This is a piece of meta-fanfiction based on the excellent fic Harry Potter and the Methods of Rationality, which in turn is based on Harry Potter. It contains extreme spoilers for the former, up to almost the end; if you care about that, you should stop reading now.

JK Rowling owns Harry Potter, and Eliezer Yudkowsky wrote HPMOR.

This fic is written based on HPMOR up to Chapter 105 or so, but deviates sharply after that - the Dark Lord gets the Philosophers' Stone and then leaves Hogwarts peacefully according to a prior agreement, leaving Harry behind with more time to plan and think. Some other changes have been made as well.

This is my first story actually posted on FFNet, so it's almost certain I've made several mistakes. Feedback of all kinds, positive and negative, is appreciated.

Harry focused his mind, raised his wand again and spoke. "Expecto Patronum!"

It didn't work. He hadn't really expected it to work, since if an Occlumency barrier could cast a Patronus Charm Professor Quirrell would certainly have been capable of it - but until he heard back from Draco it was at least worth a try.

Professor Quirrell had taken the Philosopher's Stone, and left Hogwarts without another word. And nothing had happened since then. No news, no mysterious deaths, no sudden collapses of all the world's governments.

And this would have been very reassuring had Professor Quirrell not promised to refrain from harming Harry or any staff or students of Hogwarts for a period of one week after he attained the Stone.

Harry couldn't shake the feeling that this simply meant a great many people would die extremely quickly in (he checked his watch) one-hundred and fifty-eight hours and twenty-five minutes from now. Yesterday he would have been confident in his ability to prepare for anything, given a full week in Hogwarts.

Today he was no longer that confident. Professor Quirrell was a version of himself with far more magical power, far more life experience, multiple powerful artefacts, and who had spent years on preparation and research. Harry knew he was looking for a way to defeat Professor Quirrell, but he simply couldn't imagine what that way would be. Over a hundred Horcruxes, all of them competently hidden, and with the ability to bring Professor Quirrel back almost instantly, into any suitable victim.

(Harry fought down another wave of despair as he recalled how Quirrell had gained this last ability. His own feelings about responsibility notwithstanding, remorse was not useful.)

Harry had sent Patronus Charms to both Dumbledore and Perenell. Whether they were good people or not, they seemed genuinely preferable to the alternative. He hadn't heard back from either of them.

In the case of Perenell, that probably meant she was either dead or captured. Harry had cast his Patronus only a few minutes after Quirrell departed, but it was looking increasingly likely that Professor Quirrell had expected that and gotten there first.

Harry wasn't sure about Dumbledore. The Headmaster should have been covered by Quirrell's agreement not to harm the staff or students of Hogwarts for a week, but he hadn't responded to Harry's Patronus, and the Patronus wouldn't report on its surroundings or on whether it had reached him. (This didn't augur well for Harry's plan to locate Quirrell's Horcruxes by sending Patronus Charms to them and getting the Patronuses to report where they were, but he doubted that would have been enough in any case). Maybe Dumbledore had tried to protect Perenell/Nicholas Flamel from someone he still imagined as merely the Dark Lord, and died for it? Quirrell's promise wouldn't have held him back from killing anyone who directly opposed him...

Nihil supernum, the Sword of Gryffindor had read, and Harry had learned enough Latin by now to have a better idea of what it meant. But that philosophy seemed to fall flat when you simply didn't know what to do. Heroism or not, Harry would take help from anyone who might be able to offer it at this point.

Which was why he was currently standing in a Hogwarts corridor, waiting to hear back from Draco.

"And he who will become the Dark Lord nods, and says to it ... Avada Kedavra."

Professor Quirrell had certainly claimed that Slytherin's monster was dead. But an idea had come to Harry, planted in his mind when he learned the truth of Parseltongue.

