Thank you again for all the reviews!

Chapter Seven—Catalyst

"Why is your shirt wet, Potter?"

Severus glared at the little miscreant as Potter flinched and bowed his head. This Potter was quieter than his brother, but no less arrogant. He acted as though there was nothing he had to learn about brewing, and, given that Severus knew he had grown up in the Muggle world, that was hardly true. He spoke to Theodore Nott as though he was challenging him. He was weak and still had to take remedial lessons with Minerva but tried to hide it behind a pathetic show of strength and indifference.

Severus could have borne the boy a lot better if he had admitted to his weakness and that he wasn't perfect. But such an admission, of course, was impossible for a Potter.

"I was on my way down from Professor Dumbledore's office, and someone pranked me," Potter whispered.

"Really. And you are sure that you were not the originator of that prank?"

"No, sir! I promise! They pranked Nott, too. Shoved him down the stairs at me and then cast some kind of water charm on both of us."

"Some kind of water charm," Severus said, for the pleasure of watching the boy flush a dull red. "Who were the perpetrators of this terrible prank, Mr. Potter?"

"I'm sorry, sir, I didn't know. I didn't see them."

Severus rolled his eyes. At least the boy was smarter than to blame one of his Slytherins to the Slytherin Head of House, but Severus had seen how this Potter interacted with Malfoy. He probably would have done it if he was talking to someone other than Severus.

He said nothing about whether Potter had been the one to play the prank, though. If he had been, Mr. Nott was smart enough to see through any pretense, and the way he treated Potter the next day would confirm it for Severus. If he acted the same, then perhaps Potter's story was true.

"You did not know about the troll?" Severus demanded as he unlocked his office and stepped inside, Potter following him.

"No, sir. There was a troll?"

Potter's eyes were wide and his voice on the edge of nervousness. Severus snorted. His younger brother would have already been trying to find the troll so he could fight it. That this Potter hadn't presumably meant he was a little smarter and therefore a little more tolerable.

"Was a troll being the appropriate word," Severus murmured as he gestured Potter towards the stack of dirty cauldrons he was to scrub. "Someone killed it in a bathroom on the second floor." Killed it with such violence that Severus would have suspected some of his own Slytherin students with Death Eater sympathies if he hadn't known they were all ensconced at the feast and then in the common room or too young.

"Oh."

Potter's face had turned pale. Severus shook his head a little. A Gryffindor who isn't interested in rushing off to do daring deeds? Will wonders never cease?

"Scrub those, boy. And make sure they're gleaming by the time nine-o'clock comes, or I won't release you even then."

Severus expected some sort of protest about how Potter would miss dinner, but he only nodded and turned towards the first cauldron, studying the stains on the inside for a moment before reaching for the scrubbing brush and barrel of water standing ready. The barrel was charmed to fill with water endlessly so that Severus need not deal with refilling it or with students attempting to finish the chore early by wasting the water.

Potter didn't look at Severus as he began scrubbing, running the brush under the rim of the cauldron with hard strokes and then reaching for the scoop that lay beside the barrel. Severus watched him for a minute or two. Potter gave no indication other than slightly tense shoulders that he knew this.

He knows how to scrub. I wonder—

But Severus rolled his eyes a moment later. He found it hard to believe that Petunia Evans would have been kind to the boy, but that she had apparently taught him to scrub didn't speak of harsh treatment, only a kind of pragmatism that Severus imagined he would have used himself if he was saddled with someone else's unwanted child.

By the time he began marking the essays that badly deserved his attention, he had almost forgotten the boy was there.

Blaise looked up when Theo made his way into their bedroom, his eyebrows rising as he looked at Theo's wet shirt and the slight tear in it where the edge of a stone had caught it. At least Madam Pomfrey hadn't had to tear it more in order to heal the bruise that had formed over his ribs.

"Prank," Theo said shortly, and went to the bathroom to wash and then to the common room to eat some of the remnants of the feast that had been brought there. Part of him still would have liked to go up to the Astronomy Tower, but there was no way he was going to chance it now.

