Harry Harrison, bestselling author of the acclaimed West of Eden trilogy, returns to alternate history with a major new work: a thrilling and thought-provoking adventure set on an Earth both similar to and radically different from our own. 865 A.D. Warring kings rule over the British Isles, but the Church rules over the kings. Powerful bishops and black-robed priests fill their cathedrals with gold, while threatening all who oppose them with damnation. But there are those who do not fear the priests, and they are the dreaded Vikings of Scandinavia. Among these Northern invaders, those who follow the Way of the Gods of Asgard carry the Hammer of Thor as their emblem, and they are sworn to increase mankind's knowledge and strength by conquest and by craft. And as Viking warlords cast hungry eyes upon a weak and divided Britain, the Way collides with the Church, launching an all-out war between The Hammer and the Cross. At the center of this bloody conflict is Shef, bastard son of a Norse raider and a captive English lady. A smith and a warrior, he is driven by strange visions that seem to come from Odin himself. Torn by divided loyalties, Shef alone dares to imagine new weapons and tactics with which to carve out a kingdom - and threaten the holy power of Rome itself!