Harry Potter, a young wizard, is home from Hogwarts School of Witchcraft and Wizardry for the summer. He lives with his Aunt Petunia, Uncle Vernon, and cousin Dudley Dursley. The Dursleys are what wizards call Muggles, meaning that they have no magical powers. They are afraid of what Harry might do to them, and so restrict him from mentioning the word magic and lock up his messenger owl Hedwig so he can’t send letters to his school friends. Harry is very lonely. This is his twelfth birthday, and everyone seems to have forgotten. He hasn’t heard from his best friends Ron Weasley and Hermione Granger. The Durselys are focused on a dinner party with the Masons they have planned that evening to promote Mr. Dursley's business. Uncle Vernon orders Harry to stay in his room all evening and make no noise. Sitting in the garden glumly, Harry sees two enormous green eyes staring at him from the hedge. After Dudley taunts him, Harry pretends to cast a spell, for which Aunt Petunia punishes him with yard work. Then she feeds him minimally, while she prepares a feast for the Masons, and sends him to his room.
Harry discovers a little creature with bat-like ears and large eyes sitting on his bed, who identifies himself as Dobby the house-elf. Harry realizes that this is who was peering out at him from the hedge that afternoon. When Harry asks Dobby to sit down, the elf wails loudly in gratitude. He has never been asked to sit down by a wizard. While he speaks to Harry he violently and noisily punishes himself for betraying the wizard family he serves. The house-elf must constantly punish himself at home too, but can only leave if his master sets him free. When Harry asks if he can help, Dobby is overwhelmed with appreciation. Dobby has come to protect Harry by warning him not to go to Hogwarts. Harry tries desperately to keep the Dobby quiet. But all of the noise draws mean Uncle Vernon upstairs. Harry manages to hide the elf just in time. Harry discovers that Dobby has been stealing letters from Harry’s friends, hoping to dissuade him from returning to school. Dobby demands that Harry promise not to go back to Hogwarts. When Harry refuses, Dobby runs to the kitchen and levitates Aunt Petunia’s pudding, threatening to drop it. Harry says no, so he drops the pudding with a crash and disappears, disrupting the dinner party. Then an owl delivers a letter to Harry from the Ministry of Magic warning him that as an underage wizard, he is not permitted to perform magic outside of school, mistaking Dobby’s magic for Harry’s. The owl delivers the letter onto Mrs. Mason’s head, causing her to run screaming from the house. The Durselys didn’t know until the letter that Harry wasn’t allowed to perform magic outside of school. They are no longer afraid of him. Enraged, Uncle Vernon imprisons Harry in his room, installing bars on his window and a cat flap through which they feed Harry only cold soup. He sees no means of escape.
After three days of misery, Harry awakens to see his friend Ron Weasley’s face outside of his window. Ron and his brothers, the twins Fred and George, rescue Harry in a car that their father enchanted to fly. They take him home to the Burrow. Mrs. Weasley yells at her sons for stealing the car, pointing out that they could have died, been seen, or caused their father to lose his job. Though angry, she is also kind, feeding everyone a big breakfast. Ron’s sister Ginny appears briefly and then runs away. Ron says that Ginny has been talking about Harry all summer. Mrs. Weasley orders her sons to degnome the garden. Harry joins in. Mr. Weasley returns home from a night of raids in his job in the Misuse of Muggle Artifacts office at the Ministry of Magic. Unlike his wife, he seems pleased that the boys flew his car. Ron shows Harry his room, self-conscious. Harry tells him it's the best house he has ever been in.
Harry enjoys his holiday with the Weasleys at the Burrow. They receive their letters with instructions for the new school year, including a long list of required textbooks by Gilderoy Lockhart. The Weasleys' owl delivers a message from Hermione Granger, who is excited to meet up with them in London to purchase their school supplies in Diagon Alley. Fred and George notice that their older brother Percy has been sending a lot of mysterious letters.
The Weasleys and Harry travel to London via Floo powder, which they throw into their fireplace to teleport them to another destination on the Floo Network. Because this is Harry’s first time traveling via Floo powder, he gets lost, winding up in the unsavory shop Borgin and Burkes in Knockturn Alley. While hiding, Harry sees his school rival Draco Malloy come into the shop with his father. He observes Lucius Malfoy arrange to sell items that would “embarrass” him if the Ministry of Magic raids his house. Malfoy says that there are rumors about a new Muggle Protection Act, likely the work of Authur Weasley. Lucius admonishes his son for getting worse grades than Hermione, who comes from a Muggle family. Harry runs into his friend Hagrid, the Hogwarts gamekeeper, in Knockturn alley, then is reunited with the Weasleys and the Grangers.
Harry and the Weasleys visit Gringotts bank to retrieve wizard money. Goblins lead them via carts running on tracks through underground tunnels to their vaults. Harry feels bad about his wealth, which he inherited from his parents, relative to the Weasleys’ poverty. In the shop Flourish and Blotts in Diagon Alley they discover a crowd waiting to meet Gilderoy Lockhart at his book signing. Lockhart pulls Harry to the front of the line and makes a show of shaking his hand for the photographer. Then he announces that he will be taking up the post of Defense Against the Dark Arts teacher at Hogwarts in the fall. When Lucius Malloy insults his family, Arthur Weasley throws himself at Malfoy, knocking over Ginny’s cauldron and a shelf full of books. Hagrid breaks up the fight, pulling the two men apart. Lucius Malfoy thrusts Ginny’s transfiguration textbook at her, “his eyes glittering with malice.”
