After more than four hundred years of Roman rule, the island its conquerors called Britannia was abandoned—left to its own devices as the Roman empire contracted in a futile effort to defend itself from the barbarian hordes encroaching upon its heart. As Britannia falls into anarchy and the city of Viroconium is left undefended, two cousins who remained behind when the imperial forces withdrew pursue very different courses in the ensuing struggle to unite the disparate tribes and factions throughout the land.

Passionate, adventurous Dinas recruits followers and dreams of kingship. Thoughtful Cadogan saves a group of citizens when Saxons invade and burn Viroconium, then becomes the reluctant founder and leader of a new community that rises in the wilderness. The two cousins could not be more different, but their parallel stories encapsulate the era of a new civilization struggling to be born.