Louis has the Musketeers bring his traitorous brother Gaston to Paris, despite the latter's exile, and extends the hand of friendship to the relative who tried to overthrow him. Meanwhile, the veterans of Paris grow restless when Louis refuses to pay their pensions. When Gaston loses a purse containing incriminating letters, Feron sees an opportunity to benefit himself.

Lucien and Feron stage a prison breakout to cover Lucien's theft of the king's gold reserve. D'Artagnan befriends an insane prisoner who thinks that he's Louis, while Aramis and Constance discover that an imprisoned locksmith's wife is being held as leverage to force the man to assist in the robbery.