When the day arrives to travel to Hogwarts, the Weasleys and Harry rush to King's Cross Station to catch the Hogwarts Express. To get to platform nine and three-quarters, they have to run through the solid barrier dividing platforms nine and ten without being seen disappearing by Muggles. After the rest of the family gets through, Ron and Harry run last towards the barrier. But it remains solid, so they crash into it conspicuously and then miss the train. Ron convinces Harry that they should fly his father’s car to Hogwarts. On the way there, the car’s invisibility booster fails. When they reach Hogwarts castle, they crash into a tree. The tree they hit attacks them back. Ron’s wand breaks. The car moves them to safety then ejects them and their luggage, and finally disappears into the woods. They observe part of the Sorting Ceremony through the window, in which Hogwarts students are assigned one of four houses (Gryffindor, Slytherin, Hufflepuff, or Ravenclaw) by wearing the Sorting Hat.
Professor Severus Snape discovers Harry and Ron and leads them to his office. He shows them a newspaper headline: "FLYING FORD ANGLIA MYSTIFIES MUGGLES” and promises them that they will be expelled. But Professor McGonagall assigns Harry and Ron detention as punishment. Dumbledore warns Harry and Ron that if they break any school rules again, he will have no choice but to expel them. When Hermione learns that Harry and Ron flew the car to school and crashed it into the Whomping Willow she disapproves. But the rest of their fellow students in Gryffindor House cheer their dramatic entrance.
At breakfast the next morning the Weasleys’ ancient owl Errol delivers a Howler to Ron from Mrs. Weasley. She is furious that they stole the car. It was seen and now Mr. Weasley faces an inquiry at work. Harry attends his first day of classes. On his way to Herbology Gilderoy Lockhart pulls Harry aside to talk about crashing the flying car into the tree, which he assumes Harry did to get attention. In the greenhouse, Professor Sprout teaches her students how to repot Mandrakes. The cry of the Mandrake is fatal to anyone who hears it, so they all put on earmuffs. Hermione explains that Mandrakes can restore people who have been transfigured back to their original state. Harry meets fellow student Justin Finch-Fletchly, who says that he almost went to Eton, an upper-class Muggle school. In Transfiguration class with Professor McGonagall, Ron struggles with his broken wand and discovers that Hermione has outlined all of Lockhart’s lessons with hearts. Colin Creevy, a first-year Gryffindor student, approaches Harry in the hall with a camera, star-struck by his fame, wanting his picture and autograph. Professor Lockhart begins his class with a quiz all about himself. Then he causes pandemonium in the classroom by releasing Cornish pixies.
Oliver Wood, Captain of the Gryffindor Quidditch team, wakes Harry up early, eager to begin training. But the Slytherin team shows up on the field with a note of permission from Snape to train their new Seeker, Draco Malfoy. His father Lucius Malfoy has gifted the team the newest broomsticks. When Draco makes fun of the Weasley brothers’ old broomsticks, Hermione defends the Gryffindor team members for succeeding based on talent, instead of buying their way in like Draco. Draco retorts, “No one asked your opinion, you filthy little Mudblood.” which causes an uproar. Ron tries to attack Malfoy, but his broken wand backfires, and hits him in the stomach, causing Ron to belch slugs. Harry and Hermione help Ron to Hagrid’s nearby cottage, where they discuss the meaning of the slur “Mudblood.” Hagrid mentions a recent visit from Ginny Weasley.
That evening Harry spends his time in detention by addressing envelopes for Gilderoy Lockhart. While in Lockhart’s office he hears a venomous voice threatening to kill. Lockhart doesn’t hear the voice. Back in their dorm, Harry tells Ron about the voice, while Ron tells Harry about his detention polishing school awards.
On his way in from Quidditch practice on a rainy morning, Harry commiserates with Nearly Headless Nick. Harry is worried about a rumor that the Slytherin team’s new broomsticks are extremely fast. Nick is upset because Sir Patrick Delaney-Podmore has disqualified him from the Headless Hunt for not having a completely decapitated head. After finding that Harry has tracked in mud, Hogwarts caretaker Filch demands that Harry follow him to his office. They are interrupted by a crash from Peeves the Poltergeist. While Harry waits for Filch to return, he reads mail on Filch’s desk titled “Kwikspell: A Correspondence Course in Beginner’s Magic.” When Filch sees that Harry has read his mail, he is embarrassed and distraught and lets him go without punishment. Grateful when he finds out that Nearly Headless Nick persuaded Peeves to distract Filch, Harry wonders if he can help him in return. Nick asks Harry to attend his deathday party on Halloween and convince Sir Patrick that he finds Nick very frightening.
