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?