The Three Musketeers (Les Trois Mousquetaires) is a novel by Alexandre Dumas, père. It recounts the adventures of a young man named d'Artagnan after he leaves home to become a musketeer. D'Artagnan is not one of the musketeers of the title; those are his friends Athos, Porthos, and Aramis -- inseparable friends who live by the motto, "One for all, and all for one".
Dumas' version of the story covers the adventures of D'Artagnan and his friends, as they are involved in intrigues involving the weak King Louis XIII of France, his powerful and cunning advisor Cardinal Richelieu, the beautiful Queen Anne of Austria, her English lover, George Villiers, 1st Duke of Buckingham, and the Siege of La Rochelle. Adding to the intrigue are the mysterious Milady de Winter, and Richelieu's right-hand man, the Comte de Rochefort.