It's the second year at Hogwarts for Harry, Ron, and Hermione, and things aren't getting calm at all following last year. They're just getting more exciting. Harry Potter has definitely changed. He's wiser, less reactive to everything, and sees Hogwarts as his only home. Ron is the same clumsy wizard who likes to panic. Hermione has evolved the most. She's not nearly as bossy or rude, although she's still the most willing to study and learn of the trio.
The plot is as follows: Harry receives warnings not to return to Hogwarts. After Ron and his brothers rescue Harry from his still rather rude and mean uncle, aunt, and cousin, Harry returns to Hogwarts anyway. Strange mishaps occur to Harry as further warnings to leave, and at the same time there are random attacks against others, leaving students literally petrified.
Our trio of young wizards then learn about the chamber of secrets and what it holds, and that the heir of Slytherin will use it to extinguish muggle-born students. Worried that the heir has returned and is causing the random attacks, our trio plucks around for answers. Harry is accused of being the heir when it's discovered he can speak Parseltongue(Snake language). When Hermione winds up petrified, Harry and Ron seek and the chamber of secrets, leading to the truth. I'll save that for surprise.
Kenneth Branagh is well-cast as the pompous celebrity wizard Guilderoy Lockhart, hired as the kids' second "Defense Against the Dark Arts" professor. The particular standout here is new cast member Jason Isaacs, who is the very image of petty evil as Lucius, the father of Potter's nemesis Draco Malfoy. "Harry Potter" isn't just an action-fantasy story. This story introduces the important concept of "mug-bloods" (wizards with one or more non-wizard parent) and the theme of prejudice and bigotry shown by "pure-blood" wizards towards them.
The movie left me looking forward to the third installment, "Harry Potter and the Prisoner of Azkaban."