Alan Breck Stewart is the archetypal "dashing rogue." He is an excellent swordsman, marksman, and guide; he can find his way through the Scottish highlands while avoiding enemy soldiers hunting for him. However, like many such rogues, he is also a braggart, commenting on his skills to anyone who will listen. He is quick to take offense, but also quick to forgive.
He is also fiercely loyal to his clan, the Stewarts, and his country—the Highlands of Scotland. He defines himself by his clan and his Catholic faith. He is a Jacobite, and believes that the Scottish Stuarts should are the true kings of England.
Unlike David, Alan does not change significantly in the course of Kidnapped. His primary role is to serve as a kind of guide to David, both through the wilds of Scotland and through the trials of becoming a man. He teaches David how to survive in the wilderness, how to survive a battle, and he also shows David some of the ins and outs of politics, particularly clan politics. David, for his part, gains Alan's respect, though David is a Whig and a Protestant.
Alan Breck is the most interesting character in Kidnapped, and the one who most contributes to its adventurous nature. From his first appearance, where he causes the battle of the Round-House, to the last escape across the river in Queensferry, Alan remains an entertaining and essential aspect of the book.