France's King Louis XIII is overjoyed when a son and heir to the throne is born to him. When the queen then gives birth to a twin, however, Cardinal Richelieu fears the second-born boy could spark a revolution, and to secure France's peace he has the child spirited away to Spain to be brought up in secret. Sadly, guarding that secret means Constance, D'Artagnan's beloved, must be sent away to a convent. On learning of it, D'Artagnan gathers the Musketeers to try to free her. But Richelieu outwits them and banishes the Musketeers for good.