Harry Potter and the Chamber of Secrets recap

In his second year, Harry is warned by a house-elf, Dobby, to stay away from Hogwarts, then finds the school terrorized by an unknown monster. A message on a wall announces that the Chamber of Secrets has been opened, and students begin turning up Petrified, all of them of non-magical descent. Harry discovers he can speak to snakes, which turns suspicion on him, and the school fears he is the culprit. Following the trail through an enchanted diary that shows a false memory, and past spiders and clues, Harry and Ron learn the monster is a giant serpent, a basilisk, moving through the castle's pipes, and that Ron's sister Ginny has been taken into the Chamber. Harry descends alone, confronts a memory of the young Tom Riddle, who is revealed to be Voldemort's teenage self, kills the basilisk with a sword, and destroys the diary, saving Ginny. Dobby is freed and Voldemort's plan through the diary is undone.

Harry Potter is an orphan who was raised by his cruel aunt and uncle, the Dursleys, and learned at eleven that he is a wizard, famous for surviving the attack in which the dark wizard Lord Voldemort killed his parents. At Hogwarts School of Witchcraft and Wizardry he was sorted into Gryffindor House and made his first true friends, the loyal Ron Weasley and the brilliant, bookish Hermione Granger. In his first year he uncovered a plot to steal the Philosopher's Stone, a source of immortality, and found that the timid teacher Quirrell had been sheltering the weakened, bodiless Voldemort. Harry stopped the theft, protected by the sacrifice his mother made in dying for him, and the Stone was destroyed. Voldemort survived, powerless and in hiding, and Dumbledore, the school's headmaster, warned that he would one day try to return.

Harry endures a wretched summer with the Dursleys until a house-elf named Dobby appears in his bedroom and begs him not to return to Hogwarts, warning of a deadly plot; when Harry refuses, Dobby sabotages him to try to force him home, nearly getting him expelled. Ron and his twin brothers rescue Harry in their father's enchanted flying car and take him to the Weasleys' ramshackle home, the Burrow. On the crowded shopping trip to Diagon Alley, Harry meets the vain celebrity author Gilderoy Lockhart, the new Defence teacher, and clashes with Draco Malfoy and his cold, sneering father, Lucius, who despises the Weasleys and everything they stand for. When the boys are unable to reach the hidden platform to catch the school train, they take the flying car to Hogwarts instead, crashing it spectacularly and drawing the fury of the Potions master, Snape.

Settling into a second year of lessons made ridiculous by Lockhart's showing off, Harry begins to hear a cold, murderous voice moving through the castle walls that no one else can hear. On Halloween the caretaker's cat is found Petrified beneath a message daubed on the wall: the Chamber of Secrets has been opened, and its enemies should beware. According to legend the Chamber was built centuries earlier by one of the school's founders, Salazar Slytherin, who wanted to purge Hogwarts of students without pure wizarding blood, and it hides a monster only his heir can control. Suspicion and fear spread through the school. Harry, Ron, and Hermione begin to investigate, and their attention drifts toward Draco Malfoy as a likely heir, though they have no proof.

The attacks continue and more students, all of non-magical descent, are found Petrified. At a duelling club Harry accidentally reveals that he can speak to snakes, a rare ability strongly associated with Slytherin and dark magic, and the school turns against him, many now convinced he is the heir opening the Chamber. Hoping to catch the culprit, the trio brew a difficult potion to disguise Ron and Harry as Draco's friends and question him, only to learn he knows nothing about who is behind the attacks. Meanwhile Harry finds an old, blank diary that once belonged to a student named Tom Riddle. When Harry writes in it, Riddle writes back and shows him a memory in which, fifty years earlier, Riddle accused the boy Hagrid of opening the Chamber and keeping a dangerous creature, getting him expelled.

The diary is stolen from Harry's dormitory, and soon afterward Hermione is Petrified. Before she was struck she left the trio a vital clue: the monster in the Chamber is a basilisk, a giant serpent whose direct gaze kills and whose reflected or indirect gaze only Petrifies, and it has been travelling unseen through the castle's plumbing. That explains why no victim has died and why Harry alone could hear it, since he can understand snakes. With the school on the edge of closing, Ginny Weasley is taken down into the Chamber itself, and a new message warns that she will die there. Harry and Ron force the reluctant Lockhart to come with them and find the entrance in a girls' bathroom, opening it with the snake-speech Harry did not know he was using.

In the tunnels Lockhart tries to flee and wipe the boys' memories, but his stolen wand backfires and erases his own, and a cave-in separates Harry from Ron. Harry goes on alone and finds Ginny unconscious, her life draining away, watched over by the memory of Tom Riddle, who has stepped out of the diary. Riddle reveals that he is the young Lord Voldemort, that he framed Hagrid years ago, and that he has used the diary to possess Ginny and reopen the Chamber. He sets the basilisk on Harry. Fawkes, Dumbledore's phoenix, blinds the serpent and brings Harry the Sorting Hat, from which Harry draws a sword and kills the basilisk, taking a fatal bite that Fawkes's tears then heal. Harry stabs the diary with a basilisk fang, destroying Riddle and reviving Ginny. Above ground, Lucius Malfoy is exposed as the one who planted the diary; Harry frees the Malfoys' house-elf, Dobby; the Petrified students are cured; and Hagrid is cleared and Dumbledore reinstated.

Harry reaches the Chamber of Secrets and finds Ginny Weasley near death, her life being drained into an enchanted diary. The diary preserved a memory of Tom Riddle, a former Hogwarts student who grew up to become Lord Voldemort; he had used the book to possess Ginny and reopen the Chamber, setting a giant basilisk to attack Muggle-born students. With help from Dumbledore's phoenix, Fawkes, and a sword produced by the Sorting Hat, Harry kills the basilisk, though its fang pierces him; Fawkes's tears heal the wound. Harry stabs the diary with the fang, destroying Riddle's memory and saving Ginny. It emerges that Lucius Malfoy had slipped the diary among Ginny's things to discredit the Weasleys and Dumbledore. Harry tricks Lucius into freeing his mistreated house-elf, Dobby, who is now devoted to Harry. The Petrified students are cured, Hagrid is cleared and released, and Dumbledore is restored as headmaster. Harry ends the year having faced Voldemort's past self and won, though the encounter has left him uneasy about how alike the two of them can seem.