After burning Rome, Emperor Nero decides to blame the Christians, and issues the edict that they are all to be caught and sent to the arena. Two old Christians are caught, and about to be hauled off, when Marcus, the highest military official in Rome, comes upon them. When he sees their stepdaughter Mercia, he instantly falls in love with her and frees them. Marcus pursues Mercia, which gets him into trouble with Emperor (for being easy on Christians) and with the Empress, who loves him and is jealous.