Roman centurion Marcian is captured by Attila the Hun en route to Constantinople, but escapes. On arrival, he finds the eastern Roman emperor Theodosius plotting with Attila to look the other way while the latter marches against Rome. But Marcian gains the favor of Pulcheria, lovely sister of Theodosius, who favors a united Empire.

As the Roman empire crumbles, young Romulus Augustus flees the city and embarks on a perilous voyage to Britain to track down a legion of supporters.