Peter Pettigrew was feeling depressed. It was January, the full moon was only a few weeks away, and he was the only one of his friends who was not yet a proper Animagus.

It hadn't surprised him that Sirius and James had pulled it off first. They were brilliant in a way that Peter knew he was not. There was no point being precious about it: Peter knew he wasn't as talented as his friends. It wasn't like anyone ever let him forget it. So he had expected they would get it first and welcomed all the help they'd given him throughout the process. But enough was enough. There was nothing else they could do to help him now. It was all on him.

Go on, he goaded himself. Prove you're good enough to be a Marauder.

It was Wednesday morning of the first week back from the Christmas holidays and, judging by the snores that filled the quiet dormitory, his friends were still asleep. James might be up — he was stupid about mornings, always getting up early and running off to do things. Peter generally slept as late as possible, but in an entirely uncharacteristic bout of insomnia, he'd risen with the birds. So instead he sat cross-legged on his bed, eyes shut, trying to bend his mind into something else.

Something it very much did not want to bend into.

Peter thought meditation was rubbish. It was very hard to not think about anything, especially as Peter had lots of things to think about. He had a few reservations about this whole 'become Animagi and cavort with a werewolf' plan. For one thing, it was illegal. And for another, he wasn't convinced James and Sirius had really thought it all through.

Peter was always a little scared of Remus when he saw him after the full moon. Last month the boy had returned with a deep gouge along the side of his face, carved right up to his brow. Peter had once sliced his hand with a knife while dicing a salamander tail for Potions, and Madam Pomfrey had healed it in seconds. He'd asked James why she couldn't do the same for Remus.

"Cursed wounds, aren't they?" James had said knowledgeably. "Werewolf scratches don't heal properly."

It wasn't Remus's fault, Peter understood that, but it still frightened him to think that his friend had done all of that to himself — that he became something that did that. What might he do to Peter?

But these troubles paled in comparison to his One Big Fear: transforming into an Animagus. What if he did it wrong? What if he got stuck in the form of an animal, or half-way between, or lost his mind entirely? He'd read the books. He'd seen the catastrophes.

Or maybe worse still: What if he actually pulled it off but became something utterly useless like a bug or — oh Merlin — a whale? What if he was just sitting in the dormitory one night, trying to meditate and do the stupid non-verbal-wandless-magic thingy, and all of a sudden he turned into a giant whale, all blubber and fins spilling out the doors and down the stairs? They'd have to magic him out of the tower. He'd have to go live in the lake with the giant squid. Oh, there goes poor Peter the whale, they'd say, toss him your toast, what a pathetic —

Oh, right. Nothing. He was supposed to be thinking about nothing.

He wriggled his nose in discomfort and tried to focus on Remus's snoring instead. Remus was terrible about snoring, but the worst part was he didn't believe any of them when they told him about it. He'd sit there, very tall and dignified and insist it must've been Sirius. Sirius did snore, but nothing like Remus's great grumbles.

Somewhere in the distance, an owl hooted. Peter started in fright then scurried under the covers, burrowing away from the — wait, what?

His eyes darted here and there; the world beneath his sheets suddenly seemed much larger, and he much, much smaller. He craned his neck to get a glimpse of himself. Little paws, long tail…oh sweet Merlin, he'd done it.

His heart was beating impossibly fast, his mind racing, and he was suddenly very aware of thin, delicate whiskers that threaded along his cheeks. He sniffed.

Okay, okay…he still had his mind. He was still Peter. That part had gone all right. And he wasn't a whale! He was…a rat.

Huh.

Before he could ruminate on this with his chirping, spinning mind, he heard Sirius's voice call from behind the bed hangings: "What the hell is Peter doing? He's going to make us miss breakfast."

"Wake him up, then," came James's careless reply.

Peter supposed he must have spaced out while meditating…he wondered what time it was, but he could hardly check his watch like this, so he concentrated all his energy on his human form, just like the books had said, and…and…nothing happened.

"Oi, Peter!" Sirius called. "Get up, you great sloth."

Peter tried again to transform back. And again, and again, and again…

Oh no. Oh no, no, no, no, no…

It was his worst nightmare realized. He couldn't do it. He was stuck — he was stuck as a rat.

Just then, Sirius threw open the bed hangings. He loomed larger than life before Peter's small, beady rat-eyes. "Wha — he's not here," said Sirius, frowning.

