Generations ago, the people of the White Mare migrated westward, through the great forests, until they met and clashed with the people of the Cities of the Mothers. They brought war to the cities, but in the end they made peace through alliance and marriage.

But now war threatens again.

Now there is something rumbling across the plains, coming from the east: a dreadful new weapon wielded by the tribes of the east as they once again begin to push westward. Rhian, a potter's daughter with the gift of seeing, has dreamed of these terrifying war chariots. Emrys, the King's son, has seen them at the edge of his kingdom.

Together, they must try and find a way to defend the Cities of the Mothers from a new invasion.