Part I, from "As we know, well before going that day..." to "...fertilization of the flower by the bumblebee."
Actually, Part I in the Penguin/Viking edition begins with a portentous phrase: "First appearance of the men-women, descendants of those inhabitants of Sodom who were spared by the fire from heaven." And then comes an epigraph:
Woman will have Gomorrah and man will have Sodom.--Alfred de Vigny
Still, we can't much blame Proust for laying it on a bit thick. He knew that the book was bound to attract bluenoses and censors, and that it had to have at least the appearance of moralizing if it had any hope of attracting even partly sympathetic heterosexual readers. Hence the long, dense, occasionally obscure portrait of the underground gay network, an embryonic version of what today is a community.
The section is a flashback to the concluding section of The Guermantes Way, and was originally written as a part of it. The narrator is lurking, on the lookout for the Guermantes carriage, so he can go ask the Duc and Duchesse if he really was invited to the Princesse de Guermantes's reception. And so he sees a startling encounter between Charlus, "potbellied, aged by the full daylight, graying," and Jupien.
Jupien ..., at once shedding the humble, kindly expression I had always seen him wear, had -- in perfect symmetry with the Baron -- drawn back his head, set his torso at an advantageous angle, placed his fist on his hip with a grotesque impertinence, and made his behind stick out, striking poses with the coquettishness that the orchid might have had for the providential advent of the bumblebee.
The botanical metaphor, based on a conversation at the dinner party in The Guermantes Way that the Duchesse had with the Princess of Parma about the pollination of a particularly beautiful plant which bore only female flowers, continues throughout the section. Meanwhile, Jupien leaves the courtyard, throwing flirtatious come-hither looks at Charlus, and is pursued by the Baron, who returns with him and disappears into his shop.
The narrator has "lost sight of the bumblebee," but he realizes that he has just witnessed "the good fortune reserved for men of the Baron's kind by one of those fellow creatures who may even be, as we shall see, infinitely younger than Jupien and better-looking, the man predestined so that they may receive their share of sensual pleasure on this earth: the man who loves only elderly gentlemen." He is self-conscious about his voyeurism, recalling "the scene in Montjouvain, hidden in front of Mlle Vinteuil's window," but he persists in it nevertheless -- to an almost absurd extent, sneaking into the empty shop that adjoins Jouvain's, listening through the "exceedingly thin partition" and climbing a ladder to peer through a transom. "From which I later concluded that if there is one thing as noisy as suffering it is pleasure, especially when there is added to it ... an immediate concern with cleanliness."
He also overhears the conversation between Charlus and Jupien, in which the former uses the opportunity to network, to explore with Jupien the erotic potential of the neighborhood. When Charlus asks him about any gay "young society men" who visit the Duc and Duchesse, Jupien tries to describe one but is unable to give a portrait that Charlus recognizes. To the narrator, however, "the portrait seemed an accurate reference to the Duc de Châtellerault" -- the one who seemed to take delight in the embarrassment of the footman serving him at the Duchesse's dinner party.
The incident has obviously put Charlus in a whole new light for the narrator: "Until now, because I had not understood, I had not seen.... an error dispelled lends us an extra sense." He understands the need for concealment, for fear of suffering the fate of Oscar Wilde, "the poet who was yesterday being fêted in every drawing room and applauded in every theater in London, only to be driven on the morrow from every lodging house, unable to find a pillow on which to lay his head." And he launches into a lengthy account of the "freemasonry" of gays that "rests on an identity of tastes, of needs, of habits, of dangers, of apprenticeship, of knowledge, of commerce, and of vocabulary, ... all of them obliged to protect their secret." He also touches on the closeted, the self-denying, the young men ignorant of the meaning of their own desires.
And then he realizes what his recent encounter with Charlus had been.
There were indeed certain individuals that he found it enoiugh to have come to him, and to hold them for a few hours under the sway of his tongue, to appease the desire kindled in him by some encounter.... On occasions, as had no doubt transpired in my own case one the evening when I had been summoned by him after the Guermantes dinner party, assuagement came about thanks to a violent dressing down cast by the Baron into his visitor's face.... M. de Charlus had passed from being the dominated to the dominator, and, feeling himself calmed and purged of his anxiety, dismissed the visitor he had at once ceased to find desirable.Part I ends with the narrator regretting that his voyeurism has perhaps made him miss "the fertilization of the flower by the bumblebee." It's an effective overture to the novel.