The siege of La Rochelle allows the cardinal an opportunity to fulfill two aims. First, he wants to rid France of its enemies, and second, he wants to take vengeance on a rival. That is, the cardinal was once in love with the queen, Anne of Austria, but she rejected him and accepted the romantic overtures of the duke of Buckingham, who is now declaring war on France, hoping to return triumphantly to Paris and rendezvous with the queen.
Since the king has a fever and cannot go to the battlefront, the musketeers are forced to remain behind with him. Thus, for the first time, d'Artagnan is separated from his friends. Since he has made no friends among the guards of his own division, he is out walking alone on an isolated road at twilight when he suddenly sees the end of a musket on one side of the road and another musket on the other side. He quickly and instinctively takes cover when both muskets are fired at him and he manages to escape before the ambushers can reload. He ponders the meaning of the attack and rejects the idea that it was the enemy who fired on him because the muskets were not military weapons. D'Artagnan cannot fathom the cardinal's stooping to ambush; finally, he decides that Milady was involved.
Two days later, Monsieur des Essarts, commander of the guard, informs d'Artagnan that the commander-in-chief is going to call for volunteers for a dangerous mission. D'Artagnan volunteers and, not surprisingly, he is made leader of the expedition. Two other officers and two ordinary soldiers also volunteer. The mission is to discover whether the enemy, on recapturing a bastion, left it guarded or unguarded. They will have to get dangerously close to the bastion. When they are approaching it, a volley of shots rings out, wounding one of the officers. Then two more shots ring out, and d'Artagnan is very nearly killed. He realizes instantly that the shots did not come from the enemy but that they came from behind him. He also realizes that the two common soldiers are trying to kill him and make it seem as though the enemy killed him. In fact, d'Artagnan believes, the two traitorous soldiers are the same two men who tried to ambush him earlier; he is absolutely certain that Milady conceived this plot.
D'Artagnan attacks and disarms the two soldiers. One of them manages to escape toward the bastion, but is shot by the enemy. The other soldier begs for mercy and confesses that they were indeed hired by Milady and that the wounded soldier has a letter from her. The letter chides the two soldiers for allowing Constance Bonacieux to escape and warns them not to allow d'Artagnan to escape.
Even though the letter isn't signed, d'Artagnan knows that it is from Milady, and he realizes anew what a terrible craving for revenge she has. Back at camp, he is accorded the reception of a hero, and his exploits are extolled by the entire command.
One morning in early November, d'Artagnan receives a letter telling him that the three musketeers are confined to quarters because of rowdy behavior, but that they have sent him twelve bottles of Anjou wine. D'Artagnan offers to share the wine with one of the guards, but just as they are about to drink up, a commotion announces the arrival of the king, the cardinal, and also the three musketeers.
D'Artagnan thanks his friends for the wine and asks them to join him in drinking it. The musketeers tell him that they didn't send the wine, and all four of them simultaneously realize that Milady is responsible for the gift. At that moment, one of the guards who drank some of the wine falls down, poisoned. The four friends realize again that Milady is a worse threat than the enemy, and they decide to try to do something about her. D'Artagnan tells them that Constance Bonacieux is in a convent somewhere, but he doesn't know where. Aramis assures him that he will find the woman soon.
These two chapters reveal to the reader what a powerful enemy d'Artagnan made when he saw the branded fleur-de-lis on Milady's naked shoulder. The extent of her drive for revenge is enormous. Three separate attempts on d'Artagnan's life have been made, and it is only because of d'Artagnan's alertness and daring during the first two attempts, and purely by accident during the incident of the Anjou wine that he is still alive. Even though these attemps to kill d'Artagnan are foiled, we will see in future chapters that Milady will never give up. She has vowed to see d'Artagnan dead — or die trying.
The beginning of Chapter 41 again emphasizes that the cardinal's persecution of the French queen is partly a result of jealousy: the queen prefers Buckingham to the cardinal. Dumas is insistent that the cardinal not be seen as merely a clever manipulator of people, but as a three-dimensional man, one spurned by the queen of France.
It is also worth noting that the separation of d'Artagnan from his friends sets the stage for several attempts on his life. Since his only close friends until now have been the three musketeers, it is believable that he would go for solitary walks. Were his three friends with him, d'Artagnan would never have been attacked by two cowardly dastards. However, because he is alone, he is attacked. Similarly, because he is alone and bored and eager to put some adventure into his life, he volunteers for a dangerous mission. D'Artagnan is continually trying to establish his own sense of identity and display leadership qualities — apart and separate from the three musketeers.
Lest someone think that d'Artagnan would not likely know that the unsigned letter in the wounded solder's uniform was from Milady, remember that he is familiar with Milady's handwriting. He has received love notes from her and, because of Kitty, he has been able to intercept love notes which she wrote to Count de Wardes. Dumas ties up most of his complicated plot elements very neatly and effectively.