In the dreaming spires of Oxford, graduate student Lewis Gillies and his impulsive roommate, Simon, drive north to get a mythical creature inside a misty glen in Scotland. Once there, Simon vanishes through a hole in the cairn, and Lewis follows him to a mystical place where two worlds meet, in the time-between-times. There, where Celtic champions, magic, and treachery weave the stunning and brutal land known as Albion, Lewis finds Simon. And there, schooled being a warrior, he is thrust to leading of a titanic struggle between light and darkness-a hideous, onrushing darkness that could devour not only a kingdom but two worlds.

The ancient Celts admitted no separation between this world and the Otherworld: both were delicately interwoven, each reliant on the other. The Heaven War crosses the thin places between this world and that, as Lewis Gillies comes face-to-face with a historical mystery-and a cosmic catastrophe in the making.