Harry Potter and the Methods of Rationality

Harry explained. Parseltongue didn't have words for the Muggle technology, but Harry described the function and Professor Quirrell seemed to understand.

There were a few short hisses, the snakish equivalent of a bark of surprised laughter, and then, snapped commands. "Tell woman to look away, casst sspell of ssilence, sset guardian Charm outside door. Will transsform mysself, make few sswift improvementss to your invention, give woman emergency potion sso sshe can sshield uss, transsform back before you disspell Charm. Plan will be ssafer, then."

"And am I to believe," Harry hissed, "that healer for woman truly awaitss uss?"

"Usse ssensse, boy! Ssupposse I am evil. To end usse of you here iss obvioussly not what I planned. Misssion iss target of opportunity, invented after ssaw your guardian Charm, whole affair meant to be unnoticed, hid when left eating-place. Obvioussly you will ssee persson pretending to be healer on arrival! Go back to eating-place afterward, original plan carriess on undissturbed!"

Harry stared at the invisible snake.

On the one hand, saying it like that made Harry feel rather dumb.

And on the other hand, it wasn't exactly reassuring.

"Sso," Harry hissed, "what iss your plan for me, precissely? "

"You ssaid no time," came the snake's hiss, "but plan iss for you to rule country, obvioussly, even your young noble friend hass undersstood that by now, assk him on return if you wissh. Will ssay no more now, iss time to fly, not sspeak."

The old wizard reached out toward another metal door, from behind which came a endless dead mutter, "I'm not serious, I'm not serious, I'm not serious..." The red-golden phoenix on his shoulder was already screaming urgently, and the old wizard was already wincing, when -

Another cry pierced the corridor, phoenix-like but not the true phoenix's call.

The wizard's head turned, looked at the blazing silver creature on his other shoulder, even as ephemeral and substanceless talons launched the spell-entity into the air.

The false phoenix flew down the corridor.

The old wizard raced off after, legs churning like a spry young man of sixty.

The true phoenix screamed once, twice, and a third time, hovering before the metal door; and then, when it became clear that its master would not return for all its calling, flew reluctantly after.

Professor Quirrell had assumed his true form, this time - Polyjuice only lasted for an hour without redosing - and though the Defense Professor was pale, leaning against the metal bars of the nearest cell, his magic was strong enough to seize his wand without a word, even as Bellatrix doffed the Cloak and placed it obediently in Harry's waiting hand. The sense of doom was building once more, though not in full force, as the Defense Professor's power returned, the fringes of its vast force clashing with Harry's slight childish aura.

Harry said aloud the description of his Muggle device, naming it to the observing wizard, and then a Finite from Harry turned all his hard work back into an ice cube. Professor Quirrell could not cast spells on something Harry had Transfigured, for that would be an interaction, however slight, between their magics, but -

Three seconds after, Professor Quirrell was holding his own Transfigured version of the Muggle device. A single barked word and a sweep of his wand, and the residue of glue was gone from the magical item; three more incantations later, the magical and technological were fused together as though into a single thing, and Charms of Unbreakability and flawless function had been cast upon the Muggle device.

(Harry felt a lot better about doing this under adult supervision.)

A potion was thrown to Bellatrix, and Professor Quirrell and Harry both commanded, "Drink," as though speaking in the same voice. The emaciated woman had already been lifting it to her lips, without waiting; for it was evident to anyone that this snake Animagus was a servant of the Dark Lord, and a powerful and trusted one.

Harry finished pulling the hood of the Cloak of Invisibility over his head.

A brief and terrible magic lashed out from the Defense Professor's wand, scouring the hole in the wall, scarring the huge chunk of metal that lay in the room's midst; as Harry had requested, saying that the method he'd used might identify him.

"Left-hand glove," Harry said to his pouch, and drew it forth, and put it on.

A gesture from the Defense Professor made a harness appear upon Bellatrix's shoulders, and another, smaller cloth device upon her hand, and something like handcuffs on her wrists, even as the woman finished drinking the potion.

A strange, unhealthy color seemed to come over Bellatrix's pale face, she straightened, her sunken eyes seemed brighter and far more dangerous...

...small wisps of steam were coming out of her ears...

(Harry decided not to think about that part.)

...and Bellatrix Black laughed, then, sudden mad laughter that rang much too loudly amid the small prison cells of Azkaban.

(Very soon, the Defense Professor had said, Bellatrix would fall unconscious and stay that way for quite awhile, the price of the potion she had taken; but for just a few moments she would regain perhaps a twentieth part of the power she had once wielded.)

The Defense Professor threw his wand toward Bellatrix, and an instant later blurred into a green snake.

An instant after that the Dementors' fear returned to the room.

Bellatrix flinched only slightly, caught the wand, and gestured without a word; the snake flew up and was inserted into the harness on her back.

Harry said "Up!" to the broomstick.