Because the setting is so unique in this novel, much of the Initial Situation consists of dunking the reader into this very different environment. There's a reason Huxley spends three chapters bringing us up to speed on what's happened in the last 600 years or so, and we conveniently get a detailed vision of the novel's present in the meantime. As far as the new reader knows at this point, Bernard is the protagonist. The central conflict for both him and Helmholtz is melancholy or mild discontent. Bernard's love for Lenina is also part of this stage, since as far as we can tell things have been this way for a while.
On the Lenina front, Bernard has finally asked her out, only to find that she's as dull as any other programmed citizen. More importantly, however, is the impending threat to life as he knows it, starting right about the time that Helmholtz reveals Bernard's impending exile to Iceland. Conflict, Part Deux, begins when Bernard decides it would be a good idea to bring John back to the civilized world. We're pretty sure this spells trouble, especially because there's another hundred pages or so to go. Also, John starts falling in love with Lenina, which for a Shakespeare-quoting man cannot go well.
Everything went downhill pretty fast. But to be fair, we could see it coming. John's incompatibility with "civilization" was clear from the start, so it was only a matter of time before his chastity clashed with Lenina's promiscuity, his self-denial with soma, and his love of Shakespeare with the feelies. The major complication scene drags out over Chapters Seventeen and Eighteen, where John and Mustapha can finally clash in person. It doesn't get much more complicated than a philosophical treatise pretending to be a novel. (Talk about a wolf in sheep's clothing.)
We're pretty sure an S&M mass-orgy is as climactic as it gets.
We don't exactly know what happened with John. We're not sure if he had sex with Lenina during the mass-orgy, and for a few moments we're not even sure what happened in the big scene at all.
Not much can happen once the protagonist has died, so we're definitely in denouement land here. It's kind of a weak version of this stage, but let's face it: we're all still feeling overwhelmed from that climax.
An interpretation for this conclusion is subject to debate. What is going on with these hanging feet? Check out the imagery Huxley uses. The feet, he says, are like "unhurried compass needles." Does a compass hint at technology? Maybe. Is there something to be said about that? It's possible. You've also got the very precise listing of directions: "north, north-east, east, south-east, south, south-south-west" etc., which actually reminds us of the 33 centimeters per hour bit in Chapter One – it's the horror of scientific precision all over again. There's also a sense of rhythm here, with the feet turning one way and then the other, and rhythm is big in Brave New World. So while we can't say definitively what the conclusion is to Brave New World, and what the image of John's dead, hanging body has to do with it, we can at least get a sense of the larger, thematic points it addresses.