The author tells us that even though the heroes of the story have names that end in “os” and “is,” which sound mythological, we’re not supposed to go down that analytic road. He also tells us that this preface will make that clear.
The author was doing research in the library one day when he found the memoirs of a certain Monsieur D’Artagnan (also referred to as just D’Artagnan). The author took them home, read them, and was particularly struck by the passage in which D’Artagnan goes to meet with the captain of the Musketeers (that would be Monsieur de Tréville), and while there he meets three young men by the names of Aramis, Athos, and Porthos. The author is intrigued by these names, deciding that they must be pseudonyms, and traces the archival record for other mentions of these young men.
The author then discovers the memoirs of the Comte de la Fère, and within them, the names of Porthos, Athos, and Aramis. He begs permission to publish these memoirs, and receives it.
The story that follows, says the author, is the Comte de la Fère’s account of history.