Harry, Hermione, and Ron go to Nick’s deathday party in the dungeon on Halloween. Hermione tries unsuccessfully to avoid Moaning Myrtle, a ghost who haunts one of the toilets in the girls' bathroom on the first floor. Sir Patrick interrupts Nick’s speech by bursting through the dungeon wall with a team of ghost horses, belittles him and steals the attention of the crowd by playing games with his decapitated head. He is unconvinced by Harry’s claim to find Nick frightening. The three friends leave the party hoping to catch the end of the school feast. On their way up Harry hears the murderous voice that he heard in Lockhart’s office again, sounding like it is moving upward. Following the voice, he runs up the stairs. Ron and Hermione, confused, follow him. When they reach a deserted passage on the third floor, they discover foot-high words written on the wall: “THE CHAMBER OF SECRETS HAS BEEN OPENED. ENEMIES OF THE HEIR, BEWARE.” Harry almost slips on a large puddle of water on the floor. They find Mrs. Norris, Filch’s cat, hanging by her tail. The other students arrive at the corridor from both ends. Draco Malfoy shouts “Enemies of the Heir, beware! You’ll be next, Mudbloods!” Filch accuses Harry of killing his cat.
Dumbledore gathers Filch, Harry, Ron, Hermione, McGonagall, and Snape in Lockhart’s office and examines Mrs. Norris. He tells Filch that she is not dead but petrified. When Filch blames Harry again, Dumbledore replies that the Dark Magic required is too advanced for a second-year student. Filch maintains that Harry did it to threaten him because he knows he is a Squib. Harry replies that he didn’t touch Mrs. Norris, and that he doesn’t know what a Squib is. Snape wants to know why they didn’t join the feast and why they went up to the third-floor corridor. Harry thinks that the truth would sound too far-fetched, so he lies. Dumbledore promises that the Mandrake potion will cure Mrs. Norris once the Mandrakes are fully mature.
Ron explains to Harry that a Squib is a person born to a wizard family, but who has no magical powers. Justin Finch-Fletchly avoids Harry. Ginny Weasley is particularly upset by the death of Mrs. Norris.
In history class, Hermione asks Professor Binns about the Chamber of Secrets. He relates that Hogwarts was founded over a thousand years ago by Godric Gryffindor, Helga Hufflepuff, Rowena Ravenclaw, and Salazar Slytherin. Eventually, a rift developed between Salazar Slytherin and the others. He wanted to limit Hogwarts admissions to children from wizard families because he distrusted Muggle-born students. After a serious argument, Slytherin left the school. Binns says that’s a far as the facts go. The legend of the Chamber of Secrets says that Salazar Slytherin built a hidden chamber in the castle and sealed it so that it could only be opened by his own true heir to unleash the “horror within” and purge the school of everyone unworthy to study magic.
Harry feels uneasy about the legend of the Heir of Slytherin because the Sorting Hat considered placing him in Slytherin House his first year at Hogwarts.
Harry, Ron, and Hermione decide to search for clues in the corridor where the attack occurred. They discover scorch marks on the floor. Hermione notices spiders hurrying to get outside. Ron admits that he is frightened of spiders because of a traumatic childhood experience. Harry remembers that there was a lot of water on the floor the night of the attack and figures it must have been from the nearby girls’ bathroom. They go in to check it out, and wind up talking to Moaning Myrtle, but she is too self-involved to notice anything helpful. Percy Weasley discovers them leaving the bathroom and is furious at them for breaking school rules. He uses his powers as a Prefect to discipline them by taking points from Gryffindor house.
Ron thinks that Draco Malfoy is the Heir of Slytherin; Hermione is skeptical. She proposes that they make Polyjuice potion to transform themselves into three Slytherin students to get into the Slytherin common room and ask Malfoy questions.
Hermione gets Lockhart to sign a note allowing her to check the book with the Polyjuice potion recipe out of the Restricted Section of the library. The three friends barricade themselves in Moaning Myrtle’s out-of-order bathroom. They discover that the Polyjuice potion recipe is very complex. Ron is disgusted by the thought of drinking it. Harry is worried about how much they will have to steal. Hermione becomes angry. She is uncharacteristically willing to break the rules because Squibs and Muggle-Borns, such as herself, are being threatened. Ron and Harry agree to go through with her plan.
During the next Quidditch match, a rogue Bludger tries to knock Harry out of the air while the Slytherins’ superior brooms allow them to rack up points. Fred and George Weasley try to defend Harry from the Bludger. Harry convinces Oliver Wood to let him deal with the Bludger on his own while trying to catch the Golden Snitch. When Harry sees the Snitch hovering inches above Malfoy’s ear, he pauses for a moment, which allows the Bludger to smash into his elbow, breaking his arm. Harry catches the Snitch, winning the game, and then plummets to the ground. In attempting to mend his broken arm bones, Lockhart removes them instead.
In the infirmary, the school nurse Madam Pomfrey gives Harry Skele-gro to regrow his bones and orders his friends to leave so he can rest. Harry wakes up feeling someone sponging his forehead in the dark. It’s Dobby. When Harry asks Dobby why he wears a pillowcase, the elf explains that it’s a mark of his enslavement. He can only be freed if his masters present him with clothes, so they are careful not to pass him even a sock. Harry discovers that Dobby both sealed the barrier to the Hogwarts Express and enchanted the Bludger to injure Harry so he would be sent home. Dobby tells him that terrible things are going to happen, and are perhaps happening already. He explains that Harry’s defeat of Lord Voldemort meant a great deal to the lowest creatures of the wizard world. He insists that he cannot let Harry stay at Hogwarts now that the Chamber of Secrets is open once more. Dumbledore and McGonagall carry what looks like a statue into the infirmary. They explain to Madame Pomfrey that they found Colin Creevey on the stairs, holding his camera, petrified.
