Socrates, returning from service in the army, arrives at the Taureas palaestra, one of his "old haunts." He is greeted there by a number of friends and acquaintances, among whom Chaerephon ("who always behaves like a madman") runs up to Socrates to ask how he managed to escape from the brutal battle of Potidaea. News of the battle has just reached Athens. Socrates replies that he escaped "just as you see me now," and Chaerephon asks him to sit down and tell the story.
Socrates is led over to a group that includes Critias. Socrates answers questions about the army and the battle. Eventually, Socrates starts asking about Athens—the state of philosophy these days, whether any youth are particularly wise or beautiful, and so on. Critias points out a group of men just arriving who are the lovers of a remarkably beautiful young man named Charmides (the son of Critias's uncle Glaucon). Socrates recalls meeting Charmides when the young man was still a boy.
Charmides walks in. Socrates pauses in his narration to tell us how particularly bowled over he was by Charmides's looks. Generally, he says, he's a bad judge of beauty, since "all young persons appear beautiful" to him. But Charmides absolutely astonishes Socrates (and everyone else, not just the love-struck men but everyone, down to the smallest boy, "as if [Charmides] had been a statue.") Another troop of would-be lovers follows behind Charmides. Chaerephon asks Socrates what he thinks of Charmides's face, and Socrates admits it's beautiful. But Charmides's face is nothing, Chaerephon says, compared to his naked form, which is "absolutely perfect."
Socrates wishes that this "paragon" of beauty also had a noble soul, and is quickly assured that this is indeed the case. In that case, Socrates says, the company should first "ask him to strip and show us his soul" (i.e., talk with him before seeing him naked). Critias assures Socrates that Charmides (who, he adds, is already a good poet and philosopher) would be happy to talk. Socrates asks Critias to call Charmides over, noting that there would be no sense of "impropriety" in doing so because Critias is his "guardian and cousin." Critias has someone call Charmides and tell him that Critias wants him to come over and see a physician about the illness he's been complaining of—a headache in the morning. Critias persuades Socrates to pretend that he has a cure for headaches.
Charmides comes and sits down, among the riotous jostling of people who want to sit near him. As he sits down between Socrates and Critias, Socrates confesses (to the readers) that he became suddenly very nervous about talking with Charmides. Not only is there a whole crowd looking on, but Socrates is going crazy with lust (having caught sight of the "inwards of [Charmides's] garment" as the young man sat down. Socrates experiences a "wild-beast appetite," and thinks of Cydias's saying, on love, that one should not "bring the fawn in the sight of the lion to be devoured by him." Nonetheless, when Charmides asks after the headache cure, Socrates answers, "with effort," that he does indeed have one: it consists of a special leaf, accompanied by a spoken charm.
It becomes clear that Charmides knows Socrates's name, and that the young man has heard rumors about him (in addition to meeting Socrates at a young age). Socrates says this makes him more comfortable in explaining the nature of the aforementioned charm. He begins with the example of physicians, who never seek just to cure one part of the body without making the whole body well (to do otherwise would be "the height of folly"). Charmides agrees that this is a good policy. Socrates, beginning to feel less nervous now, tells Charmides that he received this "charm" from one of the mystical physicians to the king of Thrace (Zalmoxis), physicians he encountered in the army. These doctors told him that, although the Hellene policy of curing the whole body instead of a part is good, it's even better to start with the soul, and specifically the state of "temperance" that defines a healthy soul (thus the soul-body whole is cured, not just the body). Socrates claims to have taken an oath always to proceed this way.