As usual, d’Artagnan and his friends are out of money. On this occasion, their need is particularly great because it will cost money to send the dangerous messages that will thwart Milady's mission. Because of this, D'Artagnan finally gives in and sells his precious diamond ring from the Queen. Its sale provides plenty of money for everything they need to do. 

The four friends elect Aramis, who is the most educated of the group, to write the letters. First he writes a subtly worded note to Milady's brother-in-law, Lord de Winter. In it, he explains truthfully that Milady was already married before she married Lord de Winter's brother, that she has a fleur-de-lis branded on her shoulder, and that she wants Lord de Winter dead so she can inherit his money. The four friends hope that Lord de Winter will somehow manage to bring Milady to justice, thus preventing themselves and everyone else from her treachery in the future.

The next part of the plan is more difficult: the friends must warn Queen Anne about the danger to the Duke of Buckingham. Aramis writes a note to his supposed cousin, whom everyone by now knows to be his mistress, the Duchess de Chevreuse. She is a good friend of the Queen's, and she is capable of sending a message that will not be intercepted by the King or the Cardinal.

In his letter, Aramis does not dare state his secrets too openly lest the paper fall into the wrong hands. Instead he writes that he dreamed Buckingham was dead, and that his dreams often come true. He mentions this right next to a paragraph about the Cardinal, knowing that his mistress will understand that the Cardinal is planning Buckingham's assassination.

Musketeers are not allowed to leave camp in the middle of a military campaign, so they have to make lackey's carry the messages. Aramis's servant, Bazin, takes the letter to Madame de Chevreuse, who soon replies with a letter that is just as subtly worded as Aramis's. She says her "sister"—by whom she really means the Queen—hopes that Aramis's dream will not come true. She thanks Aramis for his help and asks him to write again whenever he can do so safely.

D'Artagnan's servant, Planchet, takes the other letter to Lord de Winter. Before he leaves, he secretly promises d'Artagnan that he will warn de Winter about the plot against Buckingham as well. The lackey rides off, and the Musketeers nervously await his return. He is gone for sixteen full days, and when he arrives back, he carries the following a reply from de Winter that says only: "Thank you, be easy."