As he sat and ate a slightly stale pumpkin pasty, Theo let his mind turn, slowly, back to the events that had just happened. It felt as if a whirlwind had picked him up and deposited him in a new country, the events and memories were so blurred. But the last moments—the ones when he had reached out to Harry and Harry had accepted his friendship and asked nothing onerous of him—still blazed in his mind.

A friend. I have a friend.

It was the sort of thing Theo had hoped for without believing he would ever have in the exact same way other people did. A friend had to be someone who understood him, but there were few people who would really understand what it was to be a Death Eater's son and not turn away from him. Or, in the last year, people who would see the Figgs' abuse and not react with pity or uncomfortable silence.

Harry had accepted both. Harry was there. He was utterly committed to his own survival, yes, but to Theo's survival as well.

He saved my life. He told me right away what the life-debt payment he wanted was, and he isn't going to hold it over my head.

Theo didn't even know what had surprised him most: that he was still alive, or that he wouldn't suffer because of it.

And Harry's magic. He had taken down the troll in a way that would never have occurred to Theo, and in a way that took less effort, in one way, than an adult wizard with wand magic would have had to use, no matter how much strength it took. The adult wizard would most likely have used Cutting Curses, and had to use multiple ones, given a troll's thick skin and magic resistance. In the meantime, the troll would have been striking back, and could have killed someone. Harry had simply stepped around the problem and used his magic in a way that the troll's abilities couldn't protect it from.

Theo realized he was smiling, and Crabbe and Goyle, who sat in the chairs across from him right now, were giving him uneasy looks. He bit back the smile as much as he could, content to bask in his own memories.

Harry was cold and calculating—in a way. He would follow the Gryffindor image and do what his parents wanted from him—in a way. He was Theo's friend, and there was no "way" about that, it was simply true.

But most of all, he wasn't arrogant. It wouldn't occur to him to carry himself as above others, at least not right now, no matter what kind of magic he had that they didn't. Theo thought Harry could stand to work on his pride a little, but arrogance was something he would happily help Harry avoid.

All his life since he'd really begun to understand history, Theo had accepted he would follow his father into the Dark Lord's service. The determination had only hardened after the Figgs took him away from his father and tried to force him to convert to their side.

Now, though…

Maybe I've found my own lord. A better one.

Harry didn't come back to their room until it was almost nine. Felix was on his feet in instants and running to meet his brother. Harry blinked, looking a little unnerved as the bedroom door fell shut behind him.

"Felix?" he asked.

"Where were you? You weren't at dinner and there was a troll in the school and I didn't know where you were!"

"I had detention with Snape." Harry's eyes were still wide, and he moved as if he thought Felix was going to whip out his wand and curse him. "Remember? He assigned it in class today. At six, so I'd miss the Feast."

Felix swore and collapsed back against the wall. He hadn't remembered. He didn't have a perfect memory for things he heard, just things he saw—mostly things he'd read. And Harry had said something about it, he thought, but he'd been talking to Ron and then they'd played chess and then one of the third-year girls had come bothering him about whether he remembered facing Voldemort on that Halloween ten years ago and—

He'd just forgotten.

"I'm sorry," he whispered. "It must have been scary. Are you all right?"

"I actually never even heard there was a troll in the school." Harry shook his head. "Professor Dumbledore wanted to talk to me about how things were going, and then on the way down from his office to Professor Snape's detention I ran into Nott, and then some people we didn't see pranked us—"

"How did they prank you?"

"Sprayed water at us and tried to shove us down the stairs. Nott fell and bruised his ribs a little, so he went to Madam Pomfrey. But I didn't fall."

"Who were they?" Felix scowled. He would go and bring down the wrath of the Boy-Who-Lived on them so hard. People shouldn't mess with his brother just because he was a firstie or he was weak in magic.

"Didn't see them." Harry's mouth flattened out, as if he was angry about that, but didn't know what to do. "Who knows? They could have been Slytherins, or Hufflepuffs or Ravenclaws for all I know."

"They could have been Gryffindors, too," Felix said reluctantly. He didn't want to make it sound as if their House was full of idiots, but, well, some people were idiots in every House. And other people weren't idiots but used their intelligence the wrong way, like Percy Weasley. "Maybe they were trying to get Nott and they got you. Or maybe they think—sorry, maybe they think you're costing us points because of the remedial lessons."

