Generally, one of the primarily traits of a story's protagonist is that he or she is dynamic. This means that their character develops over the course of the novel, usually becoming more experienced, more mature, and more capable. They overcome a number of problems they have never encountered before and are often very different people by the end of the story.

In Kidnapped, David can easily be recognized as a protagonist. At the beginning of the book, he is a naïve country boy, only seventeen years old. He is so inexperienced that he easily falls for his uncle's various traps; only blind luck saves him from falling to his death in the tower of the House of Shaws, and Captain Hoseason at Queensferry easily dupes him. But by the end of the book, David has gained much experience. He has come close to death twice, on the Covenant and in the house of the McLarens. He killed two men in the battle of the Round-House, he has witnessed the murder of Colin Campbell of Glenure, and he has debated politics with Alan, a Jacobite. David has crossed the Scottish highlands, much of it alone. When he returns home, he is so much wiser that he is able to play a trick on his own uncle and secure his fortune. He has gone through several trials-by-fire, and few would argue that he has not "become a man" by the end of the novel. Furthermore, he comes into a great inheritance and his life is completely changed by the end of the story. There is little doubt that David is a protagonist.

Alan Breck Stewart certainly has a large role in Kidnapped. He is present for nearly two-thirds of the story, and he is an essential part of David's development. However, at the end of the story, there seems little evidence that Alan has been changed at all. He has developed a friendship with David, and it could be argued that Alan might think more kindly of Whigs, but these are small changes. Alan's understanding of the world has not changed significantly at the end of the novel. While he is certainly one of the most important characters of the book, he is not a protagonist.

In Kidnapped, David and Alan often define themselves by their political associations. David is a Whig, which means he is loyal to the current English government and the king, King George. Alan is a Jacobite, which means he believes that James II and his heirs, the Stuarts, are the true kings of England and Scotland. Both of these political positions also have religious connotations: all Whigs were Protestants, and most Jacobites were Catholics. This immediately creates a confrontational dynamic between the two men, which explodes in the chapter "The Quarrel," when Alan taunts David for being a Whig one too many times.

But the moral and ethical differences—how loyalty and honor work, and most importantly, doing what is "right"—are not based so much on political or religious affiliations, but the place and manner of each man's upbringing. David has lived a sheltered, secure life in the Lowlands, instructed by Protestant religious leaders like Mr. Campbell. His status as a Whig means that he is unmolested by the government. Alan, on the other hand, is a rebel, and often a hunted man. His allegiance to his people caused him to desert the English army, so he lives under a constant threat of death, as do many of his countrymen. This Highland code of ethics is what leads Alan to protect the assassin of Colin Campbell by drawing the English soldiers' attention away. David protests being accused of the crime, rather than turning in the real killer: "The innocent should surely come before the guilty," he says. Alan responds, "Them that havena [have not] dipped their hands in any little difficulty, should be very mindful of the case of them that have. And that is the good Christianity." Alan's response is based on the assumption that Campbell's death is not a bad thing, and therefore the killer should be protected. David still does not agree, but is impressed: "Alan's morals were all tail-first; but he was ready to give his life for them, such as they were."

The other major problem with these issues occurs at the house of James Stewart. James tells Alan and David that he will have to give their names out as the killers of Campbell and paper them, meaning to have a warrant issued for their arrest. David again protests, claiming that the actual killer should be papered, to which both Alan and James respond with surprise and shock. In this instance, David is incapable of understanding their logic. Raised as he was in a community where problems were solved fairly by lawyers and courts, he knows nothing of clan rivalries, clan alliances, and the unfairness of a court system controlled by the English-loyal Campbells.

The primary place that Stevenson makes David's trip through Scotland as if he were going through a "foreign country" are the chapters focusing on David and Alan's flight through the Highlands. The Lowlands, which are mostly full of Whigs, would seem familiar to most English readers. But the Highlands (particularly the Highlands of the 1750s, a hundred years before Stevenson's birth) would seem like a "wild" place, where the Highlanders have their own code of ethics (see above) and live a very different life than the more cosmopolitan Lowlanders or the English reading public.

Most of the sense of the foreign in Kidnapped comes either from Stevenson's descriptions of nature or people. Some of the most unusual natural descriptions include the rocks in Chapter 20. David and Alan come upon a valley full of rocks jutting in different directions—a common feature of the Highlands, but more unusual in England and Europe. The two men then hide on top of one of these rocks, nearly boiling themselves in the process. There are many examples of Stevenson describing the natural aspects of Scotland, often rather unusual ones. David and Alan spend some time in a cleft in the middle of a mountain, cross numerous rivers and fords, and even crawl across a moor—a broad, flat, marshy land. They visit Cluny Macpherson, who lives in a kind of hidden tree-hut on a mountain. Also, throughout the flight, David encounters interesting examples of Highlanders, from a notorious blind robber to two different clan chiefs—James Stewart and Cluny.

By portraying Highland Scotland as a world apart from the familiar English world of his readers, Stevenson promoted the legend of the wild Scottish Highlands, which began half a century before with Sir Walter Scott's novel Rob Roy and continues to today with films like the science fiction epic Highlander.