Roman emperor Marcus Aurelius is poisoned by the henchmen of his mad son Commodus because he intends to hand power to the boy's more favoured and able adopted brother. But lacking sanity and authority, the usurper loses military control and Rome is overrun with barbarians. Historical drama, starring Alec Guinness, Christopher Plummer, James Mason, Sophia Loren, Anthony Quayle and Omar Sharif.

In the year 180 A.D. Germanic tribes are about to invade the Roman empire from the north. In the midst of this crisis ailing emperor Marcus Aurelius has to make a decision about his successor between his son Commodus, who is obsessed by power, and the loyal general Gaius Livius.