To the moon-struck crystal phial, add one of your own hairs, a silver teaspoon of dew collected from a place that neither sunlight nor human feet have touched for a full seven days, and the chrysalis of a Death's-head Hawk Moth. Put this mixture in a quiet, dark place and do not look at it or otherwise disturb it until the next electrical storm.

• • •

The Death's-head Hawk Moth chrysalises had been easy. While usually expensive, Sirius' Uncle Alphard was a friend of a friend of a Potions supplier, and Sirius' Uncle Alphard was also not the type to ask questions (although he did seem to be under the impression that Sirius was attempting a love potion, from the Ashwinder eggs and rose thorns he included in the package). At any rate, a rather musty-smelling bundle had arrived at James' window in the August after third year, and the contents had been safely stored away in his trunk ever since.

The dew, on the other hand, had been a problem. They had tackled that part of the project back in April.

On the Hogwarts grounds, there was only one place where neither sunlight nor human feet dared go. For a while, James, Sirius, and Peter had debated the necessity of going there. Sirius suggested Conjuring the dew—after all, surely there was no sunlight or human feet wherever Conjured things came from—but James and Peter had agreed this would be cheating. And cheating was not something they could afford to risk.

"If I get stuck as part rhinoceros or something forever and it's your fault," said Peter, narrowing his eyes at Sirius, "I swear I will stampede you."

"I'll be half a golden lion tamarin and sit in a tree laughing at you," said Sirius off-handedly. "Also, you need more than one rhino for a stampede, Pete. Although, mind you, I've always thought Davy Gudgeon had a rhino-ish look to him. Perhaps you could get him to help."

Peter colored. Davy Gudgeon was in Hufflepuff, and the sort of person Peter might have become if he had never met James, Sirius, and Remus. Sometimes James thought his best friend went a little far in teasing Peter.

"Nobody's going to be a rhino or a tamarin," said James. "That book said people are normally boring things, remember? Like a rabbit, or a crow, or… or a newt. I bet I'm a newt."

He didn't, of course, but he thought it would make Peter feel better, and it did.

• • •

Ultimately, there was no hope for it. In muttered conversations while Remus' attention was elsewhere, and in those hours when he was too ill to leave the hospital wing, James and Sirius agreed: they would have to go into the Forbidden Forest and find the centaurs.

Some of the books theorized that the Animagus Charm had come from the centaurs in the first place: that was how they had become the way they were. James didn't think this theory held much water, but it was true that centaurs had magic that wizards didn't, and that a great deal of that magic came from nature. He had found a book that described the way centaurs burned herbs to divine the future, shot arrows to determine the course of their lives, and collected dew in earthen bowls. If anyone knew how to go about this part of their project, they did.

Apparently, though, centaurs didn't like wizards much. For that reason, James, Sirius, and Peter decided that they would enter the forest wearing the Invisibility Cloak. It seemed like a good idea anyway—James had heard all sorts of stories about the things that lived in the Forest, and while he and his friends had made several furtive explorations along the edges, they'd never gone all the way in. Sirius claimed most of the stories were just rumors—and after all, they had a friend who was probably more dangerous than any of the creatures who lived there—but James wasn't so sure.

The night after the full moon, when Remus was still in the hospital wing, the three boys slipped on the Cloak and snuck out of the castle. Sirius lit his wand, and a whispered Point-Me took them toward the center of the Forest, where Hogwarts, A History explained the centaurs had settled long ago.

"You sure the book was right?" whispered Peter, crunching twigs from beside James. "That they sleep during the day, I mean—so they can look at the stars at night? And if it is right, then doesn't that mean we'll be disturbing them? Won't they be upset?"

These were all valid points, considering the book they had consulted was at least a hundred years old, but James pretended not to notice. "We've always figured things out before. Don't worry so much. We're going to charm the pants off them."

"But centaurs don't wear pants—"

Peter stopped abruptly. Something bulky and yet graceful had moved in the copse of trees ahead of them. Its eyes glinted in the darkness, and it stopped too, looking straight at the place where the Cloak hid their group. James' breath caught in his throat.

"Who goes there?"

