When Harry awakes from his night in the hospital wing, his arm is healed and he is eager to tell Ron and Hermione about Dobby and Colin. He runs into Percy, who looks exceptionally happy, and then Harry heads into Moaning Myrtle's bathroom, where he finds his friends. Ron and Hermione have spent the morning concocting the beginning of the Polyjuice Potion, and they listen eagerly to the news about Dobby and the reopening of the Chamber of Secrets. Meanwhile, the entire school is all in a fright about Colin. Ginny Weasley is especially shaken up by the occurrence, and Neville Longbottom, a round and clumsy wizard, has started carrying around protective charms, since he acknowledges fearfully that he is almost a Squib.
In Potions class, Harry distracts Snape by throwing a firecracker into a Slytherin cauldron, splashing swelling potion on the faces of many students, while Hermione sneaks out of the room to procure Polyjuice ingredients from Snape's personal collection. When she returns with the ingredients inside her robes, the swollen faces are back to normal, and Snape is spitting with rage and looking straight at Harry as he threatens expulsion to the troublemaker.
A week later, Harry, Ron, and Hermione spy a poster advertising a new student dueling club, and they go to the meeting to learn to duel. It turns out that Lockhart is heading it, and when he practices his first dueling match, Snape, his opponent, disarms him by crying out, "Expelliarmus!" Lockhart quickly says that he had deliberately allowed Snape to win that one, and he divides the students into pairs, not wanting to lose another duel. Hermione is matched up with a large Slytherin girl named Millicent, and Harry is matched up with Malfoy. The two boys attack each other with all sorts of body-contorting charms, including a tickle-spell and a leg-jerking spell. The two boys are brought to the front of the room to demonstrate for the entire club, and Snape whispers something to Malfoy, who immediately conjures an angry black snake from his wand. Lockhart tries to help, but instead makes the snake angrier and sends it straight for Justin Finch-Fletchley. Without even thinking, Harry calls out at the snake to leave Justin alone, and the snake falls into a docile heap on the floor. Harry is relieved, but the class is terrified, and only after class does he find out through Ron and Hermione that he spoke Parseltongue-snake language-a feat for which Salazar Slytherin himself was famous. Harry begins to question if, in fact, he really could be the heir. Furthermore, he worries about the Sorting Hat's decision to place him into Gryffindor, when it mentioned first that he could be great through Slytherin.
The next day Harry is restless and goes to find Justin to explain what had actually happened, but as he looks for him in the library, he overheard several Hufflepuffs, led by Ernie Macmillan, discussing the probability that Harry was the heir, and that Voldemort had not succeeded in killing him only because the infant Harry already had powerful dark protective powers. Harry speaks to the Hufflepuffs and asks for Justin, and they all react fearfully and with accusations that anger and annoy Harry. As Harry returns to his house through the corridors, he runs into Hagrid, who is holding a dead chicken, and soon after he trips over the stone-hard figure of Justin Finch-Fletchley, lying near the airy floating figure of Nearly-Headless Nick. Soon Peeves the Poltergeist sees the scene and cries out, alerting the students and teachers, all of whom quickly rush into the corridor. Many angry faces glare accusatorily at Harry, and Professor McGonagall calls Harry to come with her. Together they walk to Dumbledore's room.
This chapter includes a great deal of foreshadowing, both of Percy, when he is walking cheerfully through the hallway the morning after Colin has been petrified, and of Ginny, who is unduly upset, and finally of Harry, who when put on the spot reveals himself as a Parselmouth. Nobody has been caught yet, but many people still look suspicious, and everybody is uneasy. The mandrakes are growing and everybody is eager for them to mature and be put to use to restore the petrified folk.
The dueling club meeting serves as a catalyst for the school to suspect Harry, and it is debatable whether Snape instructed Malfoy to conjure a snake simply because it is the Slytherin mascot, or because he wanted to test whether Harry could be the heir by seeing whether he could communicate with snakes. In any case, the students, including Ron and Hermione, are deeply worried by Harry's response to the snake, as we see in the library, when the Hufflepuffs speculate on Harry's dark powers. This scene is horribly unfair, especially when Ernie points out that everybody knows that Harry is a Muggle-hater because he so obviously hates living with the Dursleys. This upsets Harry further because he does hate the Dursleys, but not because they are Muggles. Explaining this brings him no success or sympathy. When he winds up alone in the corridor with the petrified figures of Justin and Nick, the wide-spread suspicion of him is deepened. Recall that in chapter six, Justin told Harry that he was signed up for Eton, a Muggle school, before deciding to go to Hogwarts. If Harry is the Heir of Slytherin, then this information would have helped him to target Justin.