The Empire is being held to ransom by the Barbarians. On the eve of the coronation of the 12-year-old Romulus Augustus, his mentor, the shaman Ambrosinus (Ben Kingsley), predicts disaster. His worst fears are realised as the Goths sack the once-great city of Rome and capture the last Emperor and his protector. They are imprisoned on the historic island of Capri, where Romulus is destined to discover the mythical sword of Cæsar that holds the prophecy -

'One edge to defend, one to defeat; In Britannia
was I forged... to fit the hand of he... who is destined to rule.'

One legionnaire survives to escort his Emperor to safety - the boy's loyal bodyguard, Aurelius (Colin Firth). Aided by a mysterious black-clad Byzantine warrior (Aishwarya Rai) and Ambrosinus' strategic cunning, Aurelius frees Romulus only to face betrayal and a fight for their lives. With the world against them, their only course of action is to reach the one legion loyal to Rome. They face a perilous trek across a continent to Britain in search of The Last Legion. There, a new myth - destined to span the centuries - is waiting to rise.