Harry took a deep breath. "Even though Professor McGonagall never takes points from me?"

"Yeah, sorry. I just—some people are idiots."

Harry's smile flashed then. "Yeah, you're right."

"Oh!" Felix abruptly remembered the conversation he'd wanted to have with Harry after Charms the other day, but which he hadn't because they always seemed to be surrounded by other people. Well, right now everyone was distracted by the feast that had been set up in the common room. "I wanted you to know that you don't have to practice spells on your own. The way you were doing with Charms? You can practice with me. Especially now that you're still struggling with Transfiguration, and I'm good with Transfiguration."

An odd expression crept over Harry's face for a second, and then he nodded. "Okay. But, Felix…well, sometimes I have to practice on my own."

"Why?"

"Because I get tired of failing in front of other people. Because you're good at it, and I'm just—not."

"I won't poke at you or anything." Felix said it softly. He could see how Harry was ducking his head and turning away. He must be thinking of what Mum and Dad would say if they could see him now, and thinking Felix would say the same thing. "I know it'll take a while. You got Charms and Defense. Transfiguration's harder. You just need some help. I want to help you."

"You already are, though."

"How?"

"By sending the owl post and things like that, so I don't have to interact with Hedwig or go to the Owlery." Harry rubbed the back of his neck. "By being friendly and including me in your conversations with Ron. By standing up for me the other day when Granger got a little overbearing."

Felix snorted. He liked Granger as a person and thought she was really smart, but she still didn't know how to make friends. "A little overbearing" was stretching it, even. "Well, I want to do more than that."

"Look, Felix, it wasn't your fault that I got stuck with Muggles for ten years."

Felix felt as though Harry had punched him in the stomach. He coughed and said, "It wasn't—it isn't about that."

"Isn't it?" Harry gave him a highly skeptical glance, his eyes shining green and then red for a second in the firelight. Felix wondered absently if Muggles' eyes did that on a regular basis. "I think it is. Anyway, Mum and Dad apologized for that. So you don't have to worry about it."

Felix twisted his hands awkwardly together for a second. He wanted to defend Mum and Dad, but he thought what they'd done was wrong. He wanted to say that he could still help Harry, but Harry had refused his help.

In the end, he said the only thing he could think of. "I know you missed the feast. There's still food downstairs. Want some?"

Harry gave him an uncertain smile. "If you're going to be there? Sure."

Felix was glad, as they left the bedroom and went back down to the common room, that some things still made sense.

Harry had lain awake in bed for hours before the first sob worked its way up his throat.

Harry rolled to the side and turned his face into the pillow. He flicked his hand, not bothering with the wand when he was the only one there to see, and the equivalent of the Silencing Charm closed around his curtains.

He might have to cry, it might feel as though the sobs were forcing their way up through his chest like piercing lances, but no one had to know about it. No one had to know how weak he was.

"Did you think that you could get away with it?"

Harry had known that going back to Quirrell for a lesson after the death of the troll would be hard. He had gone in with his back hunched, his magic gathered under his skin, as he was learning to keep it constantly after his constant need in Charms and Defense to be ready to perform a "spell" with his "wand." But he hadn't known what that voice full of cold fury would sound like.

As it was, he ground his teeth and said only, "The only thing I cared about then was surviving."

Quirrell spun around. He'd been facing the far wall of his office, and when he turned, the impact of his rage-filled expression was like a blow, but still better, somehow, than facing the back of his head.

"Why were you near the troll at all? Why were you not in the feast with the rest of the stupid children?"

"Snape assigned me detention, but Professor Dumbledore wanted to see me before that. I was on his way down from the office when I ran into the troll."

"What did Dumbledore want to see you about?"

Harry stared at him in silence.

"Answer me, boy."

"Why in the world would you think I'd answer you?" Harry snarled softly, watching the way Quirrell's eyes widened. He could feel his magic humming under his skin, edging more and more towards coming out. For some reason, though, he didn't feel like calling fire, even though it was the thing he could do most easily. It was—it was as if his magic had tilted towards water after the encounter with the troll. He could sense water in this room, somewhere, and he could reach out to touch it. If he touched it, he could use it.

