During the summer holiday after Harry Potter's first year at Hogwarts School of Witchcraft and Wizardry, the Dursleys have locked away Harry's school equipment. On Harry's twelfth birthday, a house elf called Dobby appears and warns Harry that he will be in mortal danger if he returns to Hogwarts. When Harry insists he will return to the school, Dobby uses magic to sabotage a dinner party hosted by Harry's uncle, Vernon Dursley. The Ministry of Magic sends Harry a letter warning that he risks expulsion if he uses magic outside Hogwarts again. No longer afraid of Harry's magical abilities, Uncle Vernon says Harry cannot return to Hogwarts and fits bars on Harry's window.
Ron Weasley and his older twin brothers Fred and George rescue Harry in a flying car, and take him to spend a pleasant month at their home, The Burrow. Ron's younger sister, Ginny, who is about to start at Hogwarts, develops a crush on Harry. While the children are buying school books in Diagon Alley, Lucius Malfoy, the father of Draco Malfoy and even more arrogant, provokes a fight with Ron's father, Arthur Weasley.
At the start of the school term Harry and the Weasleys go to London King's Cross railway station to catch the Hogwarts Express. Harry and Ron are the last to try to enter Platform 9¾, and the wall between platforms 9 and 10 will not let them through. The boys steal the flying car and fly to Hogwarts. On arriving, they crash into the Whomping Willow, which immediately attacks, damaging the car and breaking Ron's wand. The battered car retreats into the Forbidden Forest. Professor Snape catches the boys sneaking into the Great Hall and tries to have them expelled, but Professor Dumbledore, the headmaster, opposes this.
Harry finds that the new Defence Against the Dark Arts teacher is the celebrity Gilderoy Lockhart, who has required pupils to buy copies of all his books. Lockhart sets them a test consisting entirely of trivia questions about himself, but proves incapable of controlling a group of pixies.
Harry begins to hear a voice that whispers about its desire to kill but is inaudible to others. A message magically written on a wall proclaims, "The Chamber of Secrets has been opened. Enemies of the Heir, beware" - with school caretaker Filch's cat petrified beside it. Persuaded by Hermione Granger, the History of Magic teacher recounts a legend that Salazar Slytherin, one of the school's founders, built a secret chamber in the school, and sealed it so that only his true heir could open it. This would unleash a monster that would kill all pupils whom Slytherin considered unworthy. Harry, Ron and Hermione conclude that the most likely heir of Slytherin is Draco Malfoy, who constantly insults "Mudbloods", pupils from non-magical families. They hatch a plan to disguise themselves as Slytherin House pupils by means of Polyjuice Potion and spy on Draco.
During a Quidditch match Harry's arm is broken by a Bludger that inexplicably targets only him. While in the school's hospital he wakes up to find Dobby tending him. The house elf confesses that he blocked the entrance to Platform 9¾ and bewitched the Bludger, in both cases to exclude Harry from the school. Dobby flees when Dumbledore and Professor McGonagall bring in a younger pupil who has been petrified. Harry hears Dumbledore conclude that the Chamber of Secrets has indeed been opened.
While Harry, Ron and Hermione are making the Polyjuice Potion, a long and complex process, Lockhart sets out to teach the pupils magical duelling. In a duel with Harry, Draco, coached by Snape, conjures a snake. Harry orders it stop threatening a pupil, and it obeys. Ron concludes that Harry is a Parselmouth, in other words he has the very rare talent of conversing with snakes, for which Salazar Slytherin was famous. Rumours that Harry is the Heir of Slytherin spread through the school. After being accused by a group of pupils, Harry finds, lying petrified on the floor of a passage, the student whom the snake threatened and one of the school's ghosts.
Harry and Ron use the Polyjuice Potion to disguise themselves temporarily as Crabbe and Goyle, Draco's muscular but dim sidekicks. Draco, fooled by the disguise, tells them he is not the Heir but wishes he could help him.
A few weeks later Harry and Ron hear a ghost, Moaning Myrtle, in one of the girls' toilets. Myrtle shows them an empty 50 year-old diary which dropped through her out of thin air. One evening Harry starts writing in the diary, which magically produces written replies from "Tom Riddle", who claims to have sealed the Chamber of Secrets when it last opened, 50 years ago. The diary transports Harry's mind back to the Hogwarts of 50 years ago, where Riddle finds 13 year-old Hagrid looking after a huge spider-like creature and accuses him of opening the Chamber.
