The Roman Emperor Marcus Aurelius dies, leaving the throne to his son Commodus, an arrogant thug who enjoys fighting as an amateur gladiator. Rome soon begins to suffer from Commodus' excesses, and his mistress Marcia (mistress of Commodus) tries to entice him towards a less dissolute lifestyle. In response, he discards her and forces his attentions on a chaste Roman aristocrat named Aemelia.