Marcus Caius, a Roman legionnaire in the Tenth Legion, has served for the entirety of Julius Caesar's Gallic War. Lately, however, British soldiers have begun to reinforce the Gallic army. With the province of Belgica now under control, Caesar plots a reconnaissance-en-force to the island of Britannia before the onset of winter, and Marcus is to be among the force. Before long, the expedition suffers setbacks, and the Legionnaires are left to fend for themselves and find a way to cross the channel back to Gaul before it is too late. Will there ever be a time when the Romans are not despised for their warring ways? As Caesar and his forces attempt to conquer Britannia, facing fierce resistance, that question comes to the fore again and again.