Harry Potter and the Chamber of Secrets

While Harry Potter spends the summer with the Dursleys, Dobby, a house-elf, warns Harry of an "impending danger" at Hogwarts. He attempts to prevent him returning to Hogwarts by sabotaging an important dinner with Vernon Dursley's client. Vernon tries to prevent his departure in retaliation, but his friend Ron Weasley and his brothers Fred and George rescue him in their father's flying car. Harry meets up with Hermione Granger in Diagon Alley, where they meet Hogwarts' new Defence Against the Dark Arts teacher, Gilderoy Lockhart, along with Draco Malfoy and his father, Lucius, who Harry sees slip a book into Ginny Weasley's cauldron.

After being blocked from entering Platform Nine and Three-Quarters at King's Cross railway station, Harry and Ron fly the car to Hogwarts, where they crash into the Whomping Willow. Ron's wand is broken, and they each receive detention, during which Harry hears a strange voice and subsequently finds caretaker Argus Filch's cat, Mrs Norris, petrified with a message written in blood: "The Chamber of Secrets has been opened, enemies of the heir... beware." One of Hogwarts' founders, Salazar Slytherin, supposedly constructed a secret Chamber containing a monster that only his heir can control, capable of purging the school of Muggle-borns. Suspecting Malfoy to be the heir, Harry, Ron, and Hermione plan to question him.

Harry's arm is broken by a rogue Bludger in a Quidditch match; while recovering, Dobby visits him and reveals he closed the barrier and made the rogue Bludger to force him to leave the school, in addition to the Chamber having been opened in the past. After students are found petrified, Harry is suspected of being the heir of Slytherin after communicating with a snake - an ability shared with Slytherin. Disguised as Crabbe and Goyle, using polyjuice potion, which they brew in a bathroom haunted by the ghost of Moaning Myrtle, Harry and Ron learn Malfoy is not the heir, but that a Muggle-born girl died when the Chamber was last opened 50 years ago. Harry finds an enchanted diary owned by a former student Tom Marvolo Riddle, who blames a young Rubeus Hagrid for opening the Chamber, leading to his expulsion.

When Hermione is petrified, Harry and Ron question Hagrid, who is sent to Azkaban by Minister of Magic Cornelius Fudge, while Lucius forces the school governors to remove Dumbledore from office. Hagrid discreetly tells the boys to "follow the spiders"; they venture into the Forbidden Forest and meet Hagrid's spider, Aragog, who reveals Hagrid's innocence and provides another clue to the Chamber's monster. A book page in Hermione's hand identifies the monster as a basilisk, a giant serpent that kills people who make direct eye contact; the petrified victims only saw it indirectly.

Ginny is taken into the Chamber, and the teachers nominate Lockhart to save her; Harry and Ron find Lockhart preparing to flee and expose him as a fraud. Deducing that Myrtle was the Muggle-born girl that the basilisk killed, they find the Chamber's entrance in the bathroom she haunts. Once inside, Lockhart tries to erase Harry and Ron's memories and take the credit, but his spell backfires when he uses Ron's broken wand, erasing his memory and causing a cave-in, separating Harry from Ron and Lockhart.

Harry enters the Chamber alone and finds Ginny unconscious and Riddle - Slytherin's heir and Voldemort's younger self - who reveals he used the diary to manipulate Ginny into reopening the Chamber. Harry expresses his loyalty to Dumbledore, whose pet phoenix Fawkes arrives with the Sorting Hat. Riddle summons the basilisk, who Fawkes blinds, and the Sorting Hat produces the Sword of Gryffindor, which Harry uses to kill the basilisk after a battle, but is poisoned by one of its fangs. Despite being injured, Harry stabs the diary with the basilisk fang, destroying Riddle and reviving Ginny. Harry is healed by Fawkes' tears and returns to Hogwarts with his friends and a baffled Lockhart. Harry learns that Dobby's master is Lucius, whom he accuses of planting the diary in Ginny's cauldron, and tricks him into freeing Dobby. Dumbledore is reinstated as headmaster, the basilisk's victims are healed, Hermione reunites with her friends, and Hagrid is released from Azkaban.