In
Venice, the
musketeers Athos,
Porthos, and
Aramis, with the help of
Milady de Winter, steal airship schematics made by
Leonardo da Vinci. However, they are betrayed by Milady, who incapacitates them and sells the blueprints to the
Duke of Buckingham. A year later,
D'Artagnan leaves his village in
Gascony for
Paris in hopes of becoming a musketeer as his father was, only to learn that they were disbanded. At a rural bar, he challenges
Captain Rochefort, leader of
Cardinal Richelieu's guard, to a duel after being insulted by him, but Rochefort merely shoots him while he is distracted. Once in Paris, D'Artagnan separately encounters Athos, Porthos, and Aramis and, accidentally offending all three, schedules separate duels with each. Athos brings Porthos and Aramis to the duel as his seconds, causing D'Artagnan to realize their true identities. Richelieu's guards arrive to apprehend them, but, inspired by D'Artagnan, the musketeers fight together and win. All four are summoned before the young King
Louis XIII and Richelieu urges him to execute them, but
Queen Anne is impressed by their bravery and the king decorates them instead. Richelieu instructs Milady, now his accomplice, to plant false love letters among Queen Anne's possessions, and steal her diamond necklace, and take it to the
Tower of London in order to frame her as having an affair with Buckingham, which would force King Louis to execute her and declare war on
England. By this point, the people would demand a more experienced leader: Richelieu himself. In order to secure her own position, Milady demands that Richelieu declare in written authorization that she is working on behalf of France. The false letters are found and given to King Louis, who is advised by Richelieu to set up a ball at which Queen Anne would be forced to wear the necklace. If she does not, then it will be believed her affair is real, and there will be war. Queen Anne's
lady-in-waiting Constance Bonacieux discovers Richelieu's plan and pleads with the musketeers to stop him. They follow Milady and Buckingham to
London, while Constance is captured by Rochefort for helping the musketeers to escape from him. In London, Milady tells Buckingham the musketeers have arrived to take revenge on him and exposes to him all their tendencies in battle. D'Artagnan is captured, but he is in fact acting as a decoy following the plan Milady would have
expected the Musketeers to follow, allowing his associates to hijack Buckingham's airship and rescue him. Milady's getaway
coachman reveals himself as the musketeers' manservant Planchet and delivers her to his masters, who retrieve the necklace from her. Athos prepares to execute Milady for her treachery but is hesitant, and she leaps off the airship, seemingly dying on her own terms. The musketeers depart back to Paris, only to be intercepted by Rochefort in a much larger airship, for Milady had given Richelieu copies of da Vinci's blueprints. Rochefort offers to exchange Constance for the necklace, but captures D'Artagnan and mounts an assault as soon as he retrieves the jewels. His superior airship has the upper hand and severely damages the opposing vessel, but the musketeers use the clouds to rally and counterattack. The fight ends when both ships ram each other, crashing onto
Notre Dame. On the roof, D'Artagnan challenges and ultimately kills Rochefort, recovering the necklace in the process. Constance is sent ahead to quietly return the necklace to Queen Anne. The musketeers arrive at the ball and, for the sake of King Louis and his people, lie by claiming that Rochefort tried to sabotage an airship that Richelieu built for them and that they executed him for his treason on Richelieu's permission. To convince the king, Athos presents Milady's authorization, which the former accepts. Richelieu, satisfied, offers the musketeers a place in his guards, but they refuse, and Richelieu vows revenge. Meanwhile, Milady is found alive in the
English Channel by Buckingham, who declares his intention to exact revenge as they advance towards France with a massive fleet of battleships and airships. ==Cast==