Ginny Weasley was groggy when Madam Pomfrey got her up; she had not slept well. Her classmates would continue to sleep for another half an hour; she was being woken up early to compensate for the time she would lose transferring to her proper dormitory.

"You're good to go," said Madam Pomfrey. "You're keyed into the wards so that you can enter any girls' dormitory in the school. Don't worry about the lavatories; there aren't any gender-based wards placed on them in the first place, in case of emergencies. And we just checked to see if you're being possessed by any Dark Lords. Rest assured, you're not. Oh, and you got an owl from your mother." She handed Ginny a letter and started away, but stopped and turned around. "If anybody asks why you were here, tell them you had an allergic reaction to the interior of the Sorting Hat." Then, she left.

Ginny examined the letter; it was the distinct red color of a Howler. Well, then, she'd better open it now, in the privacy of the Infirmary, rather than waiting until she was in a more public place. Despite their nickname and reputation, Howlers weren't always sent in anger as a punishment. Sometimes, they were simply the magical equivalent of voicemail, used for messages that it was determined needed the precise inflections of speech. Nevertheless, they had a reputation for being loud and embarrassing to listen to within earshot of others. Ginny ripped the seal on the envelope, and the letter unfurled and floated in the air in front of her, and began to speak in her mother's voice:

"Ginny! I'm so sorry if I gave you the impression you had to go to Gryffindor. I'm not disappointed or upset at all. I am a bit surprised, though, of course, for obvious reasons. I didn't actually hear about your Sorting from you first – a few of your brothers wrote home about it too. But don't worry that it means that you're Dark, or we won't love you. Ginevra Weasley, you are a great witch, and I know that you will accomplish great things. You have a great sense of right and wrong, too, and you don't need to go to Gryffindor House for that. They say the winds are changing and Slytherin House might come out much better than it has been during my life. As for the other thing... I'm not going to say it out loud, because it is very much a secret, which nobody should know about. But don't worry about that, either. It was a bit of a surprise for me to hear about that, too, but not a complete surprise. Because the truth – which I should have told you about much earlier, but I never thought to, sorry – is that that's a Prewett family secret. Some of us can do that. I can't, neither of my parents could, none of your brothers can, as far as I know. But sometimes it happens. I believe your uncle Gideon could, when he was alive. Use that talent for good if it ever comes up, but stay out of trouble with it if it doesn't. Don't stress, make good grades, and have fun! I love you! Goodbye, Ginny." And the letter made a puttering sound, and ripped itself into shreds and went up in fast-burning magical flame. Well, that answered some questions as happily as she could imagine them being answered... but Ginny doubted she would send her mother a follow-up letter asking why her soul was recognized by the wards as a boy.

Soon, Ginny had packed up all of her supplies and was ready to move into the Slytherin Girls' Dormitories. On her way downstairs, she was met by her brothers Fred and George, who were also up early. They cheerfully hissed at her.

"Very amussing," said Ginny.

"Ooh, you hiss better than us," said Fred.

"Did they teach you that in Slytherin?" said George. They showed no sign of comprehension, confirming her mothers' claim that her brothers could not speak Parseltongue, and she tried to smile. Deep down, she still had not forgiven them for whatever mystery prank they had pulled last year (or at least that she suspected them of pulling), to get a news story printed that she was engaged to Harry Potter. The point of the prank was that it was a joke, a thing ridiculous on its face, that there was no way on Earth that Harry could wind up with Ginny Weasley, of all people. She had barely been the butt of the joke at all; the real victims were Rita Skeeter and the Daily Prophet. But she had still been a butt of the joke, and it had been a very cruel joke. They knew how she felt about Harry, everyone teased her for it, especially Fred and George, who took every opportunity they could to tease anybody.

"So are you applying to run a first year army?" said George.

"Or are you too busy getting your Dark Mark done?" said Fred.

"Ron's absolutely certain he's going to be one of the second year generals," said George.

"Wouldn't count on it if I were him," said Fred. The structure of Hogwarts' Defense class was very different this year. In honor of Professor Quirrell (also known as Professor Monroe), much of the class's curriculum would be taught by the seventh year generals, who had been selected over the summer, in vast independent study sessions. The seventh year generals would also pick three generals each from each of the six lower years, and each year would fight battles similar to those arranged by Professor Quirrell. The only rule on who could be selected as a general (besides that all generals needed to apply voluntarily) was that no one could be a general in two consecutive years. The actual Defense Professor, Gilderoy Lockhart, had some authority, but was more of a supplementary guest lecturer on Special Topics In Battle Magic than the true leader of the class. The true leader of the class was the still-burning spirit of Professor Quirrell.

"I might sign up," said Ginny. "I might not. I have a lot on my mind."