There are no further petrifications in the next four months, and the rumours about Harry fade away. Then Harry finds that the diary has been stolen, and Ron points out that only a Gryffindor student could have done it, as no-one else would have known the password to open the magical door of their quarters. The following day Hermione and another girl are petrified. Professor McGonagall fears the school will have to be closed to avoid further casualties. Harry and Ron visit Hagrid's house, using the Invisibility Cloak that Harry inherited from his father in order to evade the curfew that has been imposed to keep pupils away from danger. Almost immediately Dumbledore and the Minister for Magic arrive, and the boys hastily take cover again under the Cloak. The Minister announces that, as a precaution, Hagrid is to be imprisoned in Azkaban until the emergency is over. Lucius Malfoy then arrives to announce that the school's governors have suspended Dumbledore from the position of headmaster. On his way out, Hagrid drops a hint to Harry and Ron, who are still concealed, that they should "follow the spiders".
After several days Harry spots some spiders apparently moving towards the Forbidden Forest, and the two boys slip out that night. In the heart of the Forest they are captured by giant spiders, led by Aragog, whom Hagrid had been tending when Riddle accused him of opening the Chamber of Secrets. Aragog explains that he was not the monster of the Chamber, but was imported as an egg, and fled the school after a girl was killed in a toilet. He will not eat the boys but cannot restrain his brood from attacking. Harry and Ron are rescued by the flying car, which has been hiding in the Forest ever since its encounter with the Whomping Willow.
The boys realise that Moaning Myrtle may be the ghost of the girl killed 50 years ago. On the way to the toilet she haunts, they are intercepted by Professor McGonagall, and Harry tells her they are going to visit Hermione, who is still petrified. In the hospital Harry extracts from Hermione's hand a note that leads them to think the monster is a Basilisk and may be emerging via Myrtle's toilet. On their way there they hear that Ginny Weasley has been taken into the Chamber by the monster. The rest of the staff insist that Lockhart is best qualified to handle the situation, and he goes to his rooms "to prepare". Harry and Ron go there to tell him what they have discovered, and find him packing hastily. Lockhart admits that he stole the credit for "his" exploits from other wizards and witches, after wiping their memories. He tries to wipe the boys' memories, but Harry disarms him with a spell. The two march Lockhart to the toilet haunted by Myrtle, who says that, as she died, she saw the monster by a sink. When Harry gives the order "Open!" in Parseltongue (snake speech), the sink moves aside to reveal a passage. In a tunnel under the school, Lockhart steals Ron's wand and tries to memory-wipe the boys. However Ron's wand has been unreliable ever since it was broken, and the spell backfires on Lockhart.
Ron stays to look after Lockhart while Harry moves forward, entering a long chamber, where Ginny lies at the far end, beside the diary. As he examines her, Tom Riddle appears, looking exactly as he did in Harry's vision of 50 years ago, and explains that he is a memory stored in the diary. Ginny started writing about her adolescent hopes and fears, and Riddle won her confidence by appearing sympathetic, draining energy from her in the process, and gained enough strength to make Ginny open the Chamber. Ginny threw away the diary when she realised she was responsible for the attacks, and it later came into Harry's possession. From conversations with Harry via the diary the virtual Riddle learned his own identity – he is the young Voldemort. Dumbledore's pet phoenix, Fawkes, appears and drops a bundle at Harry's feet, as Riddle releases the basilisk slides out. Fawkes blinds the monster, so that its glare is no longer dangerous, and Harry finds that the bundle contains a magnificent sword, with which he kills the basilisk – but only after being bitten by the creature's venomous fangs, one of which breaks off. As Riddle gloats over the dying Harry, Fawkes weeps over the wound and cures him. Harry stabs the diary with the broken fang, and Riddle screams and vanishes.<2> Ginny revives and they return to Ron, who is still watching over the memory-wiped Lockhart.
Fawkes airlifts all four out of the tunnels and then leads them to the office of Professor McGonagall, who has been acting as head of the school. Dumbledore and Mr. and Mrs. Weasley are also there, and Harry tells them the whole story. Dumbledore revokes his threat to expel the boys if they broke more rules, and gives them Special Awards for Services to the School and Gryffindor enough points to win the inter-House competition. When Harry mentions his earlier fears that he was the Heir of Slytherin, Dumbledore says that Harry chose Gryffindor House, and only a true member of that House could have used Godric Gryffindor's sword to kill the basilisk.
Lucius Malfoy bursts in, accompanied by Dobby. Dumbledore says the governors have just reinstated him as head of the school, after hearing of Ginny's abduction. Understanding mimed hints from Dobby, Harry accuses Malfoy of slipping the diary into one of Ginny's books during the fracas in Diagon Alley. As Malfoy leaves with Dobby, Harry slips a sock into the diary and returns the diary to Malfoy. Malfoy throws away the sock in disgust and Dobby catches it - a "giving of clothes" that frees Dobby from servitude to the Malfoys. Enraged at the loss of a servant, Malfoy draws his wand, but Dobby magically knocks down Malfoy, who retreats. All of the basilisk's victims are revived.
<source: Wikipedia>
