Britannia is overrun by migrants who speak a strange language and worship heathen gods, and Bishop Brice is given the job of trying to persuade the Romans to send a legion to drive them out. But the Romans have their own problems and are reluctant to spare any of their dwindling forces. However, a bishop called Germanus, eager to suppress the Pelagian heresy, manages to put together a small force to help the Britons. His religious zeal leads to a...