"Slytherins always have a lot on their mind," said George.

"You can see it in their eyes," said Fred.

"They're deciding who to help – for now," said George.

"Who to screw over," said Fred.

"How to best get their way," said George.

"How to best prevent their enemies from getting their way," said Fred.

"Ambition and cunning, those are the Slytherin traits," said George, but Ginny had already walked away. She didn't want to hear any more.

The next human being Ginny saw was Draco Malfoy, who was arguing with his House Elf about something.

"These are completely useless," said Draco, holding up a stack of papers with something illegible scrawled on them.

"Dobby is very sorry!" said Dobby, who was crouched on the floor, holding onto Draco's leg. "Dobby will do better next time!"

"No, I'm not sure you will," said Draco. "I'm not sure you understand what you did wrong. I told you to write notes on all of my schoolbooks, that I could study. Maybe that was a mistake. This is illiterate gibberish about the bindings, types of paper, fonts, formats... Absolutely nothing about the content."

"Dobby did best Dobby could," said Dobby. "Dobby is very sorry that that was not good enough."

"Dobby," said Draco, "can you read?"

"No, sir!" said Dobby. "House Elves are not allowed to learn how to read, for fear that we might launch a rebellion against the wizards! We can only read and write in shorthand. If we try to learn the regular way we shrivel up and die."

"Oh, well," said Draco, sarcastically, "I'm glad we cleared that up beforehand. Why didn't you tell me you couldn't read when I asked you to?"

"Master told Dobby to look through his books and take notes for Master to study," said Dobby, "and Dobby did his best." At this point Dobby was trying to grind his head off with the floor.

"Stop!" commanded Draco, and then his attention changed. "Ginny! I didn't notice you." He gestured for Dobby to go to his room, and he teleported away.

"Hi," said Ginny. "It sounds like you're having some House Elf trouble."

"Yeah," said Draco. "He's been in my family for my whole life, but I'm not quite used to ordering him around. I only just inherited him, when-" He stopped, and choked up.

"I heard," said Ginny. "My condolences."

"And when Mother reappeared, she decided to let me keep him," said Draco.

"My family doesn't have one, so I wouldn't know where to begin to help you," said Ginny. "My parents say it's wrong to keep House Elves, but they can't even afford one, so what would they know?"

"I think that it was wrong to make House Elves, but now that they're here, what are we going to do?" said Draco, "Commit genocide?"

"That's exactly the line of reasoning I've taken up," said Ginny.

"Yeah," said Draco. An awkward pause. "Oh, um, by the way... I noticed your problem last night. I wouldn't be surprised if someone else noticed, but I'm not going to tell anyone about it."

"Okay," said Ginny.

"It's a common enough problem, and it's not your fault," said Draco. He decided not to add "and I have no interest in destroying you."

"Thank you," said Ginny. She decided not to add "I worried about that all night."

"You seem like the kind of person I'll be interested to get to know," said Draco. "You're not like any other Weasleys I've met. I think the Sorting Hat was right to put you in Slytherin."

"Thank you," said Ginny, and she smiled.

"See you around," said Draco.

Ginny arrived in Charms class after she had selected her bed in the Slytherin Girls' Dorms, and placed her books and supplies beside it. "Selected" might not be accurate terminology, seeing as there was only one bed left, between Pansy Parkinson and the wall. But she was sure she would soon acclimate to her new home; it was certainly better than the Infirmary.

Professor Flitwick tapped on his glass with a spoon to get the class's attention.

"Good morning!" cried the Professor.

"Good morning, Professor Flitwick," said the class, half excited and half asleep.

"I'm sure you're all very excited to finally begin performing magic of your own," said Professor Flitwick, "but we will begin with basic Charm theory. Can anybody tell me what a Charm is?"

There were no Hermione Grangers in the class that day.

"A Charm," said Professor Flitwick, writing on the board, "is the opposite of Dark magic. Now, can anybody tell me what Dark magic is?" Colin's hand shot up.

"Yes, Mr. Creevey?" said Professor Flitwick.

"It's bad, evil stuff bad, evil people do!" said Colin. "It's stuff what hurts people."

"One point to Slytherin for an honest attempt," said Professor Flitwick, "but incorrect. Correct in the general vernacular, but not in an academic context. Can anybody else tell me what Dark magic is?" Nobody could. "Dark magic is magic that cares about your intent to cast it. A Charm does not."

Everyone frantically scribbled down notes copying what Professor Flitwick had written on the board; it screamed "quiz question".

"I'm not sure where the idea that Dark magic was evil and Charms were good came from," said Professor Flitwick. "Personally, I blame the Patronus Charm. It's not a true Charm – it's some of the Darkest magic out there. But it's very much associated with 'the good guys', perhaps for good reason. And then we have all sorts of tyrants going around calling themselves Dark Lords, for various reasons I find too morbid to discuss. But the truth is that, in a theoretical sense, Dark magic is magic you need to mean to cast, and Charms are magics that simply do not care what you mean. You will perform both at Hogwarts."