The next day, the news that Colin was attacked spreads through the school, creating an atmosphere of suspicion and fear. In Snape’s potions class, Harry lobs a firework into a cauldron, showering the students with Swelling Solution. During the confusion, Hermione slips into Snape’s office and steals ingredients for the Polyjuice potion.
Gilderoy Lockhart initiates a new Dueling Club for Hogwarts students. When he and Snape demonstrate how to duel with their wands, Snape blasts Lockhart backward off the stage, smashing him against the wall. Snape places Harry with Draco in a dueling pair. Although Lockhart instructs them to disarm each other only, their duel escalates. Malfoy conjures a snake, which raises itself, ready to strike Harry. Snape tells Harry that he will get rid of it. But Lockhart interferes, casting a spell that causes the snake to fly ten feet into the air and fall to the floor loudly. When the snake starts to strike Justin Finch-Fletchley, Harry runs forward shouting for it to leave him alone, which it does. Harry grins at Justin, and is surprised to find him angry and scared. Justin storms out of the hall. Snape makes the snake vanish. Harry hears an ominous muttering in the walls.
As Ron and Hermione hurry Harry out of the hall, the other students draw away from him. Harry is bewildered. Ron asks why Harry didn’t tell them that he’s a Parselmouth. Harry doesn’t know what he’s talking about, so Ron explains that it means he can talk to snakes, which is an uncommon gift, and that this is bad. Harry feels angry and misunderstood. He told the snake not to attack Justin. But the other students don’t speak the language, so they assume the opposite. Hermione points out that Salazar Slytherin was known for speaking Parseltongue, so this could mean that Harry is the Heir of Slytherin. Harry lies awake that night worrying that he could be the heir. He isn’t sure because he doesn’t know anything about his father’s family.
The next day Harry goes to look for Justin to explain that he was protecting him from the snake. In the library, he overhears Ernie McMillan argue to other Hufflepuff students that Harry is Slytherin’s heir. Ernie says that Justin is hiding in their dorm from Harry, afraid because he told Harry that he was Muggle-born. Harry confronts Ernie. They argue about what happened at the dueling club.
Harry, furious, runs into Hagrid, who shows him a dead rooster and says it’s the second killed this term. Then Harry trips over Justin Finch-Fletchley lying on the floor, petrified. Nearly Headless Nick floats next to him, oddly black and smokey, as opposed to his usual white transparent appearance. They both look shocked. Harry sees a line of spiders scuttling away from the bodies. When Peeves starts screaming about the attack, students flood into the corridor causing confusion. McGonagall restores order. Ernie points his finger dramatically at Harry, and yells “Caught in the act!”
McGonagall leads Harry up to Dumbledore's office and tells him to wait. Harry discovers the Sorting Hat and puts it on his head. The Sorting Hat says that Harry was difficult to place, but he stands by what he said, that Harry would have done well in Slytherin. Harry grabs the hat off of his head before it can finish, saying “You’re wrong.” To Harry’s shock, he sees a bird burst into flames, then disintegrate into a smoking pile of ash. When Dumbledore enters, he explains that this is Fawkes, his pet phoenix, who regularly burns and is reborn. Harry sees a baby bird in the pile of ash. Hagrid barges into the office to rush to Harry’s defense. Dumbledore stops him, saying he doesn’t think Harry attacked Justin and Nick. After Hagrid leaves, he asks Harry if there’s anything at all he wants to tell him. Harry thinks of all of his troubles and then tells Dumbledore no, there isn’t anything.
The attack on Justin and Nearly Headless Nick sends Hogwarts into a panic. Fred and George make a joke of Harry’s new pariah status. The term ends and many students return home for the holidays. On Christmas morning, Hermione wakes up Harry and Ron early with presents and the news that the Polyjuice potion is ready.
Everyone at Hogwarts enjoys Christmas dinner. Then Harry, Ron, and Hermione execute their Polyjuice potion plan. They leave out drugged chocolate cake for Crabbe and Goyle. When Draco’s two henchmen eat the cake and pass out, Harry and Ron drag them to the closet, pull out their hair, steal their shoes, and then sprint up to Moaning Myrtle’s bathroom.
Hermione, Harry, and Ron each take separate stalls and drink the Polyjuice potion. Harry transforms into Goyle and Ron into Crabbe. Hermione intends to transform into Millicent Blustrode, but says from her stall that she’s not going to join them after all. Harry and Ron sneak down to the Slytherin dungeons and, oddly, find Percy there. In the Slytherin common room, they speak with Draco Malfoy while disguised as Crabbe and Goyle. Draco shows them a newspaper clipping, which he finds funny, that says that Mr. Weasley was fined for enchanting his car. Harry and Ron are disappointed to discover that Draco is not the Heir of Slytherin and doesn’t know who it is, although he says he wishes he did so he could help. Draco does know a bit about the last time the Chamber was opened fifty years before. He says that a Muggle-born student died. And whoever opened the Chamber was caught and expelled. He relays that the Ministry of Magic raided their family manor last week, but didn’t find much because his father’s Dark Arts valuables are hidden under their drawing-room floor.
