Who is hinted at being the one who committed the murder? If this is the case, what part, if any does alan play in it?

Stewart exclaimed that soldiers would soon ransack the entire area and the news that Alan had been present would surface. James would have to create a wanted poster with Alan's name and another with David's. He figured that the Red Fox's relatives would do the same and it was James's only hope of avoiding some of their retribution.

Alan cried that he had brought David to this and now acted like a traitor. Alan asked David what he thought, who told them that they make posters of the man who had committed the crime, not of two innocent men. The Highlanders gasped, crying that they would not betray the Camerons. To David, this confirmed that the murderer was from the Cameron family.