“Please, sir, don’t legends always have a basis in fact?”

Professor Binns was looking at her in such amazement, Harry was sure no student had ever interrupted him before, dead or alive.

“Well,” said Professor Binns slowly, “yes, one could argue that, I suppose.” He peered at Hermione as though he had never seen a student properly before. “However, the legend of which you speak is such a very sensational, even ludicrous tale ---”

But the whole class was now hanging on his every word. He looked dimly at them all, every face turned to his. Harry could tell he was thrown by such an unusual show of interest.

“Oh, very well,” he said, slowly, “Let me see.... the Chamber of Secrets... “You all know, of course, that Hogwarts was founded over a thousand years ago - the precise date is uncertain - by the four greatest witches and wizards of the age. The four houses are named after them: Godric Gryffindor, Helga Hufflepuff; Rowena Ravenclaw, and Salazar Slytherin, They built this castle together, far from prying Muggle eyes, for it was an age when magic was feared by common people, and witched and wizards faced much persecution.”

He paused, gazed blearily around the room, and continued.

“For a few years, the founders worked in harmony together, seeking out youngsters who showed signs of magic and bringing them to castle to be educated. But then disagreements sprang up between them. A rift began to grow between Slytherin and the others. Slytherin wished to be more selective about the students admitted to Hogwarts. He believed that magic learning should be kept within all-magic families. He disliked taking students of Muggle parentage, believing them to be untrustworthy. After a while, there was a serious argument on the subject between Slytherin and Gryffindor, and Slytherin left the school.”

Professor Binns paused again, pursing his lips, looking like a wrinkled old tortoise.

“Reliable historical sources tell us this much,” he said. “But these honest facts have been obscured by the fanciful legend of the Chamber of Secrets. The story goes that Slytherin had built a hidden chamber in the castle, of which the other founders knew nothing.

“Slytherin, according to the legend, sealed the Chamber of Secrets so that none would be able to open it until his own true heir arrived at the school. The heir alone 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.” There was a silence as he finished telling the story, but it wasn’t the usual sleepy science that filled Professor Binn’s classes. There was unease in the air as everyone continued to watch him, hoping for more. Professor Binns looked faintly annoyed.

“The whole thing is arrant nonsense, of course,” he said. “Naturally, the school has been searched for evidence of such a chamber, many times, by the most learned witches and wizards. A tale told to frighten the gullible.”

Hermione’s hand was back in the air.

“Sir, what exactly do you mean by ‘the horror within’ the Chamber?”

“That is believed to be some kind of monster that the Heir of Slytherin alone can control,” said Professor Binns in his dry, reedy voice.

The class exchanged nervous looks.

“I tell you, the thing does not exist,” said Professor Binns, shuffling his notes. “There is no Chamber and no monster.”

“But, sir,” said Seamus Finnigan, “if the Chamber can only be opened by Slytherin’s true heir, no one else would be able to find it, would they?”

“Nonsense, O’Flaherty,” said Professor Binns in an aggravated tone. “If a long succession of Hogwarts headmasters and headmistresses haven’t found the thing -”

“But, Professor,” piped up Parvati Patil, “you’d probably have to use Dark Magic to open it -”

“Just because a wizard doesn’t use Dark Magic doesn’t mean he can’t, Miss Pennyfeather,” snapped Professor Binns. “I repeat, if the likes of Dumbledore-”

“But maybe you’ve got to be related to Slytherin, so Dumbledore couldn’t -” began Dean Thomas, but Professor Binns had had enough.

“That will do,” he said sharply. “It is a myth! It does not exist! There is not a shred of evidence that Slytherin built so much as a secret broom cupboard! I regret telling you such a foolish story! We will return, if you please, to history, to solid, believable, verifiable fact!”

And within five minutes, the class had sunk back into its usual torpor. (149-52)