Frustrated by his wife's infertility, Louis makes a foolish statement, suggesting it were best if she were dead. As a result, Richelieu sends Irish gunman Gallagher and his gang to kill her while she is travelling with the Musketeers. Sending their friends back for reinforcements, Aramis and Athos take her to a convent for sanctuary, where Aramis is surprised to see his former love, Helene is one of the nuns, though she and the Mother Superior prove themselves very capable in the subsequent siege. However, it is with the queen that Aramis grows intimate, to Athos's horror. The siege is lifted, the queen saved and the king contrite whilst Richelieu manages to frame somebody else for the assassination attempt.

Milady seeks her revenge against the Musketeers. Will the Musketeers outwit her or will she destroy them by manipulating their weakest link; D'Artagnan?