Celtic fantasy and first of a series from the author of the recent Pendragon Cycle Trilogy, In the Hall of the Dragon King, etc. The aristocratic Simon Rawnson and his American friend, narrator Lewis Gillies, are postgraduate students at Oxford, free to go chasing impetuously off to the far north of Scotland in pursuit of an extinct beast supposedly sighted by a farmer. Simon clambers inside a cairn and vanishes. Helped by a Celtic expert, the mad professor Nettles, Lewis follows--and finds himself in Albion, a Celtic paradise (our world and Albion are apparently coming unravelled, however). In Albion, the two friends both become warriors, only to take opposing sides in a power struggle, with Lewis as warrior Llew siding with the good Phantarch, while Simon joins evil Nudd, King of the Underworld. Only by bringing Simon back to our world, Lewis reasons, can the evil be abated. Lawhead treats his Celtic lore with respect; the upshot is well handled and pleasingly restrained, a solid and readable opener for the series.