In an ancient cairn in the wilds of Scotland, Oxford student Simon Rawnson vanishes, seemingly into thin air. Where has he gone? Unsettling signs, a mysterious Green Man, and a Celtic circle chalked on the sidewalk point his roommate, Lewis Gillies, to an impossible answer...and an incredible destiny on the other side of a doorway between worlds.

There, where Celtic champions, magic, and treachery are woven together in the beautiful and brutal land called Albion, Lewis finds Simon. And there, schooled as a warrior, he is thrust to the front of a titanic struggle between light and darkness, a hideous, onrushing darkness that would devour not merely a kingdom but two worlds.