Spring continues its sweep through Hogwarts, but even the loveliness outside the castle cannot take Harry's mind off the terror inside the castle. He ponders Hagrid's advice regarding the spiders and Dumbledore's about help and loyalty, but he is not sure how to proceed with either. Malfoy, meanwhile, seems delighted by the state of things. He boasts that his father has finally gotten Dumbledore out, and he suggests that Snape apply to be the new headmaster.
In Herbology class, Ernie Macmillan apologizes for having suspected Harry, since after the attack on Hermione he now that Harry would never have been responsible for hurting a good friend. Harry accepts the apology, and minutes later during this same class, he spies a line of spiders moving toward the Forbidden Forest. He whacks Ron with his pruning shears, and Ron looks doubtful at the prospect of following them. They head next to Lockhart's defense against the dark arts class, during which a confident Lockhart gleefully waxes on about the safe state of the school now that Hagrid has been removed. Ron and Harry are extremely annoyed, and after the joint events of Lockhart's accusation of Hagrid combined with a glance at Hermione's empty seat, the two agree to follow the spiders that very night.
Beneath the invisibility cloak, Ron and Harry set out into the forest with Fang scampering nearby. They soon spy a few solitary spiders scuttling deep into the forest, away from the paths, and so they follow them for a long time. Eventually, they hear something large moving behind the trees, and they are greatly relieved to see that it is Ron's once-flying car, the Ford Anglia that hit the Whomping Willow and now is running wild in the Forbidden Forest. The boys laugh at their initial fright and prepare to continue when they and Fang are met and captured by a trio of clicking, horse-sized spiders. Ron, who fears spiders above all else, is speechless with fear, and Harry himself is terrified too.
The spiders carry them into a clearing with a giant domed web, where they are met with an elderly blind spider, Aragog, who first dismisses Ron and Harry to be killed, but then speaks with them when they claim to have been sent by Hagrid. The boys learn from Aragog that the school thought he was the monster within the Chamber, but really he had been given to Hagrid as an egg and raised in captivity. They learn also that the monster in the chamber is the creature most feared by spiders, and because of that its name is not spoken. They learn finally that the creature's victim was found in the toilet, and that soon after the event, Hagrid set Aragog free in the Forest. After informing them of this, Aragog instructs his children to eat the humans and dog. For a moment Harry and Ron know that they are doomed, and then all of a sudden they hear a horn and see the Weasley's car rumbling over to them. Panicked, they open the door, shove in Fang and themselves, and flee the Forbidden Forest.
Once they say goodbye to the car and head back up to the dormitory, feeling discouraged at having found no new clues. Only once Harry is back up in his bed does it occur to him that the girl found in the bathroom fifty years back could be Moaning Myrtle.
Harry's role as a suspect finally diminishes in this chapter after Hermione is petrified, because everybody knows that Harry would never harm one of his best friends. The situation is still dire and complicated, however, and the venture into the Forbidden Forest does not make it any less so. Two vital themes are introduced during this venture, each of which addresses the narrative's attitude toward evil adversaries.