"Of course, it's a spectrum," continued Professor Flitwick. "Many Charms have Dark qualities, and all Dark spells have Charm-like qualities. But there are many misconceptions about what these things mean. Dark spells are not more dangerous than Charms! Dark spells are more likely to be designed as weapons in the first place. But a Charm can be much more dangerous than a Dark spell, because you can cast it without thinking about it! Many wizards will simply never be able to muster the malice to cast the Killing Curse, or many other Curses. But they will be well-able to cast Charms, in combat, to kill; most commonly with Diffindo, the Severing Charm, which will sever arteries just as easily as it severs vines."

"Furthermore," said Professor Flitwick, "Charms are more dangerous to cast than Dark spells, because they do not care about context, they only care that you have fulfilled the terms of the spell. Let's take a simple example, Wingardium Leviosa. Do not take out your wands, I am merely speaking about the spell. Wingardium Leviosa, the Levitation Charm, may be modeled as a simple logic gate." He illustrated the concept on the board. "If you say the incantation correctly, and make the correct wand movements, the target will float – or, more accurately, I suppose, the Charm will try to use some of your magical energy to make the target float; it won't do any good if the target is too large and your magic is too weak. If any of the conditions of the logic gate are not met, the Charm will not recognize it and the target will not float no matter how strong your magic is or how little energy is needed to levitate it."

"A student once asked me, 'if I point at the wrong object, will the spell apply to the correct one?'," said Professor Flitwick. "I cannot imagine what possessed him to ask such a question. No. If you point at the wrong object, the correct object will not levitate. The wrong object will levitate. The Charm does not care what you wanted to do. It only cares what you did."

Garbage in, garbage out, thought Colin Creevey, who had briefly studied programming before learning of the existence of magic.

"Some Charms are more complicated," said Professor Flitwick, "and have multiple parts, which act as multiple logic gates. For example, Scourgify, the Scouring Charm, requires the proper incantation and a series of three wand movements. If the incantation is incorrect, the Charm will not be activated at all. The first wand movement performs the first part of the charm, which summons soap and water. The second wand movement performs the second part of the charm, which actually cleans the target. The third wand movement performs the third part of the charm, which dispels the soap, water, and detritus."

"The multipart nature of such Charms allows for complex failures with complex results," continued Professor Flitwick. "If the first wand movement is failed, but the rest of the charm is performed correctly, there might be some slight effect on the target, but not a significant one, because the soap and water are necessary for the Charm's functions. If the second wand movement is the only point of failure, on the other hand, then soap and water will briefly manifest but will do little. A failure in the third wand movement will leave the soap, water, and detritus in place, potentially further complicating one's cleaning needs."

"As I said, many Charms have Dark components," said Professor Flitwick, "and all Dark spells have some Charm-like qualities. Most notably, many Charms have a safety feature wherein basic knowledge of the Charm's function is part of the requirement for the Charm to activate. This is technically a Dark safety feature, and blurs the line between a Charm and Dark magic. We would all be better off if more Charms were designed with such features in mind, but you cannot count on them. Never use an entirely unknown Charm except when you are being supervised by someone who does know its function and has instructed you to use it. When using a Charm of which you have vague awareness, do not be surprised if you run into complications originating from your gaps of knowledge. Ignorance of a Charm is no excuse, and a Charm works precisely how it works, not how you expect it to work."

"A Charm is not intelligent," concluded Professor Flitwick. "You are intelligent. A Charm is a law of the universe. It has been there as long as anybody can remember, it will be there forever so far as we can predict, and it will not move to accommodate you. It will only move in its own way, and you must use your intelligence to decide when to exploit that. By next class I want a full-scroll flowchart where you tell me how to determine what I am doing wrong if I am attempting to cast Wingardium Leviosa on my chalkboard and it is not raising. Class is dismissed early, and I advise that you all take a nap."

Ginny followed the rest of her class to the dormitories, and on her bed, she considered Draco's House Elf problem in terms of Professor Flitwick's short Charms lecture. It occurred to her that, while the core of a House Elf's brain undoubtedly ran on pure Dark magic – it wanted nothing more than to do exactly what its Master wanted – most of its brain probably operated through Charms, unable to do anything but what it was told, using only information it knew in patterns it knew. In fact, Dark magic could all ultimately be reduced down to Charms – Charms where the condition of their action is a feeling in someone's head, but Charms nonetheless. By extension, all brains were in a sense entirely reducible to logic gates – but what would that mean? Ginny didn't want to think about it.