As they transform back into themselves, Harry and Ron rush back to Myrtle’s bathroom. They find Hermione distraught because she has partially transformed into a cat. She put Micent Blustrode’s cat’s hair into her potion by mistake. Since the potion isn’t supposed to be used for non-human transformations, she has lingering cat characteristics.
Hermione remains in the hospital for several weeks while she recovers. Ron and Harry visit her often. One night when they are walking back from the hospital, they hear Filch furious because someone has flooded the corridor where the attack took place. They go to investigate and find that the water seems like it’s coming from Moaning Myrtle’s bathroom. Myrtle is wailing even louder than usual because someone threw a book at her. When Harry goes to pick up the book, Ron stops him, warning that it could be dangerous, and relates his father’s stories of books that the Ministry of Magic has confiscated. Harry ducks around Ron to pick it up. The book is a fifty-year-old diary with the name T.M. Riddle written inside. Ron recognizes the name as a student who got a special award for services to the school fifty years ago. Filch made Ron polish Riddle’s shield repeatedly in detention. Harry is disappointed to find that the diary is blank. He doesn’t throw the diary away because he feels as though it were a story he wants to finish. The name T.M. Riddle also feels like it means something to him.
Gilderoy Lockhart decides to boost the morale of the school by throwing a Valentine’s Day celebration. This does not go over well with the staff or students. A dwarf dressed as Cupid catches up with Harry in between classes and tries to deliver a musical Valentine. Harry attempts to escape, embarrassed. In the struggle, Harry’s bag rips. His ink bottle smashes, spilling ink over everything. Draco and Percy appear in the commotion. When Harry tries to run, the dwarf knocks him over and sits on him before singing him his Valentine. Draco picks up Riddle’s diary, thinking it’s Harry’s own. Ginny looks from the diary to Harry, looking terrified. Percy demands that Draco hand it over, but Draco continues to taunt Harry with it. Harry pulls out his wand and shouts “Expelliarmus!” The diary shoots out of Draco hands and Ron catches it. Percy admonishes Harry for doing magic in the corridors, but Harry doesn’t care. Draco teases Ginny for giving Harry the Valentine. Ginny covers her face with her hands and runs into class. Harry notices that the diary, which should be covered in ink, looks unblemished.
That evening Harry experiments with the diary. When he drops ink onto the page it shines brightly and then vanishes. He writes “My name is Harry Potter” and the diary replies, “Hello, Harry Potter. My name is Tom Riddle. How did you come by my diary?” Harry and Tom converse through the diary. Riddle reveals that in his fifth year as a Hogwarts student, the Chamber of Secrets was opened and the monster attacked several students, killing one. He says that he caught the person who opened the Chamber, who was then expelled. The headmaster, Professor Dippett, covered up the incident. But he knew it could happen again because the monster lived on, and the one who had the power to release it was not imprisoned.
Harry is able to enter into the diary. He finds himself invisible in Dumbledore’s office, fifty years ago when Armando Dippett was headmaster. Tom Riddle enters. He wants to stay at Hogwarts over the summer holidays rather than returning to a Muggle orphanage. Dippet says that because of the recent attacks, and death of the girl, he can’t allow him to stay at Hogwarts when the term ends. The Ministry of Magic is talking about closing the school. Dippett asks if Riddle knows anything about these attacks. Riddle replies no. Harry recognizes this as the same type of "no" that Harry had given Dumbledore.
When Tom leaves the room, Harry follows him. Riddle runs into a fifty-year-younger Dumbledore, who tells him to hurry to bed. He continues on to the dungeons. When someone creeps along the passage Tom and Harry follow until they hear whispering and a door creaking. Riddle jumps around the corner. Harry steps out and sees a huge boy crouching in front of an open door with a large box. Tom addresses the boy as Rubeus and tells him that he will have to turn him in. He says that he doesn’t think that he meant to kill anyone, but that monsters don’t make good pets. Rubeus replies that it never killed anyone. Riddle draws out his wand and casts a spell that fills the corridor with light and forces the door open, throwing Rubeus against the wall. A large monster comes out, horrifying Harry and knocking down Riddle. When Riddle tries again, Rubeus leaps on him and seizes his wand. Harry falls out of the scene and back onto his bed with a crash. He tells Ron that Hagrid opened the Chamber of Secrets fifty years ago.
Harry, Ron, and Hermione decide not to say anything to Hagrid unless there is another attack. Neville Longbottom discovers that someone ransacked Harry’s things. Harry realizes that Riddle’s diary is gone.
