In 1620s France, dreaded swordsman Gil de Berault returns from carrying out a mission for Cardinal Richelieu, and finds the Cardinal worried about growing opposition from the Huguenots in the south. The Cardinal also warns de Berault that dueling has been outlawed, and will henceforth be punishable by death. Gil, however, promptly disobeys the law and is indeed sentenced to death. The Cardinal offers to cancel the sentence if de Berault is able to capture the duke who is organizing plans for an uprising. Gil travels to the duke's castle and is allowed to stay as a guest, but the duke's wife and sister immediately suspect that he is a spy. He and his servant still make good progress, until he falls in love with the duke's sister, which complicates everything.