King Arthur decides to invade Scotland when he discovers Princess Guinevere has been taken to Hadrian's castle. Unfortunately, the King's armies are sent in the wrong direction. So, despite an invasion force of only four, King Arthur lays siege to the castle. Merlin levitates them over the battlements but Guinevere is nowhere to be found. In the end, Lancelot and Martyn are trapped on an island by the Loch Ness monster and King Arthur searches the length and breadth of Scotland only to discover Guinevere has returned to her tower after a family visit with her Scottish relatives.