On his way to a Quidditch match, Harry hears the mysterious murderous voice again. Ron and Hermione can’t hear it. Hermione exclaims that she has just understood something, and runs away to the library. Harry is just mounting his broom when McGonagall cancels the match. She leads Harry and Ron to the infirmary, explaining that there has been another double attack: Penelope, a girl from Ravenclaw house, and Hermione. They were found near the library with a small circular mirror on the floor next to them. McGonagall escorts them back to Gryffindor Tower. She addresses the students, reading new restrictions: All students must return to their house common rooms by six PM, and cannot leave their dorms after that. Teachers will escort students to classes and the bathroom. Quidditch training and matches are postponed. All evening activities are canceled. She adds that it is likely that Hogwarts will be closed unless the culprit behind the attacks is caught and urges anyone who thinks they might know anything to come forward. Some Gryffindor students argue that the teachers should expel all students from Slytherin house, as the obvious source of the attacks.
Harry and Ron decide that it’s time to visit Hagrid. That night they wrap themselves in the invisibility cloak that Harry inherited from his father. Hagrid opens the door with a crossbow. Surprised to see them, he starts to make tea, but is clearly flustered. When there’s a knock at the door, Harry and Ron hide under the invisibility cloak in the corner. Dumbledore enters with Cornelius Fudge, the Minister of Magic. Fudge is there to arrest Hagrid. He says that with four attacks on Muggle-borns, the Ministry has to act. Hagrid protests. Dumbledore tells Fudge that Hagrid has his full confidence. Fudge replies that Hagrid’s record is against him. The school governors have been in touch. He has to take him to Azkaban, the wizard prison, as a precaution. Then Lucius Malfoy enters the cottage with an Order of Suspension for Dumbledore that all twelve governors have signed. Fudge looks alarmed and says suspending Dumbledore is the last thing they want right now. Malfoy replies that the appointment and suspension of the Headmaster is a matter for the governors, and that Dumbledore has failed to stop the attacks. Dumbledore agrees to step aside, but adds “However, you will find that I will only have truly left this school when none here are loyal to me. You will also find that help will always be given at Hogwarts to those who ask for it.” Harry feels that Dumbledore knows they are there and is addressing them. Hagrid also says loudly, “If anyone wanted to find out some stuff, all they’d have ter do would be ter follow the spiders.”
With Dumbledore gone, Hogwarts becomes even more fearful. Draco Malfoy is the only one who enjoys the atmosphere of terror and suspicion. In Potions he says, "I'm quite surprised the Mudbloods haven't all packed their bags by now...Bet you five Galleons the next one dies. Pity it wasn't Granger —." During Herbology class, Ernie apologizes to Harry for suspecting him. He says that he knows Harry would never attack Hermione. When Ernie speculates that Draco Malfoy might by Slytherin’s Heir, Harry replies with a firm no. Harry spots spiders scuttling towards the Forbidden Forest. In Defense Against the Dark Arts class, Lockhart is inappropriately upbeat, convinced that Hagrid must be guilty since he was arrested.
That night Harry and Ron throw on the invisibility cloak and head to Hagrid’s cottage. Along with Fang, they follow the spiders along the path into the Forbidden Forest. They hear something big and see a bright light. Ron realizes that it’s his father’s enchanted car. Then they are suddenly seized from behind by gigantic hairy spiders who carry them to a hollow filled with more spiders, and they release them in front of a web in the center. Aragog, an old blind spider the size of an elephant, emerges to meet them. They learn that Hagrid raised him from an egg in a cupboard in the castle. Aragog remembers that years ago, people at the school mistakenly believed that he was the monster in the Chamber of Secrets and that Hagrid was the Heir of Slytherin. When they blamed him for the death of the girl, Hagrid hid Aragog in the forest. The actual monster in the Chamber of Secrets is so frightening to spiders that they don’t speak its name.
Aragog commanded his children not to harm Hagrid, but he says he will not deny them the fresh meat of Harry, Ron, and Fang. As the spiders surround them, Mr. Weasley’s car comes to the rescue, speeding them out of the hollow and then dropping them on the edge of the forest before it disappears.
Harry realizes that the girl who died, who Aragog said was found in the bathroom, could be Moaning Myrtle.
To the students' shock, Professor McGonagall announces that exams will take place as usual at the beginning of June. A few days before exams, Professor Sprout informs the school that the Mandrakes will be able to revive the petrified students that night. Everyone is hopeful that the petrified students will be able to identify their attacker.
A nervous Ginny Weasley sits with Ron and Harry at the Gryffindor table and says that she has to tell them something. But before she can finish, Percy interrupts them. When Ron yells at his brother, Percy becomes uncomfortable and says that Ginny’s information had nothing to do with the Chamber of Secrets. She walked in on him doing something, but he refuses to talk about it.
Harry and Ron try to sneak into Moaning Myrtle’s bathroom by manipulating Gilderoy Lockhart, but McGonagall catches them. Harry makes up a story that they were going to sneak into the infirmary to tell Hermione that the Mandrakes are almost ready. Moved, she lets them go. In the infirmary, Harry notices that Hermione has something clutched in her hand: a page torn from an old library book with a description of the Basilisk, King of Serpents. They learn that the snake, in addition to venomous fangs, has a murderous stare. Spiders flee before it. The crowing of the rooster is fatal to it. Underneath the passage, Hermione has scrawled the word Pipes.
