Messalina (played by the stunning Betty Roland) is a power-hungry nymphomaniac determined to become Empress of Rome. She attracts Caligula's attention by fighting in the gladiator arena, and it is not long before she accomplishes her goal, upsetting the Emperor's youngest sister Agrippina, who hopes that her son Nero will one day rule Rome. Agrippina successfully plots Caligula's demise, but Messalina snubs her by immediately jumping into bed with his successor, Claudius. But naughty old Messalina can't commit to one man and shags everyone she meets, including a grotesque but well-endowed brothel frequenter, a randy midget, her eunuch(!?!?) and an ex-lover. When she becomes pregnant and it is clear that the father is not Claudius (because he has been fighting in foreign lands), Agrippina sees her chance to finally get rid of her nemesis.