So everyone else has already said lots and lots about the Ewen/Keith, but I remember reading this for the first time, and what struck me most wasn't the Ewen/Keith story at all, but the Ewen/Lachlan story, and Lachlan's death and the tragedy of his arc. It's all set up in the prologue with Lachlan's desperate, unreasoning love of Ewen and his protectiveness and his willingness to disregard Ewen's wishes to do what he sees is best for Ewen, and Ewen's relative carelessness about the depths of Lachlan's devotion - and here it all come to fulfillment, where Lachlan, believing Ewen dead and Keith his betrayer, finally achieves everything he wants and then some: first he stabs Keith and achieves revenge, and then he finds the Ewen is alive and right beside him. For about ten seconds, all Lachlan's dreams have come true. Then Ewen turns it all on its head, curses Lachlan and is willing to be recaptured or killed rather than leave the dying Keith. And then when Lachlan understands what he's done and goes to Ewen for forgiveness, Ewen can't - and so Lachlan kills himself.

And you have to wonder what Angus Og made of this - is he Lachlan's nephew or his younger brother, I can't remember? We never see any sign of his reaction other than wanting Ewen to escape, even as Lachlan goes to his death.

But they're odd parallels, Keith and Lachlan, both in different ways dying here because of their love for Ewen. In some ways, it's not Keith I want fix-it fic for, but Lachlan.