Harry Potter and the Methods of Rationality

and told the quill, "Write these letters exactly as I say them: Z-P-G-B-S-Y, space, F-V-Y-I-R-E-B-A-G-U-R-G-E-R- R."

There were two kinds of codes in cryptography, codes that stopped your little brother from reading your message and codes that stopped major governments from reading your message, and this was the first kind of code, but it was better than nothing. In theory, no one should read it anyway; but even if they did, they wouldn't remember anything interesting unless they did cryptography first.

Harry then put that parchment in a parchment envelope, and with his wand melted a little green wax to seal it.

In principle, of course, Harry could've done all that hours earlier, but somehow waiting until after he heard the message from Professor McGonagall's own lips seemed less like Messing With Time.

Harry then put that envelope inside another envelope, which already contained another sheet of paper with other instructions, and five silver Sickles.

He closed that envelope (which already had a name written on the outside), sealed it with more green wax, and pressed a final Sickle into that seal.

Then Harry put that envelope into the very last envelope on which was written in large letters the name "Merry Tavington".

And Harry peeked around the bend to where the scowling portrait that served as the door to the Slytherin dorms waited; and as he did not wish the portrait to recall not-seeing anyone invisible, Harry used the Hover Charm to float the envelope to the scowling man, and tap it against him.

The scowling man looked down at the envelope, peering at it through a monocle, and sighed, and turned around to face toward the inside of the Slytherin dorms, and called, "Message for Merry Tavington!"

The envelope was then allowed to fall to the floor.

A few moments later the portrait door opened, and Merry snatched up the envelope from the floor.

She would open it up and find a Sickle and an envelope addressed to a fourth-year student named Margaret Bulstrode.

(Slytherins did this sort of thing all the time, and a Sickle definitely constituted a rush order.)

Margaret would open her envelope, and find five Sickles along with an envelope to be dropped off in an unused classroom...

...after she used her Time-Turner to go back five hours...

...whereupon she would find another five Sickles waiting for her, if she got there quickly.

And an invisible Harry Potter would be waiting in that classroom from three PM to three-thirty, just in case someone tried the obvious test.

Well, it had been obvious to Professor Quirrell, anyway.

It had also been obvious to Professor Quirrell that (a) Margaret Bulstrode had a Time-Turner and (b) she wasn't very strict about how she used it, e.g. telling her younger sister really good pieces of gossip "before" anyone else had heard.

Some of the tension leaked off Harry as he strode away from the portrait door, still invisible. Somehow his mind had still managed to worry about the plan, even knowing that it had already succeeded. Now there remained only the confrontation with Dumbledore, and then he was done for the day... he'd go to the Headmaster's gargoyles at 9PM, since doing it at 8PM would seem more suspicious. This way he could claim that he'd just misunderstood what Professor McGonagall had meant by "afterward"...

The obscure pain clutched at Harry's heart again as he thought of Professor McGonagall.

So Harry retreated a little further into his dark side, which had worn the calm expression and kept the fatigue off his face, and kept walking.

There would come a reckoning, but sometimes you had to borrow everything you could today, and let the payments come due tomorrow.

Even Harry's dark side was feeling the exhaustion by the time the spiraling staircase had delivered him to the great oaken door that was the final gate to Dumbledore's office; but since Harry was now legally four hours past his natural bedtime, it was safe to let some of the fatigue show, the physical if not the emotional.

The oaken door swung open -

Harry's eyes had already been focused in the direction of the great desk, the throne behind it; so it took a moment to register that the throne was empty, the desk barren but for a single leatherbound volume; and then Harry shifted his gaze to see the wizard standing among his fiddly things, the mysterious unknown devices in their scores. Fawkes and the Sorting Hat occupied their respective perches, a bright cheerful blaze crackled in a nook that Harry had not before realized was a fireplace, and there were the two umbrellas and three red slippers for left feet. All things in their place and in their customary appearance except the old wizard himself, standing tall and dressed in robes of the most formal black. It came as a shock to the eyes, those robes on that person, it was as if Harry had seen his father wearing a business suit.

Very ancient was the appearance of Albus Dumbledore, and sorrowful.

"Hello, Harry," said the old wizard.

From within an alternate self maintained like an Occlumency construct, an innocent-Harry who had absolutely no idea what was happening inclined his head coldly, and said, "Headmaster. I expect you've heard back from Deputy Headmistress McGonagall by now, so if it's fine by you, I would really like to know what is going on."

"Yes," said the old wizard, "it is time, Harry Potter." The back straightened, only slightly for the wizard had already been standing straight; but somehow even that small change made the wizard seem a foot taller, and stronger if not younger, formidable though not dangerous, his potency gathered about him like a cowl. In a clear voice, then, he spoke: "This day your war against Voldemort has begun."

"What?" said the outer Harry who knew nothing, while something watching from inside thought much the same