The voice was male, and deeper than most. As it spoke, it came fully into view, the long tail on its hindquarters whipping back and forth in agitation. James took in four enormous, seal-brown horse's legs, cascading waves of smooth dark hair, the place where the horse became a man, rippling into the kind of muscles that James was quite sure he would never have. There was also a look of fierce suspicion written upon the creature's face.

Purely on instinct, James tore the Invisibility Cloak away, revealing their totally unimpressive status as skinny, dirt-covered fourth-years, clad in jeans and dressing gowns. He held up both hands, hoping it was the right thing to do. "We're only students," he said carefully. "I'm James Potter, and this is Sirius Black and Peter Pettigrew. We, er—we brought you something."

The book had said that the centaurs might be more amenable if you brought them a gift, that their resentment against wizards was such that they considered even knowledge a reward that they didn't deserve. At least, not for nothing.

Sirius held out an assortment of Alihotsy branches, which Peter had tied with a red and gold ribbon. ("My mum always says presentation is everything," he explained.) They'd been careful to choose a plant that wasn't endemic to the Forest—Alihotsy trees grew only in Africa and in carefully-curated Greenhouse Six—and that the centaurs might have some use for. As Alihotsy branches were a necessary ingredient in Laughing Potions, James hoped they might cheer the centaurs up slightly.

The centaur before them plucked the branches out of Sirius' arms, sniffed them for a second, and then threw them on the ground in disgust.

"We have no use for your foreign plants, human. The arrogance of your kind is such that you believe whatever you offer us will be greeted with grateful thanks—indeed, with praise and celebration. The truth is that we have all we need in our Forest. It is your kind's meddling that puts our way of life at risk." He paused a moment, and James felt his dark eyes boring into his own. "Come this way."

Sirius gave James a searching look, and they nodded tersely at each other, taking careful steps behind the centaur. Unease radiated off of Peter, who was making sure to walk between James and Sirius. The centaur took them between the trees, through brambles and bushes and vines. The journey scraped up their bare hands and embedded thorns in the soles of their shoes. At last, they arrived at a clearing, where four centaurs with their backs to them were looking up at the stars.

"Mercury," murmured one. He was smaller than the others—a child, James thought.

"Yes, Firenze," said the centaur beside him. "Do you recall its effect on the other heavenly bodies, when it is positioned like so?"

The centaur that had brought them there cleared his throat loudly. The other four centaurs turned.

"Aric," said a dun-colored centaur. "I see you were correct about the disturbance in the Forest."

"They are not men, but they will soon become so," said their centaur—Aric. "I believe they came to find us, although I doubt they will be truthful about their purpose. They bestowed a pile of foreign branches upon me—a useless gift. What think you, Junius?"

James noticed that Firenze was watching him and the others intently. If he had been human, James would have guessed he was about ten years old; he had not yet developed the sharp, serious look of his fellow centaurs. Experimentally, James gave him a small smile. Firenze gave him a small smile back.

"We will hear their story," said Junius, the dun-colored centaur. "Then we will decide what to do with them. Whether they can safely be returned to the castle, or if they must remain here, to be judged accordingly." He turned his attention to James, Sirius, and Peter, as if he had only just realized they understood English. "Explain yourselves. You must keep no secrets. Your kind are the most skilled liars of any creature upon this earth, and we will not stand for your deception."

James hadn't anticipated this. They'd hoped that the Alihotsy gift would be enough for an exchange without having to explain anything to the centaurs. But he gave the best explanation he could, with some enthusiastic interjections from Sirius (Peter stood silent, his arms swinging at his sides). James didn't mention Remus, because he didn't know what centaurs thought of werewolves, and he didn't mention the fact that no one knew what they were up to, because he didn't know what centaurs thought of rule-breaking. Therefore, the story came out sounding like the three of them had just decided to become Animagi on a whim, and were strangely desperate to complete the transformation as soon as possible.

"So we need this dew," he finished. "But neither sunlight nor human feet can have touched the place where it's collected for a week. And, well... this is the Forest…"

"And none of you have any feet," said Sirius helpfully.

"Or pants," said Peter, so quietly that only James heard.

"And we hoped… if we gave you something in return… you might… be able to help us?"

But this was clearly not something the centaurs wanted to hear. Aric made a noise that was half horse, half human, and all frightening. Junius pawed the ground, his eyes narrowed.

