Assigned to escort privateer Emile Bonnaire from Le Havre to Paris the musketeers have to thwart an escape attempt by his wife Maria and an ambush by his aggrieved ex-business partner Meunier and his men, during which Porthos is wounded, necessitating a sojourn at a deserted château. Athos explains it belongs to his family and was where he married Milady. Bonnaire is revealed to be a slave owner and, on arrival in Paris, bribes Richelieu into forming a partnership operating tobacco plantations in the New World, using slaves as a work force. However there is another faction out to capture Bonnaire and the musketeers are braking no rules in handing him over to them.

On her journey to Paris the queen of England, Henrietta Maria, also the sister of King Louis is robbed of the crown jewels, which has to be sold in order to finance England's armed forces. The Musketeers quickly discover the thief to be Émile Bonnaire, a flamboyant but pathetic criminal they encountered previously. Athos, Porthos and D'Artagnan pressure Bonnaire into leading them to the diamonds' buyers to recover them. Aramis on the other hand, reconnects with Pauline, a childhood friend he grew up with in a bordel where their mothers lived and worked. She is set to marry a French nobleman but is being blackmailed by someone threatening to reveal the circumstances of her childhood, and Aramis tries to resolve the situation peacefully.