Harry Potter and the Methods of Rationality

On the plus side, the Comed-Tea, which had once seemed all-powerful and all-unbelievable, had turned out to have a much simpler explanation. Which he'd missed merely because the truth was completely outside his hypothesis space or anything that his brain had evolved to comprehend. But now he actually had figured it, probably. Which was sort of encouraging. Sort of.

Harry glanced down at his watch. It was nearly 11AM, he'd gotten to sleep last night at 1AM, so in the natural state of affairs he'd go to sleep tonight at 3AM. So to go to sleep at 10PM and wake up at 7AM, he should go back five hours total. Which meant that if he wanted to get back to his dorm at around 6AM, before anyone was awake, he'd better hurry up and...

Even in retrospect Harry didn't understand how he'd pulled off half the stuff involved in the Prank. Where had the pie come from?

Harry was starting to seriously fear time travel.

On the other hand, he had to admit that it had been an irreplaceable opportunity. A prank you could only pull on yourself once in a lifetime, within six hours of when you first found out about Time- Turners.

In fact that was even more puzzling, when Harry thought about it. Time had presented him with the finished Prank as a fait accompli, and yet it was, quite clearly, his own handiwork. Concept and execution and writing style. Every last part, even the ones he still didn't understand.

Well, time was a-wasting and there were at most thirty hours in a day. Harry did know some of what he had to do, and he might figure out the rest, like the pie, while he was working. There was no point putting it off. He couldn't exactly accomplish anything stuck here in the future.

Five hours earlier, Harry was sneaking into his dorm with his robes pulled up over his head as a thin sort of disguise, just in case someone was already up and about and saw him at the same time as Harry lying in his bed. He didn't want to have to explain to anyone about his little medical problem with Spontaneous Duplication.

Fortunately it seemed that everyone was still asleep.

And there also seemed to be a box, wrapped in red and green paper with a bright golden ribbon, lying next to his bed. The perfect, stereotypical image of a Christmas present, although it wasn't Christmas.

Harry crept in as softly as he could manage, just in case someone had their Quieter turned down low.

There was an envelope attached to the box, closed by plain clear wax without a seal impressed.

Harry carefully pried the envelope open, and took out the letter inside.

The letter said:

This is the Cloak of Invisibility of Ignotus Peverell, passed down through his descendants the Potters. Unlike lesser cloaks and spells it has the power to keep you hidden, not merely invisible. Your father lent it to me to study shortly before he died, and I confess that I have received much good use of it over the years.

In the future I shall have to get along with Disillusionment, I fear. It is time the Cloak was returned to you, its heir. I had thought to make this a Christmas present, but it wished to come back to your hand before then. It seems to expect you to have need of it. Use it well.

No doubt you are already thinking of all manner of wonderful pranks, as your father committed in his day. If his full misdeeds were known, every woman in Gryffindor would gather to desecrate his grave. I shall not try to stop history from repeating, but be MOST careful not to reveal yourself. If Dumbledore saw a chance to possess one of the Deathly Hallows, he would never let it escape his grasp until the day he died.

A Very Merry Christmas to you.

The note was unsigned.

"Hold on," Harry said, pulling up short as the other boys were about to leave the Ravenclaw dorm. "Sorry, there's something else I've got to do with my trunk. I'll be along to breakfast in a couple of minutes."

Terry Boot scowled at Harry. "You'd better not be planning to go through any of our things."

Harry held up one hand. "I swear that I intend to do nothing of the sort to any of your things, that I only intend to access objects that I myself own, that I have no pranking or otherwise questionable intentions towards any of you, and that I do not anticipate those intentions changing before I get to breakfast in the Great Hall."

Terry frowned. "Wait, is that -"

"Don't worry," said Penelope Clearwater, who was there to guide them. "There were no loopholes. Well- worded, Potter, you should be a lawyer."

Harry Potter blinked at that. Ah, yes, Ravenclaw prefect. "Thank you," he said. "I think."

"When you try to find the Great Hall, you will get lost." Penelope stated this in the tones of a flat, unarguable fact. "As soon as you do, ask a portrait how to get to the first floor. Ask another portrait the instant you suspect you might be lost again. Especially if it seems like you're going up higher and higher. If you are higher than the whole castle ought to be, stop and wait for search parties. Otherwise we shall see you again four months later and you will be five months older and dressed in a loincloth and covered in snow and that's if you stay inside the castle."

"Understood," said Harry, swallowing hard. "Um, shouldn't you tell students all that sort of stuff right away?"

Penelope sighed. "What, all of it? That would take weeks. You'll pick it up as you go along." She turned to go, followed by the other students. "If I don't see you at breakfast in thirty minutes, Potter, I'll start the search."

Once everyone was gone, Harry attached the note to his bed - he'd already written it and all the other notes, working in his cavern level before everyone else woke up. Then he carefully reached inside the Quietus field and pulled the Cloak of Invisibility off Harry-1's still-sleeping form.