"Sslytherin not sstupid." The praise might seem faint, but it was as high as Quirrell would ever give. If Harry had heard of the Chamber of Quirrell, set into Hogwarts by Quirinus Quirrell to yield up his secrets to heirs in later generations, and he had then heard that one Heir of Quirrell had slain Quirrell's monster and rendered the Chamber useless for those that came after him...then his suspension of disbelief would simply have shattered.

Because Professor Quirrell would have thought of that. And, if he were setting a Chamber he intended for more than one Heir to be able to access, he would have taken measures to ensure it would survive.

And if there was anyone, any wizard past or present, who you might expect to be Quirrell's equal in plotting...then Salazar, founder of House Slytherin, who helped raise Hogwarts from the ground, who wrought his Chamber to bypass the Interdict of Merlin and who placed the Parseltongue Curse on his bloodline to ensure that his children would always be able to trust one another, had to be on the shortlist.

Several parts of Harry had raised objections to this. His inner Slytherin had pointed out that Salazar Slytherin had in fact died - well, not for certain, but that definitely seemed like the way to bet - while Professor Quirrell had not. Even if you credited Lord Voldemort's Muggle upbringing as giving him an improved perpective, that couldn't be a good sign. Gryffindor had suggested that hoping for Salazar Slytherin to have done something clever was just an attempt to pass off responsiblity for dealing with Quirrell to someone else.

No part of Harry had given him any better-sounding ideas, though, so here he was.

"Ssalutationss from Sslytherin to Sslytherin - if you would sseek my ssecretss, sspeak to my ssnake."

Harry had been working on the assumption that the message was simply to tell potential Heirs that the Chamber was there and that it really existed, and that the riddle of finding the Chamber would be separate from the message. He had spent several fruitless weeks earlier in the year scouring Hogwarts for things that looked like snakes and speaking to them in Parseltongue, and it had only recently occurred to him that he had been doing it wrong.

Because 'search the entirety of Hogwarts for a snake to talk to' wasn't the sort of challenge Salazar Slytherin would have expected to identify his Heir. Draco had told him a proverb once, that 'Ravenclaw was sister to Slytherin', and Harry had seen the point of it at once. If he'd been searching for the Chamber of Hufflepuff, demonstrating his Conscientiousness and Industry by searching every square inch of Hogwarts would be a reasonable approach. But Salazar Slytherin or Rowena Ravenclaw would have set a different kind of challenge.

And it had only recently occurred to Harry to look at the Hat's message as if it were itself the riddle to find the Chamber of Secrets, look at it as if the Ravenclaw door had posed it as its question.

"...sspeak to my ssnake."

What snakes were there that Salazar Slytherin could refer to as 'his'? Oh, the obvious answer was his Monster, but that wouldn't help you actually find the Chamber, so if you assumed that line was the riddle it had to mean a different snake. Salazar Slytherin had helped raise Hogwarts, and so you could argue that any snake-like thing in Hogwarts belonged to him, but that didn't seem convincing to Harry. But if Slytherin had owned a pet snake, or some kind of snakelike familiar, or something similar that unambiguously belonged to him and only him...

And then Harry had remembered a book he'd read once.

Which was why he was currently standing in a Hogwarts corridor, waiting to hear back from Draco.

The silver serpent slithered out of a wall behind Harry, with his own glowing Patronus behind it, and it spoke in Draco Malfoy's voice.

"Harry! I've been trying to reach you for hours, but I couldn't get through! I figured out what-"

Harry ignored the voice as it continued on. He didn't know how exactly the Defense Professor had tricked Draco - Confundus, Legilimency, False Memory Charms, or something else - but it didn't seem crucial at this point. Instead, he focused on the Patronus itself, saw it as a snake, and spoke in Parseltongue.

"I sseek the ssecretss of Ssalazar Sslytherin. Where sshould I ssearch?"

Draco's voice coming from the Patronus cut out abruptly, and its moonlight-silvery form stared up at him with eyes that suddenly seemed far more alive than he had ever seen in a Patronus.

"Hello, my Heir."