According to 2001 testimony from an 89-year-old descendant of the Stewart family, the actual Appin murder was planned and carried out by four Jacobite Stewarts working in cahoots. The fatal shot was fired by a man named Donald Stewart, but James Stewart was still executed for it. For more on the background of this extremely belated Stewart confession, check out this article, titled "Who Killed Red Fox?"
Despite his crippling tuberculosis, Robert Louis Stevenson was a great traveler for most of his life. He wrote one really memorable account of a walking tour in France called Travels with a Donkey in the Cevennes. For a really marvelous account of him trying to get his donkey to move by yelling at it and poking it in the butt with a stick, check out this Project Gutenberg edition.