor's school will be there too. But the pretty Sandy Griffiths, Dee's rival for Trevor is now going to Trevor's school and is coming too. But there are other mysteries besides the ghost. Why has the Castle and a cave to it got such strong doors? What about the second ghost that appears in the hills? And the silent motor boats on the loch? Are these all connected with the spate of robberies in Inverness? And how will Dee and Trevor escape from being tied up and gagged in that cave?