The brightest and best musketeers of the King's Regiment, Athos, Porthos and Aramis, are dispatched by Captain Treville to find a missing musketeer carrying important letters on behalf of King Louis. But Cardinal Richelieu has plans to increase his political power and seeks to sabotage the good reputation of the musketeers.

Meanwhile, d'Artagnan travels from his family farm in Gascony to Paris to petition the king, but his peaceful plans are turned upside down when he is forced to find the musketeers and seek vengeance for the brutal murder of a loved one.

Will d'Artagnan bring the murderer to justice and can the musketeers protect king and country? Or will the cardinal triumph with the help of the beautiful and dangerous Milady?

The Musketeers are dispatched to Le Havre to collect the infamous merchant trader and explorer Bonnaire and bring him back to Paris to be reprimanded for breaking France's trade treaty. This straightforward mission soon descends into a treacherous battle, as they must defeat Bonnaire's surprising number of enemies.

Athos is forced to confront his past, which threatens to engulf him. Will he overcome his demons and help the Musketeers safely return to Paris, or will Bonnaire's enemies get the better of them?