D'Artagnan, a headstrong young man from the impoverished Gascon aristocracy, goes to Paris with dreams of joining the Musketeers. Three inseparable Musketeers become his new best friends and mentors, along with their captain, Treville. Even though he joins the guard, d'Artagnan knows he must distinguish himself somehow to achieve his dream of becoming a Musketeer. He sees his opportunity when Bonacieux asks for help finding his kidnapped wife. This mission draws d'Artagnan and his friends into court intrigue and the rivalry between the king and the cardinal. D'Artagnan defeats various expert swordsmen in the cardinal's guard, and makes a heroic journey to get the queen's diamonds from the duke. Over time, d'Artagnan takes on an increasing leadership role in his friend's group. When d'Artagnan becomes infatuated with Milady and eventually crosses her, he must sidestep her revenge attempts. D'Artagnan and Athos enact a plan to punish Milady and to end her evil ways. The cardinal admires d'Artagnan's initiative, giving him a commission to be a lieutenant in the Musketeers.
Athos is calm, measured, and circumspect in contrast to d'Artagnan's hotheaded impulsiveness. He is a father figure to d'Artagnan but also admires him. Athos, representing the past, has left behind an aristocratic life of luxury to become a Musketeer. He is a man of few words and dark moods, hinting of some tragedy, but he keeps his secrets to himself for most of the book. Athos later reveals the cause of his fixation on the past: he had hanged his young bride after discovering she had the mark of a convict. He and d'Artagnan realize Milady is Athos's wife (who inexplicably survived). Athos confronts her at the Red Dovecot and takes her carte blanche. Later, he spearheads the hunt for Milady and brings her to trial. Athos returns to his aimless and unambitious life as a Musketeer, happy to forego a commission and serve under d'Artagnan. The epilogue shows Athos retired and leading a quiet life, having acquired a small piece of land.
Large, strong, and good-looking, Porthos uses his natural gifts to his advantage by securing a bright future through a wealthy mistress, Mme. Coquenard. She keeps him well fed and handsomely outfitted. When he eats thin soup for dinner at her house, Porthos fears the wealth of her elderly husband is not what he hoped. Although he is as brave and loyal as the other Musketeers, Porthos is somewhat hapless in following the thread of conversations or Athos's plans toward the end of the book. Porthos's real genius is keeping Mme. Coquenard enthralled by hinting at all the rich noblewomen who want him. The epilogue shows Porthos, having left the service, about to marry the recently widowed Mme. Coquenard and her enormous fortune. Representing hope for the future, Porthos looks ahead to opulence and security.
Aramis, representing the present, left the seminary for the present moment to become a Musketeer. He often deliberates resuming immediately, especially when he thinks a certain mystery lady has forgotten him. She is a noblewoman with connections to the queen—Aramis's gallant discretion and protection of her identity make him the perfect lover. Her letters are later signed "Marie Michon," said to be a seamstress. Eventually, she is revealed to be the exiled Madame de Chevreuse, the queen's best friend. Milady considers Aramis important because his secret could be useful. The epilogue reveals Aramis's moment as a Musketeer has ended, and he has resumed his studies for the priesthood, but no one knows where.
The cardinal uses his far-reaching power—his personal guard and his network of spies—to try to control the king, the queen, and France. He and the king are friends but also rivals: the cardinal's guards and the king's guards are enemies, instigating battles and duels and avenging one another's deaths. The cardinal has personal as well as political reasons for some of his schemes: the queen had rejected him in the past, and later fell in love with the Duke of Buckingham. The cardinal is jealous of the duke. Also, as a high-ranking leader of the Catholic Church, the cardinal tolerates the fact that the state of La Rochelle is in Huguenot hands until the English plan to get involved. He must, therefore, prevent England from sending support to La Rochelle and undoing the efforts of the siege—this is the perfect opportunity to assassinate the duke. The relationship between the cardinal, d'Artagnan, and the three Musketeers is mutually polite—the cardinal wants the four friends on his team. At the end, the cardinal gives d'Artagnan a commission as an officer in the Musketeers.
Milady de Winter
Milady acts as a spy for the cardinal and uses her beauty, charm, noble bearing, and acting ability to infiltrate the aristocracy of Europe. She speaks French and English fluently, so she can pretend to be a native of either land. The cardinal sends Milady to cut the queen's diamond studs off the duke, which she does willingly—the duke having spurned her in their own love affair. She vows revenge against d'Artagnan when he pretends to be the Comte de Wardes. He also learns her secret when he sees her fleur-de-lis brand: not only is she a convict, but she is also the wife of Athos, presumed dead. Milady also wants to kill her brother-in-law Lord de Winter for the inheritance—he suspects she already killed his brother, her husband. The cardinal instructs Milady to find a willing assassin, a religious fanatic whom she can incite to kill the duke. Lord de Winter gets wind of the plot and locks her up in his castle where she escapes with the help of a Puritan named Felton by seducing him with religious fervor. Milady then tracks Mme. Bonacieux as part of her revenge plot against d'Artagnan, but running just ahead of the Musketeers, Milady quickly poisons her. The Musketeers and Lord de Winter catch up with Milady, condemn her for her crimes, and behead her.
Treville is the perfect role model for d'Artagnan: a self-made man from Gascony who started with nothing and rose through the ranks with loyalty and courage to become not only captain of the king's elite guard, but a friend of King Louis XIII. Treville becomes a friend and mentor to d'Artagnan, securing him a place in the regiment of Dessessart so he can work his way up to Musketeer. Treville and his men share a mutual respect and loyalty. The men would gladly die for their leader.