Harry realizes that the monster in the Chamber of Secrets is a basilisk. He can understand what the serpent is saying because he speaks Parseltongue. The petrified students each looked at the basilisk indirectly, and so avoided its direct death stare: Colin saw it through his camera, Justin through Nick, Hermiuone and Penelope in the mirror, and Mrs. Norris in the reflection in the water. The Heir of Slytherin must have killed Hagrid’s roosters to protect the basilisk. Aragaog’s fear of the basilisk also fits with the description. The serpent must be traveling around Hogwarts in the pipes, which is why Harry has been hearing its voice in the walls. Ron and Harry figure that the entrance to the Chamber of Secrets could be in Moaning Myrtle’s bathroom.
Ron and Harry decide to go to the staff room to tell Professor McGonagall about their discovery. McGonagall orders all students to return to their dormitories, and teachers to the staff room, immediately. Hiding in the wardrobe, Ron and Harry hear McGonagall tell the staff that the monster has taken Ginny Weasley into the Chamber of Secrets. The Heir of Slytherin has left another message on the wall: “Her skeleton will lie in the Chamber forever.” Lockhart joins the staff, who insist that he go battle the monster in the Chamber that night, since that’s what he has been boasting he wants to do. With Lockhart out of the way, they plan to send the students home the next day and close down the school.
In the Gryffindor Common Room, Ron remembers that Ginny tried to speak with them at breakfast. He figures that she must have been taken because she knew something. Harry and Ron decide to tell Lockhart everything. When they go to his office they discover that he is packing up to flee. Lockhart is a fraud: He took credit in his books for the brave actions of others and got away with it by erasing their memories. Lockhart tries to put a Memory Charm on Harry and Ron, but Harry disarms him and Ron throws his wand out the window.
Harry forces Lockhart to join them in Moaning Myrtle’s bathroom. Then Harry asks Myrtle how she died. She says that she saw a pair of big yellow eyes near the sink across from her. They find an image of a tiny snake scratched on the side of a tap. When Harry speaks Parseltongue, the sink disappears, exposing a large pipe. Harry, Ron, and Lockhart go down the pipe, landing in a tunnel covered in small animal bones. They discover an enormous snakeskin. Lockhart tackles Ron and steals his wand. He starts to erase Harry and Ron’s memory, but Ron’s wand backfires, hitting him with the Memory Charm instead. The blast also knocks down a portion of the ceiling, dividing the tunnel. Ron and Lockhart are on one side of a wall of broken rock, while Harry is on the other, Chamber side. Harry continues on while Ron works to clear a passage in the rocks. When Harry finds a wall with a carving of intertwined serpents, he says “Open” in Parseltongue, which opens the Chamber of Secrets.
The Chamber contains columns in the shape of snakes and a huge statue of Salazar Slytherin. Harry finds Ginny at the base of the statue. She is still alive but he can’t wake her. Tom Riddle is leaning against a pillar, watching him. Riddle is blurred around the edges. When Harry asks him if he is a ghost he replies that he is a memory, preserved in his diary for fifty years. Harry asks Tom for his help getting Ginny out of the Chamber, but he doesn’t respond. Harry tries to lift Ginny while Riddle picks up Harry’s wand. Riddle says that he has been waiting to speak with Harry. It dawns on Harry that Riddle is not the friend he thought he was. Riddle explains that Ginny has been writing in his diary for months, telling him all of her worries, including about her crush on Harry. Riddle wrote back sympathetically. As Ginny poured her soul into him, he grew stronger and started to pour his soul into her. Under the power of Riddle, Ginny opened the Chamber of Secrets, strangled the roosters, and wrote the messages on the walls. She didn’t know what she was doing at first, then thinks that she is going mad and attacks everyone.
Harry is horrified and furious. Riddle explains that Ginny finally stopped trusting her diary and tried to dispose of it. Then, to Riddle’s delight, Harry found it. Ginny told Riddle all about Harry’s history, so Riddle wanted to meet Harry. Riddle showed him his capture of Hagrid to gain Harry’s trust. Harry accuses Riddle of framing Hagrid. Riddle says that it was his word against Hagrid’s. Dippett believed him, but Dumbledore didn’t. Dumbledore persuaded the headmaster to train Hagrid as gamekeeper. Since Dumbledore kept a close watch on Riddle, he knew that it wasn’t safe to open the Chamber of Secrets again as a student. But he left behind a diary, preserving his sixteen-year-old self in its pages, so that one day he would be able to lead someone to release Slytherin’s beast.
But Riddle says that killing Mudbloods doesn’t matter to him anymore. His new target is Harry. Ginny stole back the diary before Riddle could get closer to Harry. So he used Ginny to bait Harry into the Chamber of Secrets. Riddle wants to know how it is that Harry managed to defeat Lord Voldemort, who he calls the greatest wizard in the world. When Harry asks why he cares, Riddle uses Harry’s wand to write his name in the air: TOM MARVOLO RIDDLE. Then he waves the wand, and the letters rearrange themselves to: I AM LORD VOLDEMORT. Harry tells him that he isn’t the greatest wizard, Dumbledore is. Then he hears music—it’s Fawkes the phoenix, singing and carrying the Sorting Hat. Riddle laughs at what Dumbledore sent as reinforcements. Harry doesn’t care. Harry tells Riddle that no one knows why Riddle lost his powers when he attacked Harry. But Harry knows why he wasn’t able to kill him: Because Harry’s Muggle-born mother died to save him. Riddle interprets this to mean that Harry was just lucky.
