The sparing of Ardroy is one of those things that ought to feel too convenient or indulgent, and yet it's so beautifully written that it works. It's a brief reprieve for Ewen after a time of great darkness in his life - the collapse of his cause, the death of his foster brother Neil, his imprisonment (and all the agony of that time he believed Keith had betrayed him and he himself had betrayed Lochiel) - and although he has escaped to home for now, he knows that he will have to leave his beloved house and loch to be truly safe.

So what comes across is not "our protagonist's house is protected by the special forces that protect protagonists and their things," but the sense that for once the chances of war have turned in Ewen's favor rather than against him - after a long string where they've turned over and over against him.

Also, I love the description of Aunt Margaret and company tending the smoking fires so that it would look to all the countryside as if Ardroy is good and burnt. It seems so in character for her, and also very characteristic that she might touch off a spark of humanity in an English officer so he'd purposefully set the fire badly.