"What do you mean he's not here? He never left."

"I mean, he's not here. Look, the bed's empt—arrgh! Why's there a rat under his pillow?"

Peter squeaked desperately.

"A rat?" said James, and then he too appeared, squinting down at him.

"Are you all coming or what?" Remus's voice floated from the stairwell.

"You don't think…" said James slowly, leaning forward to investigate Peter the rat.

"Hang on, Remus!" called Sirius. "Pete's pulled a vanishing act."

"What?" Remus came hurrying into view. "What do you mean he's — why is there a rat —?"

"Exactly," said James with a knowing nod. "Peter?" he asked tentatively. "Is that you?"

Yes! Yes, it's me, I'm stuck, help, help, help! Peter tried to say, but of course all that came out was frantic squeaking.

"He did it!" cried James with a triumphant clap as Sirius roared with laughter. "He did it, he did it!"

"Oh my god," said Remus faintly.

Suddenly, Peter felt a lurch in his stomach as Sirius picked him up by the tail and examined him. "Are we sure this is him and not just some very chatty rodent who got into our sweets?"

"Peter," said James, "if that's you, er…squeak three times."

Peter obliged, swinging wretchedly before their swimming faces.

"Definitely him."

"Put him down, Sirius," said Remus. Peter fell with a plop back to the bed.

"A rat," said Sirius, and he sounded somewhere between amused and disdainful. "Not sure how that will help with a werewolf, but all right, we'll celebrate later. Come on, Peter, transform back. We've got to get going."

Peter squeaked miserably.

"Come on. We haven't got all day. Change back."

Squeak, squeak, squeak squeak, squeak. Maybe he could learn Morse code. They read about that in that in Muggle Studies last year, how Muggles use tapping to convey messages…maybe he'd just have to squeak his way through the rest of his life.

Remus understood first. His eyes widened with alarm. "I don't think he can."

"What?"

"I don't think he can change back. Oh god, he's stuck."

"He can't be," said James. "Changing back is the easy part. Pete, if you're stuck, squeak three more times."

Squeak, squeak, squeak.

"Shit," said Sirius.

"Oh, this is bad," fretted Remus. "Really, really bad."

"We'll figure it out," said James. "Don't worry, Pete, we'll get you back to normal."

"How? You can't exactly go to Professor McGonagall and say, 'Sorry, our illegal Animagus experiment went south, and now our friend's a rat, can you fix it please?'"

"Relax, Remus. I remember reading about a spell you could use to force someone out of their Animagus form. We'll go to the library after class, find it, and everything will be sorted by tonight."

"Well, Pete, looks like you get to skip Charms anyway," said Sirius lightly.

"Yeah, and stay in the dormitory, all right? Bertha Jorkins has a cat, remember."

And then they left him.

Bloody typical, was his first, resentful thought. Of course he'd be the one to screw it up. Of course he'd be something small and tiny and useless like a rat. Animagi were supposed to be reflections of your soul, right? Well, who was more tiny and useless than Peter Pettigrew? He'd been kidding himself with this whole thing. Most grown wizards can't even become Animagi, so what in the name of Merlin had made him think he was good enough to do this?

Peter burrowed into his blankets miserably. There was nothing to do but wait.

A few hours later (or days or months or years…Peter couldn't be sure), James returned. "All right, Pete?" he asked the rat. Peter gave him a doleful squeak.

James knelt down by the bed and grinned. "No need to be quite so morose. If we can't un-rat you, I promise I'll get you a really grand running wheel and bring you cheese every day. Oh, speaking of which, I brought you a sandwich." He fished a slightly-squashed ham and cheese sandwich out of his pocket and presented it to Peter, who nibbled at it gratefully. He'd missed breakfast and he was starving.

"There are worse ways to live your life than as a rat, eh?" said James with an amused smirk. Peter scowled at him, or whatever the rat equivalent of scowling was. James laughed. "I'm joking. We'll work it out. Want to come to the library with us? Sirius and Remus are already on their way there now. Come on, you can kip in my pocket. A change of scenery will do you good."

And he scooped Peter up in his hands and tucked him in his front pocket along with the remaining bit of sandwich. Nestled among the pocket-lint and crumbs, Peter took a moment to appreciate what an entirely strange day he was having. Still, he was pleased James had come back for him. He had been beginning to feel a bit forlorn, and while bumbling along in James's pocket was perhaps not how he'd planned on spending his Wednesday afternoon, at least his friend had remembered him.

