"So, Mr. Potter. Any progress on finding the Chamber of Secrets?"
No, thought Harry. But to maintain plausible deniability, you needed a general policy of sometimes evading questions even when you had nothing to hide... "With respect, Professor Quirrell, if I had made such progress, it is not quite obvious to me that I should tell you about it."
Professor Quirrell sipped from his own waterglass again. "Well then, Mr. Potter, I shall freely tell you what I know or suspect. First, I believe the Chamber of Secrets is real, as is Slytherin's Monster. Miss Myrtle's death was not discovered until hours after her demise, even though the wards should have alerted the Headmaster instantly. Therefore her murder was performed either by Headmaster Dippet, which is unlikely, or by some entity which Salazar Slytherin keyed into his wards at a higher level than the Headmaster himself. Second, I suspect that contrary to popular legend, the purpose of Slytherin's Monster was not to rid Hogwarts of Muggleborns. Unless Slytherin's Monster were powerful enough to defeat the Headmaster of Hogwarts and all the teachers, it could not triumph by force. Multiple murders in secrecy would result in the school's closure, as nearly happened in 1943, or in the placing of new wards. So why Slytherin's Monster, Mr. Potter? What true purpose does it serve?"
"Ah..." Harry dropped his gaze to his waterglass and tried to think. "To kill anyone who got into the Chamber and didn't belong there -"
"A monster powerful enough to defeat a team of wizards that had broken past the best wards Salazar could place on his Chamber? Unlikely."
Harry was feeling a bit pressured now. "Well, it's called the Chamber of Secrets, so maybe the Monster has a secret, or is a secret?" For that matter, just what sort of secrets were in the Chamber of Secrets in the first place? Harry hadn't done a lot of research on the subject, in part because he'd gotten the impression that nobody knew anything -
Professor Quirrell was smiling. "Why not just write the secret down?"
"Ahhh..." said Harry. "Because if the Monster spoke Parseltongue, that would ensure that only a true descendant of Slytherin could hear the secret?"
"Easy enough to key the wards on the Chamber to a phrase spoken in Parseltongue. Why go to the trouble of creating Slytherin's Monster? It cannot have been easy to create a creature with a lifespan of centuries. Come, Mr. Potter, it should be obvious; what are the secrets that can be told from one living mind to another, but never written down?"
Harry saw it then, with a burst of adrenaline that started his heart racing, his breath coming faster. "Oh."
Salazar Slytherin had been very cunning indeed. Cunning enough to come up with a way to bypass the Interdict of Merlin.
Powerful wizardries couldn't be transmitted through books or ghosts, but if you could create a long-lived enough sentient creature with a good enough memory -
"It seems very probable to me," said Professor Quirrell, "that He-Who-Must-Not-Be-Named began his climb to power with secrets obtained from Slytherin's Monster. That Salazar's lost knowledge is the source of You-Know-Who's extraordinarily powerful wizardry. Hence my interest in the Chamber of Secrets and the case of Mr. Hagrid."
"I see," Harry said. And if he, Harry, could find Salazar's Chamber of Secrets... then all of the lost knowledge that Lord Voldemort had obtained would be his as well.
Yes. That was just how the story should go.
Add in Harry's superior intelligence and some original magical research and some Muggle rocket launchers, and the resulting fight would be completely one-sided, which was exactly how Harry wanted it.
Harry was grinning now, a very evil grin. New priority: Find everything in Hogwarts that looks remotely like a snake and try speaking to it. Starting with everything you've already tried, only this time be sure to use Parseltongue instead of English - get Draco to let you into the Slytherin dorms -
"Don't become too excited, Mr. Potter," said Professor Quirrell. His own face had become expressionless, now. "You must continue thinking. What were the Dark Lord's parting words to Slytherin's Monster?"
"What?" Harry said. "How could either of us possibly know that?"
"Visualize the scene, Mr. Potter. Let your imagination fill in the details. Slytherin's Monster - probably some great serpent, so that only a Parselmouth may speak to it - has finished imparting all of the knowledge it possesses to He-Who-Must-Not-Be-Named. It conveys to him Salazar's final benediction, and warns him that the Chamber of Secrets must now remain closed until the next descendant of Salazar should prove cunning enough to open it. And he who will become the Dark Lord nods, and says to it -"
"Avada Kedavra," said Harry, suddenly feeling sick to his stomach.
"Rule Twelve," Professor Quirrell said quietly. "Never leave the source of your power lying around where someone else can find it."
Harry's gaze dropped to the tablecloth, which had decorated itself in a mournful pattern of black flowers and shadows. Somehow that seemed... too sad to be imagined, Slytherin's great snake had only wanted to help Lord Voldemort, and Lord Voldemort had just... there was something unbearably sorrowful about it, what sort of person would do that to a being who'd offered them nothing but friendship... "Do you think the Dark Lord would have -"
"Yes," Professor Quirrell said flatly. "He-Who-Must-Not-Be-Named left quite a trail of bodies behind him, Mr. Potter; I doubt he would have omitted that one. If there were any artifacts left there that could be moved, the Dark Lord would have taken those with him as well. There might still be something worth seeing in the Chamber of Secrets, and to find it would prove yourself the true Heir of Slytherin. But do not raise your hopes too high. I suspect that all you will find is the remains of Slytherin's Monster resting quietly in its grave."
They sat in silence for a while.
"I could be wrong," said Professor Quirrell. "In the end it is only a guess. But I did wish to warn you, Mr. Potter, so that you would not be too sorely disappointed."
Harry nodded shortly.
"One might even regret your infant self's victory," said Professor Quirrell. His smile twisted. "If only You-Know-Who had lived, you might have persuaded him to teach you some of the knowledge that would have been your heritage, from one Heir of Slytherin to another." The smile twisted further, as though to mock the obvious impossibility, even given the premise.
Note to self, thought Harry, with a slight chill and an edge of anger, make sure to extract my heritage out of the Dark Lord's mind, one way or another.
There was another silence. Professor Quirrell was looking at Harry as though waiting for him to ask something.
"Well," said Harry, "so long as we're on the topic, can I ask how you think the whole Parselmouth business actually -"
There came a knock at the door, then. Professor Quirrell raised a cautionary finger, then opened the door with a wave. The waitress entered, balancing a huge platter with their meals as though the whole assembly weighed nothing (which was in fact probably the case). She gave Professor Quirrell his bowl of green soup, and a glass of his usual Chianti; and set down before Harry a plate of small meat strips smothered in a heavy-looking sauce, plus a glass of his accustomed treacle soda. Then she bowed, managing to make it seem like sincere respect rather than perfunctory acknowledgment, and departed.
When she was gone, Professor Quirrell held up a finger for silence again, and drew his wand.
And then Professor Quirrell began performing a certain series of incantations that Harry recognized, making him take a sharp breath. It was the series and ordering that Mr. Bester had used, the full set of twenty-seven spells that you would perform before discussing anything of truly great import.