Harry Potter and the Chamber of Secrets is the story of the titular hero's second year attending Hogwarts School of Witchcraft and Wizardry. Amidst a series of mysterious attacks on the student body Harry must cope with the suspicions of his fellow students, the school's mysterious past, and the identity of the force behind the attacks. The story is an illustration of childhood friendship, the shadows of past sins, and the perils of false accusations in climates of paranoia.
While the Dursley family—his uncle Vernon, aunt Petunia, and cousin Dudley—entertain a potential client for Vernon’s drill-manufacturing company Grunnings, Harry Potter reminisces upon the events of the previous year, including his enrollment in Hogwarts School of Witchcraft and Wizardry and confrontation with Lord Voldemort (the Dark wizard whose reign seemingly ended when he killed Harry’s parents and attempted but failed to kill Harry himself), and laments the fact that the best friends he made at the institution have not written to him, even for his birthday, on which the novel opens.
Just as Harry is starting to anticipate his return to Hogwarts School, an impish house-elf named Dobby arrives out of nowhere to warn Harry against the decision to return to the wizarding world, citing grave danger as the reason and inciting Harry’s gravest punishment yet when he smashes a dessert crafted by Petunia for the dinner party and frames it on Harry himself. Ron Weasley arrives with his twin brothers Fred and George to perform a jailbreak in their father Arthur’s enchanted Ford Anglia and to deposit him at their family home theBurrow for the remainder of his holidays. Harry and the rest of the Weasleys—mother Molly, third eldest son Percy, and daughter Ginny—travel to Diagon Alley, where they are reunited with Hermione Granger and introduced to Lucius Malfoy, father of Harry’s school nemesis Draco, and Gilderoy Lockhart, a conceited autobiographer who has been appointed Defense Against the Dark Arts professor. As Harry and Ron plan to depart with the rest for Hogwarts School, the barrier within King’s Cross station that separates Muggles from wizards refuses to allow them passage, forcing them to fly Arthur’s car to the school, where they crash into a sentient willow tree on the grounds.
The crash lands them in hot water with headmaster Albus Dumbledore and Minerva McGonagall, Head of Gryffindor House and the Transfiguration professor, who doesn’t expel them in spite of the clear breach of magical law but does assign them to detentions: Ron must clean the school trophies in the trophy room, and Harry must help the lunatic Professor Lockhart with addressing his fan mail. Lockhart’s classes turn out to be as obsessed with the man as he is with himself, as proven by a “hands-on” training experience with a pack of destructive pixies (small, bluish creatures that exist to cause mayhem), and Harry learns that prejudice exists in the wizarding world by the way of blood status: Those with “pure” blood (only wizarding heritage) have the advantage over and condescend to those with Muggle parentage. Harry also begins hearing an unnerving voice (one only he can hear) seemingly coming from the walls of the school itself, and during a “death-day party” for the Gryffindor ghost, the trio happens upon a petrified Mrs. Norris, the cat belonging to school caretaker Argus Filch, and a warning scrawled across one of the walls: “The chamber has been opened. Enemies of the heir, beware.”
Rumours fly around the school regarding the history of the Chamber of Secrets, and for Harry and his friends, the answer comes by way of Cuthbert Binns, the ghostly professor of History of Magic: The Chamber of Secrets, which houses a terrible monster, was created by one of the school’s founders, Salazar Slytherin, after a fundamental disenfranchisement with the others (Godric Gryffindor, Helga Hufflepuff, and Rowena Ravenclaw), believing that students of non-magical parentage should be refused entry to the school. When a Bludger, one of the balls involved in Quidditch, chasesafter Harry instead of zigzagging toward any player it can hit, breaking his arm, Dobby returns in the middle of the night to visit Harry in the hospital wing, revealing that it was he who charmed the Bludger and sealed the gateway at King’s Cross and that the Chamber of Secrets had been opened before. Another attack occurs, this time to a first-year Gryffindor named Colin Creevey who idolizes Harry, and the school enters panic mode, setting up a dueling class for the students (led by Lockhart and Potions master/Head of Slytherin House Severus Snape), during which it is revealed that Harrycan speak to snakes.
This sparks the rumour mill yet again, as students around the school suspect Harry of being the Heir of Slytherin, and circumstantial evidence to support this theory arrives in the form of another attack, this time on Hufflepuff second-year Justin Finch Fletchley and the Gryffindor ghost. Harry, Ron, and Hermione begin to suspect that Draco is behind the attacks, given his family history of remaining well within Slytherin ranks and open hostility toward Muggle-born students, and so Hermione concocts Polyjuice potion, which allows them to become Draco’s boorish lackeys, Vincent Crabbe and Gregory Goyle, for an hour to interrogate him. This comes to nothing, as Draco’s father only told his son the general facts of the previous opening of the Chamber and that it occurred fifty years previously. Meanwhile, Myrtle Warren, an existentially mopeyghost that haunts a bathroom, unwittingly provides a new clue in the form of a diary deposited in her stall—a diary, moreover, that belonged to Tom Riddle, a student who knows all too well about the Chamber, having been witness to a fellow student’s death fifty years ago. The culprit, he revealsto Harry, was none other than Rubeus Hagrid, now gamekeeper for Hogwarts School; when Hermione is attacked next, alongside a Ravenclaw prefect, the school is put on lockdown, and Dumbledore and Hagrid are forced to leave the premises.
Fortunately for Harry and Ron, Hagrid left a set of instructions: to follow the spiders currently fleeing into the Forbidden Forest, which they do, only to find the monster blamed for the attacks fifty years before, a massive spider named Aragog, who explains to the duo that the real monster is one that spiders fear above all others. Hermione provides the last set of clues that inform them of the monster’s identity: It is a basilisk, which is a giant serpent (hence Harry’s ability to understand it) that kills with a stare (although no one is dead because of various devices through which they indirectly saw the monster) and which spiders (such as Aragog and his offspring) fear above all others.Harry figures out from hints Aragog dropped that a student who died during the previous attacks is Myrtle, and when Ginny is apparently taken by the monster into the Chamber, they discover that the entrance is in the bathroom they’ve been using to make Polyjuice Potion. Harry, Ron, and Lockhart enter the Chamber, but the dunderheaded professor (who reveals that he’s a fraud) causes a rockfall upon attempt to modify the boys’ memories with Ron’s damaged wand, and Harry must enter alone. He arrives to find Ginny in a weakened state being watched over by a shadowy, ghostly Riddle, who explains that he is the boy who will become Voldemort in the future before setting the basilisk upon Harry; Harry defeats the monster and destroys the diary, which makes Riddle disappear.
Harry, Ron, Ginny, and Lockhart return to the main castle and reunite with McGonagall, Dumbledore, and Mr. and Mrs. Weasley. Ginny, whose entrancement by Voldemort caused all of the petrification and troubles over the course of the year, is given a reprieve by Dumbledore, who reasons that greater wizards have been duped by Voldemort before and takes great interest in the qualities of the diary, which Harry gives to him. Lucius Malfoy bursts in after this meeting, demanding to know why and how Dumbledore has returned to the school and accompanied by Dobby, revealing the family to whom he is enslaved. The house-elf also provides Harry with unspoken cues regarding the diary’s ownership: While it was Tom Riddle’s, it had been in the Malfoys’ possession, and Harry returns it, devising a scenario involving his own sock that frees Dobby from the Malfoys’ employment. The petrified students are cured, the end-of-year exams are cancelled (much to Hermione’s chagrin), Hagrid comes back in the middle of the final feast, and Harry returns to Privet Drive in higher spirits than he last left it.