Diane de Poitiers is in a childless marriage with count de Breze. When he is charged with treason, Diane visits king Francis I to successfully plead for her husband's life, something that start a rumor that she has offered her own services in return. Her husband reject her, leading Francis to ask her to come to the royal court to teach prince Henry how to be a gentleman. The prince and Diane fall in love and she becomes the prince's mistress, something that makes his wife Catherine de Medici her enemy. When the prince becomes the king of France, Diane is wielding considerable influence over him.