Lights, camera, action!
Harry Potter isn't like most kids. A) He's a wizard. B) He can't wait to go back to school.
See? We told you.
Harry's sitting in his bedroom suffering through yet another awful summer with his Muggle relatives on Privet Drive when a house-elf named Dobby shows up and starts making trouble for him. The magical little guy says there's a plot afoot to make Harry's year at Hogwarts truly awful.
Hey, it couldn't be worse than the life at the Dursleys. Harry will take his chances.
The whole house-elf episode leads to Harry getting locked in his bedroom, which means he has to be rescued by Ron Weasley in a flying Ford Anglia. You can't say wizards don't have style. Later, Harry winds up going shopping for his school supplies with Ron's family and runs into Draco Malfoy and his father, Lucius. The rotten apple doesn't fall far from the tree with this clan.
Pretty soon everyone is boarding the Hogwarts Express…but for some reason Ron and Harry can't cross the barrier to Platform 9 ¾. Instead, they end up taking Mr. Weasley's flying car to get there. The boys get in minor trouble and Harry gets detention with the new Defense Against the Dark Arts teacher, Gilderoy Lockhart, an extremely famous and extremely vain wizard who loves to tell everyone about all the adventures he's had. This guy invented the humble brag…minus the humble part.
As he's walking back from detention, Harry hears voices and comes across an ominous message written in blood on the wall in a corridor—"The Chamber of Secrets has been opened. Enemies of the heir, beware." It's not only messy, it's spooky too. Mr. Filch's cat, Mrs. Norris, has also been petrified.
Professor McGonagall explains that the Chamber of Secrets was allegedly built by one of the founders of Hogwarts, Salazar Slytherin. It's supposed to contain a horrible monster that only a future student—the heir of Slytherin—could control. What a perfect addition to a school! Harry, Ron, and Hermione think that Draco might be the heir of Slytherin and decide to brew a Polyjuice Potion to find out.
Later, during a Quidditch match, Harry is attacked by an out of control bludger that breaks his arm. That night Dobby appears again and reveals that he was responsible for the bludger and closing Platform 9 ¾. He's just trying to keep Harry safe. Gee, thanks, Dobby. What a pal you are. That night, another student is petrified.
At dueling club, Harry accidentally reveals that he can talk to snakes. It's awkward because Salazar Slytherin could do it, too. Maybe Harry is the heir of Slytherin? Once the Polyjuice Potion is ready, Harry and Ron pose as Crabbe and Goyle and find out that Malfoy isn't the heir of Slytherin. They do figure out that the Chamber of Secrets was opened years ago and that a Muggle-born student died last time.
Gulp.
Later, in the bathroom, Harry finds a blank diary with the name Tom Marvolo Riddle written in it. When he writes in the diary, it writes back to him. The diary also shows him a memory from fifty years ago. It shows Tom Riddle turning in Hagrid for opening the Chamber of Secrets. Turns out a student was killed by a monster that Hagrid had been hiding in the castle.
Betcha didn't see that coming.
The diary is stolen from Harry's room and Hermione is petrified on her way back from the library. Now one too many kids have been petrified and Hagrid is taken to Azkaban due to his past crimes. Dumbledore is sent away, too. To be fair, he hasn't done a real great job protecting the students of Hogwarts from the monster lurking inside the castle, has he?
Harry and Ron head into the Forbidden Forest where they encounter a ginormous spider—Hagrid's monster. The spider tells them that Hagrid didn't open the chamber and the monster in the chamber isn't a spider. It's something way worse. The boys narrowly escape being eaten by a bunch of huge spiders and return to the castle to find out that Ginny Weasley has been kidnapped and taken into the Chamber of Secrets by the monster. This day just keeps getting worse.
Harry and Ron get Gilderoy Lockhart to go with them into the chamber to save Ginny even though he reveals that he's just a fraud who made up all his heroic adventures. Figures. Lockhart tries to attack Harry and Ron, but his spell backfires, which causes a rockslide that separates Ron and Lockhart from Harry. That means Harry has to go into the Chamber of Secrets all alone. Time to put on your brave face, Harry.
Inside the chamber, Harry runs into Tom Riddle who appears as a "memory" from inside the diary. He's kidnapped Ginny and is draining her of her strength so he can come back to life. He also reveals that he's actually Lord Voldemort. Oh, and then he sics a huge snake called a basilisk on Harry.
Harry gets some help from Dumbledore's pet phoenix, Fawkes, and the sword of Godric Gryffindor and manages to slay the basilisk. He also stabs the diary with a basilisk fang to get rid of the memory of Tom Riddle for good. Phew.
After everyone is safe, Harry finds out that Dobby is a house-elf for the Malfoy family. He can't bear to see the little guy working for such jerks so he tricks Lucius Malfoy into giving Dobby a sock, which means that Dobby is a free elf.
And the happy ending just keeps getting better: Hermione is un-petrified (along with all the other students). Hagrid is released from prison. Dumbledore cancels end of the year exams. Everyone is happy. Aside from the fact that a bunch of children almost died, it's been another awesome year at Hogwarts.