The document summarizes the plot of The Three Musketeers by Alexandre Dumas. It introduces the main character D'Artagnan, a young man from Gascony who travels to Paris with a letter of introduction to Monsieur de Treville, the captain of the King's Musketeers. Upon arriving, he offends three musketeers named Athos, Porthos, and Aramis and is challenged to a duel by each of them. They are interrupted by the cardinal's guards due to laws against dueling. D'Artagnan joins forces with the musketeers to drive the guards away, becoming friends with the three men.