"Why, David," said he, "the innocent have aye a chance to get assoiled in court; but for the lad that shot the bullet, I think the best place for him will be the heather."... When it came to this, I gave Alan up. But he looked so innocent all the time, and was in such clear good faith in what he said, and so ready to sacrifice himself for what he deemed his duty, that my mouth was closed. Mr. Henderland's words came back to me: that we ourselves might take a lesson by these wild Highlanders. Well, here I had taken mine. Alan's morals were all tail-first; but he was ready to give his life for them, such as they were.

This quote, from Chapter 18 is one of the main instances where David and Alan have a moral disagreement. The primary focus of Kidnapped is on the friendship between these two, and David's growing understanding of Alan's Highland ethics and attitudes. This scene is key because David, while not agreeing with Alan's belief that the killer should go free, admires his devotion to his cause and his people.