Opinion - Continuation of Harry Potter and The Sorcerer's Stone, all characters have plot relevance and are very deep and flushed out. Story has a satisfying conclusion.
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A house elf, named Dobby, ruins a dinner party that Harry's Uncle Vernon was running, and Harry was jailed in his room as they thought he used magic to drop the cake on the guests. Harry is then freed by his friend Ron Weasley and his brothers on a flying car.
Hagrid was the one to open the Chamber of Secrets previously.
While at school, students have been turned into stone as a result of the "Chambers of Secrets" being opened. The rumors saying that it is a monster that is turning the students into stone. The students believe that the "Heir of Slytherin" was the one to open it.
Harry! Thank goodness!
During a dueling club, Harry's rival, Draco Malfoy, had summoned a snake at him, which tried to attack another student. Harry unknowingly talks to the snake and tells it to stop in Parseltongue, making people believe that he is the "Heir of Slytherin" and that he had opened the Chamber of Secrets.
I believe Lord Voldemort put a piece of his soul into the diary.
In a bathroon, Harry finds a magical diary, which tells him that the "Chamber of Secrets" had been opened before, and that Harry's friend Hagrid, a teacher, was the one to open it. When Hagrid was a student, he was blamed for opening the "Chamber of Secrets", and was expelled. Hagrid is then sent to prison for the time being as the authorities suspect him of opening the "Chamber of Secrets".
Using previous clues, Harry finds the Chamber of Secrets in order to rescue Ron's sister, Ginny. There he finds Tom Riddle, who was residing in the diary, and reveals himself to be the heir and summons the Basilisk. Harry kills the Basilisk and destroys the diary, which kills Riddle, and rescuing Ginny.
Harry then brings Ginny to Professor Dumbledore, the headmaster. Harry tells Professor Dumbledore about everything he knows about the Chamber of Secrets and how he defeated The Basilisk. They also discuss over Riddle's Diary, who he revealed was actually Lord Voldemort while he was still in schoo.
Professor, Lord Voldmort, I mean Tom Riddle, had a diary which opened the Chamber!