Killing the troll had killed something in him and scarred something else, but it had awakened something, too. Harry knew he still needed to pretend around most people. They wouldn't understand, or they would be able to kick him out of Hogwarts and back to the Dursleys if they wanted.

But around people who knew better, like Quirrell, Harry thought, I can kill people now. I could do it again if I had to.

"Your magic," Quirrell whispered. "What did you do?"

"I thought you knew perfectly well what I did. I thought you were going to punish me for it."

"Not the troll. The troll is a minor detail. What did you do?"

Harry didn't have any idea what he was talking about, but that was probably a minor detail, too. He kept watching Quirrell, and his magic kept watching Quirrell.

Maybe that was what the professor meant. His magic had awakened, too. It had teeth and claws, and it crouched on Harry's shoulder like the owl he would never be able to have, watching everything and everyone around him. The only person it relaxed around was Theo. Harry thought that made sense. Theo was his friend. Theo kept his secrets. And Theo had been important enough for his magic to send that vision, so that must mean his magic liked Theo.

"You have no idea what you did, do you?" Quirrell finally asked, sounding resigned. He rubbed his hand across his face, a gesture Harry had never seen him make, and sighed. "I wish that elemental magic was not so little understood."

Harry chose not to answer that, either. Maybe what he had done was bad—bad for his magic, not morally bad, which Harry was more inclined to worry about right now. But he would still take the ability to protect himself over not having done anything to it.

And if he hadn't battled the troll, he would have died, and Theo would have died. Maybe other people.

"Did you intend to drown the troll?" Quirrell finally asked, sounding a little exhausted.

Harry thought about the question and decided that it couldn't do much harm to answer it. "No, sir. I wanted to knock it unconscious by having the water slam its head into the wall."

Quirrell nodded, his eyes distant. "That may be part of the reason for the change in your magic," he murmured. Then he abruptly started and clapped a hand to the back of his head. "Leave me now, Mr. Potter. We will skip the lesson for tonight, and I will contact you when I am ready to resume them."

Harry half-shrugged and slipped out of the room, although he made sure never to turn his back completely on Quirrell until the door fell shut behind him. His magic gripped his shoulder with invisible claws and looked around alertly.

That was another change. Harry found himself awake if one of his roommates woke up during the night, even if they were able to creep around quietly, like Neville did. He knew when someone was moving towards him, him specifically, around the Gryffindor table, while his magic didn't react if someone was aiming for another person. The Weasley twins had seemed a little startled when Harry turned to face them before they announced themselves in a corridor the other day.

But it was a change Harry rather liked. He wouldn't have to jump or flinch from loud noises and sudden sounds if no one could get close enough to him to make those sounds without him knowing about it.

He had promised to go back to the Gryffindor common room to work on the next Charms essay with Felix, and it was probably best he did that instead of what he wanted to do, which was go and meet Theo in the library. Felix seemed to be paying more attention to him since Halloween, and he kept offering help in class if Harry wanted it. It would keep him happy if Harry worked with him instead of staying away for an evening.

Harry half-wished that he could just tell his brother the truth and didn't have to handle him the way Aunt Petunia had sometimes handled Dudley and Uncle Vernon. But he had too many secrets to do anything else.

Albus leaned back in his chair and met first James's eyes, then Lily's, then Sirius's. "I know that we have no absolute proof of what happened to the troll—"

"Or who let it into the school in the first place! I think that's the more important thing!"

Albus smiled a little and raised his hand. James had always been volatile. "I believe I have that situation under control. But I do want you to consider the fact that it could have been Harry's accidental magic that killed it."

Lily sucked in a sharp breath. "You—you think so?"

"Yes. It has all the signs. The spells that would release water from the loos and the sinks in the way that happened in the bathroom would have released it in a different pattern. This was wild and sloppy. And the drowning of the troll was entirely by accident, I am sure. There is every sign that Harry was fighting simply to hold it in place. It flailed around and left, well, quite a bit of blood and bone on the walls and floor. If he had meant to kill it, he could simply have aimed a stream of water down its throat."

