There is a scene in Kidnapped in which David Balfour describes the misery of his ‘night tramps’ with Alan Breck Stewart through the Scottish Highlands as they try to evade capture for the suspected murder of Colin Campbell. To compound matters, David and Alan have fallen out after Alan had gambled and lost all of David's money. ‘This was a dreadful time,’ remembers David, ‘rendered the more dreadful by the gloom of the weather and the country.’ At one point during their flight in the dark heather he hears the rain-steeped river in the valley below, ‘now booming like thunder, now with an angry cry’. After this the narrative then switches register, as David admits:

With his characteristic economy Stevenson packs an enormous amount into these two sentences as the passage seamlessly weaves together religious and cultural knowledge. To begin with, he has David Balfour describe a Scottish folk belief about the Water Kelpie, whose reality David does not accept but in that moment of terror he ‘could well understand’. However, Alan at least ‘half believed’ the story, judging from the observation that ‘when the cry of the river rose more than usually sharp’ he would ‘cross himself in the manner of Catholics’. David, a Presbyterian Lowlander, while educated enough in religious matters to be ‘little surprised’, is nevertheless ‘shocked’ at the sight of his Highlander friend adopting what he considered to be a superstitious custom. David therefore learns something about Alan's lived faith while the reader gains an understanding of the differences between neighbouring Christian denominations. All of this takes place in the middle of an excursus on the persistence of Scottish folk beliefs in an enlightened age.