Harry is once again back 'home' with the Dursleys, and his summer holidays are not going to plan. The Dursleys have forbidden his broom, wand and all of his schoolbooks. Harry has not yet received any letters from his friends, Ron and Hermione. On his 12th birthday, Dobby the house elf, arrives to warn Harry that he will be in mortal danger if he returns to Hogwarts. Harry is determined to return, as it's the only true home he has ever known, so Dobby destroys the cake for an important dinner party attended by Uncle Vernon's potential client and the client's wife. The Ministry Of Magic send a letter explaining Harry cannot use magic outside of school as he will be expelled. No longer afraid of this, Uncle Vernon tells Harry he cannot return to Hogwarts and puts bars on Harry's window.

Ron, along with his twin brothers, Fred and George rescue Harry and take him to their home in their flying car. Ginny, Ron's younger sister is just starting Hogwarts in her first year and is overwhelmed when she meets Harry. After a pleasent month living with them everyone heads to Platform 9¾ to take the Hogwarts Express back to school. To their shock, Harry and Ron are unable to enter the barrier between platforms 9 and 10. In desperation, they steal the flying car and fly to Hogwarts. They crash into the Whomping Willow, which immediately attacks, damaging the car and snapping Ron's wand in half. The wrecked car then disappears into the Forbidden Forest.

Events at school take a turn for the worse when the legendary Chamber Of Secrets is opened and a monster begins to stalk the castle, petrifying anyone who meets its gaze. According to legend, the Chamber was built by one of the Hogwarts Founders, Salazar Slytherin, and can be opened only by his heir, in order to purge Hogwarts of 'all those who were unworthy to study magic' or 'Muggle-borns'. Many suspect Harry is the heir of Slytherin because, while trying to save another student during a duel against Malfoy, he inadvertently speaks Parseltongue, the ability to talk to snakes. This being a rare talent.
The Dursleys were so mean that hideous that summer that all Harry Potter wanted was to get back to the Hogwarts School for Witchcraft and Wizardry. But just as he's packing his bags, Harry receives a warning from a strange, impish creature named Dobby who says that if Harry Potter returns to Hogwarts, disaster will strike.

And strike it does. For in Harry's second year at Hogwarts, fresh torments and horrors arise, including an outrageously stuck-up new professor, Gilderoy Lockheart, a spirit named Moaning Myrtle who haunts the girls' bathroom, and the unwanted attentions of Ron Weasley's younger sister, Ginny.

But each of these seem minor annoyances when the real trouble begins, and someone--or something--starts turning Hogwarts students to stone. Could it be Draco Malfoy, a more poisonous rival than ever? Could it possibly be Hagrid, whose mysterious past is finally told? Or could it be the one everyone at Hogwarts most suspects...Harry Potter himself?

哈利在暑假时受到一只家养小精灵多比的警告，让他不要去学校，哈利不同意，小精灵就把哈利姨妈家的一个PARTY给搞杂了，魔法部认为时哈利施展了魔法，给他寄来一张警告，他姨夫也就知道他不能在假期使用魔法了，于是把他锁了起来。
弗雷德乔治和罗恩开着辆会飞的汽车把哈利救了出来，带到了罗恩的家里
他们去学校的时候车站的九又四分之三站台突然关闭，哈利和罗恩没能赶上火车，两人开着罗恩爸爸的那辆会飞的车赶到学校，却被斯内普抓住，罗恩的魔杖也坏了
一个长的很帅很能吹牛出过很多本书的巫师当上他们的黑魔法防御术教师，马尔福进了斯莱特林的魁地奇队，也是找球手，哈利今年一直听到一个只有他才能听到的可怕声音
万圣节那天哈利罗恩赫敏追着这个声音发现了费尔奇的猫被石化了，墙上写着关于密室和斯莱特林继承人的一些话
后来又有很多这样的事故，哈利被认为就是那继承人，因为他偶然发现他能跟蛇对话，而那是斯莱特林独特的本事
后来赫敏被袭击了，哈利发誓要找出凶手，他找到一本属于一个叫汤姆·里德尔的人的日记，他发现他可以用那本日记和里德尔对话，里德尔告诉他打开密室的人是海格
哈利不信去找海格，根据海格留下的线索他找到了海格当初在城堡里养的那只被认为是密室里的怪物，是只蜘蛛但不属于密室，它告诉哈利密室里的那只怪物是它们蜘蛛们最怕的生物
哈利和罗恩在被石化的赫敏手里发现一张图书馆的书里撕下来的一页纸，明白了密室里的怪物是一只蛇怪
这时传来罗恩的妹妹金妮被绑架到密室的消息，哈利和罗恩进入了密室，向里面的怪物发出了挑战……
打开密室的是里德尔的日记里的他的记忆……汤姆·里德尔就是年轻时的伏地魔，他通过日记控制了金妮，利用金妮造成了那些袭击事件
哈利和蛇怪展开了搏斗，在邓布利多的凤凰福克斯的格兰芬多宝剑的帮助下哈利杀掉了蛇怪，毁掉了日记，救出了金妮……