"We do not help humans," said a roan centaur. "This is something you ought to learn now rather than later. We owe you nothing. Your kind owes us hundreds of years of restitution."

"Does that mean you have the dew?" said Sirius, perking up slightly. "Because seriously, we'll give you whatever you want, no matter what it is—we'll give you loads of things, even. Way more than a tiny little bottle of dew is worth."

All of the centaurs except Firenze glared at Sirius. James couldn't stop himself putting a protective hand on his friend's shoulder.

"Our magic is not meant for the likes of you," said Junius. "There is nothing you could give us that could make up for the crimes your species have committed against ours."

"Well—that's why we want the dew!" said Sirius, and there was a familiar glimmer in his eyes now. "You see, we've been doing loads of reading about your—about your enormously noble and most unfairly oppressed species. And so we decided it isn't worth being wizards anymore, not with this terrible history we've got going for ourselves, and the truly unforgivable hardships we've inflicted upon you. So—so—we want to become Animagi in order to restitute to the best of our ability. We'll finish the potion, we'll become animals, and then there'll be a few less wizards in the world—everybody wins. And we'll, you know—humble ourselves, and all that. For the cause."

The centaurs glanced at Sirius again. They seemed less angry, but James couldn't tell what they were thinking.

"Yes," said Peter unexpectedly. "I—I'm hoping to become a flea. Very humble, fleas are."

"We'll all become fleas," said Sirius breathlessly. "I mean, you've met us; we'd make excellent fleas, wouldn't we? We're flea-people. Fleas of restitution."

"Tiny, humble, non-wizard fleas," agreed Peter.

For a half-second, James actually thought this Sirius Idea was going to work. But apparently centaurs were less gullible than Madam Hooch and Madam Pomfrey and Professor Flitwick and even Filch, because they all began to laugh uproariously. It was a frightening sound, like a group of choking horses.

"Perhaps you are not as close to being men as I suspected," said Aric. "Your lies are far less adroit than one would expect."

"Very entertaining, though," said a white centaur. "I will remember them with fondness."

"Indeed," said Junius, nodding. "As you have proven yourselves to be no more than foolish children, I will allow you to return to the castle unharmed. But you must never return to our Forest. To do so is to take responsibility for the breach of centaur law you have committed this night, and to willingly reap your reward."

The centaurs closed in on their group before any of them could utter a word of protest, forcing them back and back and back, until they were stumbling through the forest again, the lit turrets of the castle just visible from beyond the trees. Somehow the journey back seemed much quicker than the trip inside. James wondered if the centaurs' peculiar brand of magic had anything to do with it.

"What are we going to do?" hissed Sirius, as they neared Hagrid's hut. "We can't just give up, especially now that we know that they have it! This is for Remus—and we were so close!"

"Who's Remus?" said an interested voice from behind them.

James swung around. Firenze was standing behind them, his torso casually leaning against a tree. Peter yelped slightly. Sirius merely tensed, cursing softly under his breath.

"No one," said James quickly. "Look, we're leaving. We swear we are. We won't come back—we respect your people, we promise—"

"You don't," said Firenze matter-of-factly. "You always lie; that's what Papa says. But it's all right. You're humans; you can't help it. Anyway, I've been collecting dew at lessons. I've got far too much of it—wouldn't give you any otherwise, but it goes wrong if you keep it without using it. So, here. You can have it. As long as you don't tell anyone where you got it."

"No danger of that," said James slowly, his gaze moving to Firenze's hands, which were cupped around a small, corked bottle. "That's—that's really dew? I mean, the kind we need? It's really been away from sunlight and humans for seven days?"

"Are you insulting my intelligence?" said Firenze, frowning at James and holding the bottle closer to his chest. "Papa says humans always do that."

"No—no, of course not," said James quickly. "I only meant—actually, never mind; I didn't mean anything. But why are you helping us?"

"Because you're interesting," said Firenze simply. "And Papa always says the greatest strength of centaurs is found in thinking for ourselves."

"He's a wise man," said Sirius, stretching out a hand.

Firenze ignored him and slipped it into James', who nearly dropped it, startled. "I—well. Thank you," he said. "Thanks a lot."

Firenze merely smiled. "Have fun being fleas," he said, and cantered away.