Riddle calls in the basilisk to kill Harry Potter. While Harry runs, Fawkes punctures the snake’s eyes. Harry puts the Sorting Hat on and asks for help. A silver sword lands on his head. As the basilisk strikes Harry, he drives the sword into the serpent’s mouth, killing it. But it’s too late, the serpent’s fang has sunk into his arm, poisoning him. Harry wrenches the fang out as the pain spreads. Riddle gloats as Harry lays dying. Harry senses Fawkes near him and expresses his gratitude. The phoenix lays his head on Harry’s wound and cries. The tears heal Harry, reviving him. As Riddle raises his wand to kill Harry, Fawkes drops the diary into Harry’s lap. Harry seizes the basilisk fang and plunges it into the book. Riddle disappears, screaming. Ginny wakes up. They leave the Chamber, and are reunited with Ron, who is ecstatic to see his sister, and Lockhart, who has lost his memory. They all join hands, as Harry grips Fawke’s tail feathers. The phoenix flies them through the pipe back up to Moaning Myrtle’s bathroom.
They head to Professor McGonagall's office, where they find her along with Dumbledore and Mr. and Mrs. Weasley, who throw their arms around their daughter. Harry places the Sorting Hat and the sword on McGonagall's desk then relates the story of how they figured out that the entrance to the Chamber of Secrets is in Myrtle’s bathroom. McGonagall points out that they broke a hundred school rules, and wants to know how they got out of the Chamber alive. Harry then tells them about Fawke’s timely arrival and the Sorting Hat giving him the sword. He hesitates to implicate Ginny, but Dumbledore understands that Voldemort enchanted her, and just wants to know how. Harry explains that it was the diary. Mr. Weasley is stunned that Voldemort manipulated his daughter. Ginny says sobbing that she found it inside one of the books her mom got her. Dumbledore sends Ginny to the infirmary and asks McGonagall to alert the kitchens to prepare a feast. Ron explains about Lockhart’s ironic amnesia, so Dumbledore asks him to take Lockhart to the hospital as well.
When they are alone, Harry confesses his self-doubts to Dumbledore. He is worried that he is like Riddle. The Sorting Hat considered placing him in Slytherin House. And his fellow students thought Harry was Slytherin’s Heir because he can speak Parseltongue. Dumbledore explains that Voldemort transferred some of his powers to Harry unintentionally the night he gave Harry the scar. Dumbledore reassures him that he belongs in Gryffindor because he chose to be there, declaring that “it is our choices, Harry, that show what we truly are, far more than our abilities.” He offers proof that Harry belongs in Gryffindor: The sword he pulled from the Sorting Hat belonged to Godric Gryffindor.
A furious Lucius Malfoy appears in McGonagall's office, with Dobby cowering behind him, and demands to know why Dumbledore has returned to Hogwarts. Dumbledore tells him that the other governors contacted him when they heard that Ginny Weasley had been taken into the Chamber, asking him to come back. They also related that Malfoy had threatened to curse their families if they hadn’t agreed to suspend him. Dumbledore shows Malfoy the diary and points out that if Harry and Ron hadn’t found it, Ginny might have taken the blame for attacking Muggle-borns, which would have reflected badly on her father, and possibly derailed his Muggle Protection Act. Harry realizes through signals from Dobby that Malfoy planted Riddle’s diary in Ginny’s Transfiguration textbook at Flourish and Blotts. When he accuses him, Malfoy demands that he prove it. Dumbledore says that no one will be able to do that, but he warns him not to try anything like this again.
As Lucius Malfoy and Dobby leave, Harry gets an idea. He asks Dumbledore if he can give the diary back to Malfoy. Dumbledore hands it to him. Harry rushes down the corridor after them, stuffing the diary into one of his own filthy socks along the way. When he catches up with Malfoy and Dobby, he forces the sock-covered diary into Malfoy’s hand. As Malfoy disgards the sock in disgust Dobby catches it. This sets the elf free, because his Master gave him a piece of clothing. Lucius pulls his wand on Harry, but Dobby protects him. Weeping, Dobby thanks Harry for freeing him, and then disappears with a loud crack.
Hogwarts celebrates with an all-night feast. All of the petrified students are revived. Hermione is thrilled that Harry figured out the mystery. Ron and Harry secure the House Cup for Gryffindor. Exams are cancelled. Hagrid has been released from prison. Lockhart leaves to regain his memory. Lucius Malfoy loses his position as governor. Harry, Ron, Hermione, Fred, George, and Ginny travel together on the Hogwarts Express. Ginny reveals that Percy’s mysterious behavior was because he has a girlfriend: Penelope Clearwater, the Ravenclaw Prefect who was petrified with Hermione. She caught them kissing. Harry writes his telephone number down for Ron and Hermione. Hermione assumes that Harry’s aunt and uncle will be proud of Harry’s accomplishments. He jokes that they will be furious that he didn’t die. They return to the Muggle world.