Alexandre Dumas’s classic adventure novel, Les trois mousquetaires (The Three Musketeers), follows the journey of d'Artagnan, a spirited young Gascon gentleman who travels to Paris with dreams of joining the King's Musketeers.
Upon his arrival, a series of misunderstandings leads him to challenge three of the most formidable musketeers—Athos, Porthos, and Aramis—to consecutive duels. However, before the duels can commence, they are interrupted by the guards of Cardinal Richelieu, who attempt to arrest them for illegal dueling. D'Artagnan sides with the musketeers, helping them defeat the guards, which earns him the lifelong friendship and respect of the trio.
The plot intensifies as d'Artagnan becomes entangled in court intrigue involving King Louis XIII, Queen Anne of Austria, and the powerful Cardinal Richelieu. The Cardinal seeks to expose an affair between Queen Anne and the English Duke of Buckingham to humiliate the monarchy. When the Queen gifts Buckingham a set of diamond studs, Richelieu convinces the King to demand that she wear them to an upcoming royal ball. To save the Queen’s honor, d'Artagnan and the three musketeers embark on a perilous mission to England to retrieve the studs. Despite facing ambush and separation along the way, d'Artagnan successfully secures the jewelry and returns just in time to thwart the Cardinal's scheme.
The conflict deepens with the introduction of Milady de Winter, a beautiful and ruthless agent of Cardinal Richelieu. D'Artagnan uncovers her dark past, learning that she was once married to Athos, who thought she was dead after discovering she was a branded criminal. Seeking revenge against d'Artagnan for exposing her secrets, Milady orchestrates multiple assassination attempts against him. As the Siege of La Rochelle begins, polarizing France and England, Richelieu sends Milady to England to assassinate the Duke of Buckingham, which she successfully executes by manipulating a Puritan officer named Felton.
Milady then flees back to France and hides in a convent, where she discovers Constance Bonacieux, d'Artagnan’s beloved. Out of sheer malice and revenge, Milady poisons Constance just before d'Artagnan and the musketeers arrive. Devastated by her death, the four friends track Milady down, capture her, and subject her to a formal trial for her numerous crimes, including the murders of Buckingham and Constance. She is found guilty and executed by a red-cloaked executioner. In the aftermath, Cardinal Richelieu, impressed by d'Artagnan's resourcefulness and bravery, pardons him for his actions and promotes him to the rank of lieutenant in the Musketeers, while the other three musketeers eventually pursue separate paths in life.