In 1625 France, d’Artagnan (a poor young nobleman) leaves his family in Gascony and travels to Paris to join the Musketeers of the Guard.
D’Artagnan falls in love at first sight with Constance Bonacieux. She works for Queen Anne of France, who is secretly conducting an affair with the Duke of Buckingham. The King, Louis XIII, gave the Queen a gift of diamond studs but she gives them to her lover as a keepsake. Cardinal Richelieu, who wants war between France and England, plans to expose the tryst and persuades the King to demand the Queen wear the diamonds to a soirée that the Cardinal is sponsoring. Constance tries to send her husband to London but the man is manipulated by Richelieu and does not go, so d’Artagnan and his friends intercede. En route, the Cardinal’s henchmen repeatedly attack them and only d’Artagnan reaches London. Although Milady stole two of the diamond studs, the Duke of Buckingham provide replacements while delaying the thief’s return to Paris. D’Artagnan is thus able to return a complete set of jewels to Queen Anne just in time to save her honour.