He sees Mrs. Norris hanging there and accuses Harry of killing her.
Professor Dumbledore pulls Filch, Harry, Ron, Hermione, and Professors Lockhart, Snape, and McGonagall into Lockhart's office nearby.
Professor Dumbledore announces that Mrs. Norris isn't dead; she's Petrified.
Filch insists it was Harry: "You saw what he wrote on the wall! He found – in my office – he knows I'm a – I'm a – [...] He knows I'm a Squib!" (9.27).
(A Squib is a person born to magical parents who can't do magic themselves.)
Professor Snape agrees that "Potter and his friends may have simply been in the wrong place at the wrong time" (9.31).
Then, why weren't they at the Halloween Feast?
Harry gives their airtight alibi: hundreds of ghosts saw them at Nearly Headless Nick's deathday party.
So, why didn't they come to the Halloween Feast afterwards?
Harry can't say that he heard a voice no one else could hear talking about killing.
He claims that they weren't hungry.
Professor Dumbledore reminds Snape, "Innocent until proven guilty" (9.42).
Professor Dumbledore promises Filch that they can heal Mrs. Norris just as soon as Professor Sprout's Mandrakes have gotten big enough to make a restorative potion.
Harry, Ron, and Hermione are allowed to go back to Gryffindor Tower.
Ron confirms that Harry was right not to say anything about the murderous voice: "Hearing voices no one else can hear isn't a good sign, even in the Wizarding world" (9.52).
Ron finally explains to Harry what a Squib is: "Kind of the opposite of Muggle-born wizards, but Squibs are quite unusual" (9.59).
Over the next few days, all anyone can talk about is the attack on Mrs. Norris.
Ginny Weasley seems particularly upset about it, since, Ron tells us, she is "a great cat lover" (9.63).
Hermione is spending all her time in the library looking for clues on what has happened.
Harry notices Justin Finch-Fletchley turning back and going the opposite direction the minute he sees Harry.
Harry is confused.
Hermione tells Ron and Harry that all the school library's copies of Hogwarts: A History have been checked out.
Everyone in the school is looking for information on the Chamber of Secrets.
Unfortunately, Hermione can't remember what the Chamber is.
During their History of Magic class with dead (and deadly boring) Professor Binns, Hermione interrupts his lecture to ask what the Chamber of Secrets is.
Professor Binns dismisses the Chamber of Secrets as a legend.
Hermione persists in asking him, though.
Professor Binns is so "thrown by such an unusual show of interest" (9.96) that he finally explains.
Hogwarts was apparently founded over a thousand years ago by two witches and two wizards: Helga Hufflepuff, Rowena Ravenclaw, Godric Gryffindor, and Salazar Slytherin.
They worked together in harmony for several years, "seeking out youngsters who showed signs of magic and bringing them to the castle to be educated" (9.100).
Then, Slytherin and the other founders fell into a serious argument.
The other founders felt that the school should be open to all children who showed magical talent.
Yet Slytherin wanted to limit Hogwarts enrollment to students from magical families.
He didn't want any Muggle-born students at Hogwarts.
So Slytherin left Hogwarts when the other founders refused to give in.
Then, legend goes, "Slytherin had built a hidden chamber in the castle, of which the other founders knew nothing" (9.102).
No one can open this hidden chamber except a direct heir of Slytherin.
Slytherin's heir would be able "to unseal the Chamber of Secrets, unleash the horror within, and use it to purge the school of all who were unworthy to study magic" (9.103).
Professor Binns dismisses this legend as nonsense and goes back to his usual lesson.
After class, Ron claims that Salazar Slytherin was a loony.
Harry starts to worry about himself: after all, the Sorting Hat initially wanted to put Harry in Slytherin rather than Gryffindor.
As they rush down the hall to their next class, Harry sees Colin Creevey.
Colin tries to tell Harry, "a boy in my class has been saying you're —" (9.125).
But the crowd pushes Colin on before he can finish.
Harry realizes that there are rumors going around that he is Slytherin's heir.
Harry, Ron, and Hermione go back to the scene of the crime to see if they can find anything.
They do notice something weird: a line of spiders trying to get out of the castle.
Ron admits that he hates spiders: "If you must know, when I was three, Fred turned my – my teddy bear into a great big filthy spider because I broke his toy broomstick...you wouldn't like them either if you'd been holding your bear and suddenly it had too many legs and" (9.148).
Harry recalls that there was a lot of water on the floor that night.
It must have come from the nearby girls' bathroom.
They go in to have a look.
The bathroom is home to a miserable, whining ghost girl named Moaning Myrtle.
She is extremely quick to take offense: "My life was nothing but misery at this place and now people come along ruining my death" (9.167).
She doesn't recall seeing anything the night that Mrs. Norris was Petrified.
She was too busy being a giant drama queen.
As Harry, Ron, and Hermione come out of the girls' bathroom, Percy Weasley spots them.
He's furious that they are breaking school rules and worrying Ginny.
So he takes five points from Gryffindor and gives them detention. Percy's a prefect, which means he can discipline other students for misbehavior.
In the Common Room that night, Harry, Ron, and Hermione discuss what to do next.
Ron is sure that the Heir of Slytherin must be Draco Malfoy.
Draco obviously agrees that Muggle-borns have no place at Hogwarts and his whole family is in Slytherin. He must be the Heir!
To prove it, Hermione suggests that they make Polyjuice Potion.
Polyjuice Potion allows you to transform into someone else for an hour.
If she, Harry, and Ron turned into friends of Draco's, they might be able to get him to confess.