It's true, Ewen is the one who spends most of the book In Peril of Death, so it makes sense that I figured he would be the one to die in the sand at the end. But he was not! Instead it was Keith! And Keith is weirdly relieved, because at least this means he doesn't have to betray Ewen after all.

...I do like the idea of Ewen taking Keith to the ship and Keith gets to not betray Ewen and ALSO not die, though.