Craig and Linda's parents have taken them to Canada this summer -- far away from "that wicked monster Nessie." But there's a secret passageway between Loch Ness and Lake Memphrémagog in Quebec. The passageway is part of a crumbling maze. Nessie's daughter, the Princess Sheona, has become trapped.Craig and Linda pay their last visit to Nessie's Grotto, and turn its care over to frightened 7-year-old Angus and his sister Haining, who is going to be a giant when she grows up.