It's been a year since Harry Potter (DANIEL RADCLIFFE) attended Hogwarts, a school for wizards and witches run by Professors Dumbledore (RICHARD HARRIS) and McGonagall (MAGGIE SMITH). Once again living with his aunt and uncle, Vernon (RICHARD GRIFFITHS) and Petunia Dursley (FIONA SHAW), and their spoiled son, Dudley (HARRY MELLING), Harry wonders why he hasn't heard from his close friends and fellow students, Ron Weasley (RUPERT GRINT) and Hermione Granger (EMMA WATSON).
He soon learns that a house elf, Dobby (voice of TOBY JONES), has hidden their letters and is now trying to convince Harry not to return to the school for fear of something bad happening to him. Harry isn't sure what to make of that, but does make his way back to the school where he runs into the friendly groundskeeper, Rubeus Hagrid (ROBBIE COLTRANE) as well as rival student Draco Malfoy (TOM FELTON) and his equally mean and condescending father, Lucius Malfoy (JASON ISAACS).
He also meets Gilderoy Lockhart (KENNETH BRANAGH), the egocentric Professor of the Defense Against the Dark Arts who naturally clashes with the more stern and somber Professor Snape (ALAN RICKMAN) who's in control of the rival house to Harry's.
Things become more mysterious when Harry starts hearing odd voices and various people end up "petrified" in frozen stances. While others believe Harry to be responsible for that, Dumbledore and the others realize something far more menacing and familiar is at hand.
While they try to protect the students and decide whether or not to close the school, Harry, Ron and Hermione set out to figure out what's going on. In doing so, they encounter the spirits of former students Moaning Myrtle (SHIRLEY HENDERSON) and Tom Riddle (CHRISTIAN COULSON) and hear of the legend of the Chamber of Secrets. As they get closer to the truth, they find themselves in grave danger as they try to solve the mystery of what's occurring.