D'Artagnan is forced to join forces with Milady to save Constance, who was kidnapped before his eyes. But as war is declared and Athos, Porthos and Aramis have already joined the front, a secret from the past shatters old alliances.

D'Artagnan arrives in Paris trying to find his attackers after being left for dead, which leads him to a real war where the future of France is at stake. He aligns himself with Athos, Porthos and Aramis, three musketeers of the King.