D'Artagnan arrives in Paris to join the Musketeers of the Guard and finds himself in the middle of a war for the future of France. With the help of Athos, Porthos, and Aramis, he faces dangerous adversaries, including a malicious woman and a conspiracy against the King.
In order to save Constance, who was abducted in front of him, D'Artagnan reluctantly teams up with Milady. However, with the declaration of war and the other Musketeers already at the front lines, a hidden secret from the past puts their alliances in jeopardy.