"Unless…"

"Yes, Sirius?"

Sirius's eyes were dark. "Unless he did mean to kill it, but he just didn't have enough control of his magic to do it."

"We do have to consider that possibility, unfortunately. And the wild escape of water from the pipes and the sinks might suggest it."

Albus sighed silently to himself. He had no idea why Harry's accidental magic had developed the way it had. While the boy had undoubtedly suffered at the Dursleys' hands—a burden for which Albus would carry the guilt until they buried him—he did not bear the scars or the reflexes of someone for whom beatings had been the constant scourge of life. Accidental magic could be the kind that lashed out for children like that, but Harry was not in that category.

And yet, Harry's magic was wild and focused on offense in any case. Albus had no idea how Harry had ended up in the bathroom with the troll, nor why he would have tried to kill it instead of running or delaying it.

Lily raised Albus's next thought before it could finish fully forming. "Maybe he tried to use the water to pin it into place, so he could get away. There's no saying that he stayed there while it died."

Albus nodded, relieved. "Yes, that's also a possibility, Lily. He tried to defend himself. The water exploded from the pipes. His impulse was to run, but the troll turned towards him, and in his fear, he wanted to stop it. His magic understood the stop it order as killing the troll, while Harry himself probably only meant to keep it there."

"Is that really better?" Sirius demanded. "It means that he has even less control than you thought he did."

Albus grimaced. He had been cheered at first, along with Lily and James, when it seemed as though Harry was gaining control in Charms and Defense, but he suspected he knew what was happening now. Harry wanted so desperately to succeed, so desperately to please his parents and become a powerful wizard, that he was forcing the magic through the wand with an effort of will.

That was a far cry from the proper control that he needed, that Felix had always had. And it was a far cry from being able to tell his magic what to do and have it obey. It meant that it would remain accidental, flailing, reaching out and accomplishing Harry's will with clumsy giant fingers.

It might hurt someone else. It might kill them.

Albus wondered if he would know when the time had come to remove Harry from Hogwarts for the safety of others. His mind flashed back to the damage an Obscurial might do, and while Harry was not one of them, his magic would not flow through a wand and was not leashed. A feral, snarling thing, it might grow even worse now than Harry had faced down a troll. It might assume that killing was an acceptable response.

"What can we do?" Lily whispered. "It was partially our fault that this happened…"

"We didn't have a choice," Sirius said. "Not after."

He didn't have to finish the sentence. All four of them sitting in the office knew he meant after that night.

"I will place some monitoring charms on Harry," Albus murmured. "They would give me warning if he gathered his magic to do something that reached the level of killing the troll. I would be able to arrive and contain him."

Lily bowed her head. "I couldn't live with myself if Harry killed someone, Albus. Or hurt them, in the process of trying to protect himself. If we could only make him understand that he isn't in any danger at Hogwarts."

Albus nodded. It was Felix who might be, but so far, Albus had sensed no sign of Voldemort's wraith, as he had thought he might be once the professors learned of the presence of the Philosopher's Stone. He had wards that would detect any possessed animal, any sign of a Dark spirit attempting to force entrance.

And he was sure that was all it would be. If Albus was right about the ways Voldemort had secured his immortality, the wraith would not have enough strength to possess a human being.

"I will also speak with Harry more regularly. Access to a trusted adult would not go amiss. You know that Harry doesn't—have them right now."

Albus winced at speaking such words to Harry's parents, but they were facts, and Lily and James's answering smiles were bitter but understanding. Lily more than James's, truth be told. James had cherished a hope that Harry would simply fit seamlessly into their lives, Albus knew, the way Felix did.

But Harry was a casualty of politics, and it would not be that easy. Albus hoped that Harry would blend more easily with his family in the future.

For now, he had to keep Harry from causing any more casualties of his own.

"It was hard for you to come here?"

"Hard to get away from a brother who's suddenly decided he's my babysitter," Harry said, glancing up briefly to roll his eyes in Theo's direction before he turned back to the book open under his hand.

Theo blinked when he recognized it. "Why do you want to read children's stories?"

