Harry Potter and the Methods of Rationality

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.

If the discussion of the Chamber of Secrets hadn't counted as important -

When Professor Quirrell was done - he'd performed thirty spells, three of which Harry hadn't heard before - the Defense Professor said, "Now we shall not be interrupted for a time. Can you keep a secret, Mr. Potter?"

Harry nodded.

"A serious secret, Mr. Potter," Professor Quirrell said. His eyes were intent, his face grave. "One which could potentially send me to Azkaban. Think about it before you reply."

For a moment Harry didn't even see why the question should be hard, given his growing collection of secrets. Then -

If this secret could send Professor Quirrell to Azkaban, that means he's done something illegal...

Harry's brain performed a few calculations. Whatever the secret, Professor Quirrell did not think his illegal act would reflect badly on him in Harry's eyes. There was no advantage to be gained from not hearing it. And if it did reveal something wrong with Professor Quirrell, then it was very much to Harry's advantage to know it, even if he had promised not to tell anyone.

"I never had very much respect for authority," Harry said. "Legal and governmental authority included. I will keep your secret."

Harry didn't bother asking whether the revelation was worth the danger it would pose to Professor Quirrell. The Defense Professor wasn't stupid.

"Then I must test whether you are truly a descendant of Salazar," said Professor Quirrell, and stood up from his chair. Harry, prompted more by reflex and instinct than calculation, shoved himself up out of his own chair as well.

There was a blur, a shift, a sudden motion.