Frank Osbaldistone, the narrator, quarrels with his father and is sent to stay with an uncle, Sir Hildebrand Osbaldistone, in Northumberland. Frank falls in love with Diana Vernon, Sir Hildebrand's niece, whose father has been forced to go into hiding because of his Jacobite sympathies. Frank's cousin, Rashleigh, steals important documents vital to the honor and economic solvency of Frank's father, William, and Frank pursues Rashleigh to Scotland. Several times his path crosses the mysterious and powerful figure Robert Roy MacGregor, known as Rob Roy, an associate of Diana's uncle Sir Hildebrand. There is much confusion as the action shifts to the beautiful mountains and valleys around Loch Lomond. A British army detachment is ambushed and there is bloodshed. All Sir Hildebrand's sons but Rashleigh are killed in the Jacobite Rising, and Rashleigh too meets a bloody end. Following this, Frank inherits Sir Hildebrand's property and marries Diana.