"I'm hoping there'll be some indication in here why my magic suddenly feels like a dangerous beast. It's not something I can exactly ask anyone about, and the research I've tried to do on it is—no good. I don't know the right way to search for it. Plus, I don't want anyone to know I'm doing it, which pretty much means I can't ask for help. But children's stories might reveal something about people with magic like that. Or elemental powers. Or at least what people believe about them."

Theo blinked carefully and sat down across from Harry. "Your magic feels like a dangerous beast?"

"Since Halloween. It feels like it's always awake and aware and ready to swipe at someone if I want it. The Weasley twins haven't managed to sneak up on me the way they used to. No one sneaks up on me anymore."

Theo stared some more, looking carefully for disturbances in the air around Harry or anything else that might support what he was talking about. "I don't see any sign of it."

"Well, it likes you, doesn't it."

Theo coughed. "Excuse me?"

"It relaxes when you're around me. It's like having an owl that just went to sleep on my shoulder." Harry waved his hand. "Look, I don't know how else to describe it. That's one reason I'm trying to find out, because this is weird, and I don't know if it's because of what happened on Halloween or what I made happen."

He killed. Still, Theo had grown up with two people who had caused multiple deaths in the war, and they had never told him their magic felt like that.

Maybe it had to do with Harry's magic being wandless and elemental. Theo had to admit that it was all a bit bewildering to him, this new world that had opened up in front of him because he had become Harry's friend. He had never heard of half the things that it seemed Harry carried around on a daily basis.

But it made him feel as if he had opened his eyes on a bright morning, too. Because he was otherwise bored at Hogwarts most of the time, and here was someone who wasn't boring.

"Why did you manage to find me before something happened?" he asked then, keeping his words vague in case someone was listening. He really had to try and figure out some good privacy charms as soon as possible. "You weren't anywhere near me at first, were you?"

Harry hesitated and looked up. Theo knew, before Harry opened his mouth, what he would say.

"Don't," Theo interrupted harshly. "Don't put me off with stupid words or meaningless platitudes. I want to know."

"It's going to sound weird."

"This, of course, is an experience I have never had around you."

Something strained and watching melted from Harry's face, and he gave a half-laugh. The sensation of possibility and future expanded in front of Theo, and he smiled back.

"I had a headache when I came out of Dumbledore's office, and some white speckles in my vision," Harry admitted. "It was like what happened that day in Potions when Longbottom's potion spilled—"

"Which one?"

"The Boil Cure. I saw a gout of potion come out of the cauldron. That's why I jumped up on the stool. Then when the potion actually came out and soaked Longbottom, I thought it was the second time and no one else had seen the first one. And now I know, no one did. I was the only one that did." Harry hesitated. "I saw a vision of you, dead, with your chest caved in. And my magic started pulling me towards you. So I ran."

Theo half-bowed his head. Yes, the news of Harry's visions was at least as startling and rare as the news that he was an elementalist capable of mastering all four elements. But the news that the vision had focused on him, and more, that Harry had cared enough to run to Theo's aid instead of running off and hiding somewhere the way Theo probably would have—

He couldn't breathe for a long moment. He had a friend.

When he got his breath back, he teased, "So you really are a Gryffindor."

Harry did his half-laugh again, and it warmed Theo down to his bones as he started suggesting some things they might be able to look up in the library to find out why Harry's magic had changed.

When Theo had left, with a wave, for dinner, Harry quietly drew out the book that he had tucked beneath the book of children's stories when his magic told him Theo was coming. It was a book of wizarding law as it related to children and caretakers, and Harry didn't understand half of it, but he planned to read it over and over again until he did.

Actually, it probably wouldn't have mattered if Theo had seen it. He would have assumed Harry was researching some way to make sure that he didn't have to go back to the Dursleys.

But Harry didn't want to raise Theo's hopes by telling him how intently Harry was working to find some way to get him away from the Figgs. Harry might not be able to do it. He would hate to see the crushed look of disappointment on Theo's face if he promised that, and then—couldn't deliver it.

But at the same time, Harry was determined to do it. He had to do it. He couldn't leave Theo to suffer with the Figgs one moment longer than necessary.

Theo was his friend. Harry had already saved his life from a mountain troll.

Begin as you mean to go on.