It had often occurred to Peter that it was sheer luck he'd ended up with friends like James, Sirius, and Remus. It was purely an accident of fate that landed him in what he considered the coolest, most exclusive gang at Hogwarts. If he'd been in any other house, or perhaps a year younger, Peter was quite sure that neither Sirius nor James would have ever given him the time of day.

Then again, they almost hadn't anyway. Remus had been the one who'd always included him back in first year. Peter knew the other boys had let him tag along mostly to humor Remus. It wasn't until they'd discovered Remus was a werewolf that the four boys truly became a unified group, bound together by the invisible knot of an unspeakable secret.

"Oh, hello," said Remus's voice. They must've arrived at the library. Peter couldn't really tell, it was all dark in the pocket. "What took you so long?"

"I went to go get Pete," explained James.

"You what?"

James gently tapped his pocket.

"You brought him?"

"Why not?" James shrugged and Peter shifted in the pocket with the rise of his shoulders. "It'd be boring stuck in that room all day."

"Well, keep him in there because Madam Pince would kick us out if she thought we were bringing rats near her precious books."

"Right-o," said James. Then he peered into his pocket, and Peter's vision was filled with the glimpse of a large pair of glasses glinting at him. "You all right in there?"

Peter squeaked his approval; James laughed and went to work.

Eventually, the sandwich finished, Peter fell into a drowsy half-sleep, tucked away in the snug of James's pocket, the soft rustling of book pages and the sound of James's breathing the only noise in the quiet library. Then, Sirius's voice pierced through his slumber.

"I think I've got it."

"Let me see," said James, and Peter tumbled a bit as James leaned forward to peer at Sirius's book. "Oh, that looks complicated. Nonverbal…all right, well, copy that down. We'll go back up to the dormitory. We obviously can't do it here."

The scrape of chairs echoed as his friends stood to depart. Nestled in James's pocket, Peter fell into the rhythm of footsteps and did what he had done for the whole day: He waited.

"Are you sure he can breathe in there?" came Remus's voice from outside the pocket.

"He's breathing!" said James, a tad defensively. "You want out, Pete?"

Peter wondered why they kept asking him questions he clearly couldn't answer. Before he could formulate a proper squeak in response, James's hand was lifting him out of the pocket. The faces of Sirius, Remus and James all loomed above him. They were in a deserted corridor on the fifth floor, one of the many shortcuts they had developed over the years.

"Here," said James. "He can perch on my shoulder. Get some fresh air. That better?"

"That's stupid," said Sirius. "What are people going to think if you walk around with a rat on your shoulder?"

"We'll just tell everyone he got a new pet," suggested Remus. "Lots of people have pet rats."

"There you go, Pete," drawled Sirius. "If we can't get you back to normal, you can just live as James's new pet. So don't worry at all."

"I've already told him I'd get him a running wheel," said James happily. "This is turning out to be a good month for me. I got a new dog and a pet rat. I bet old Beatrice is feeling awfully foolish right now."

"Who?"

"My sixth governess. She's the one who told my parents I wasn't fit to care for a living creature. But this was just after the Niffler incident, you see."

"I take it back," sniggered Sirius. "Maybe you should worry, Pete."

Yeah, yeah, laugh it up, thought Peter bitterly. You're not the one stuck as a bloody rat.

"You had six governesses?" asked Remus incredulously.

"No, I had nine."

"Nine? Why?"

"Well, the first eight all quit."

Remus and Sirius howled with laughter.

"The ninth did as well, actually, but she was the last. I put a toad in her porridge, and for some reason that upset her. After her, mum and dad left most of it up to Pixie, poor old thing, but — ow, Pete, what are you doing?"

Peter had just dug his nails into James's shoulder. Instinct had overtaken him, and he was frozen in fear. A moment later, skirting around the stone wall, appeared the scrawny form of Mrs. Norris, Filch's awful cat.

"Ah," said James.

"Shoo!" said Remus.

Mrs. Norris hissed, her large eyes locked on Peter.

"Go on, get out of here," said Sirius, giving a little kick towards the cat. In a flash of mangy fur, the cat lurched forward and instinct overwhelmed him. Peter scrambled from James's shoulder, twisting in the air as he fell, landing on the hard, stone floor. Then he took off, bolting across the corridor, Mrs. Norris at his heels.

Behind him he could hear the heavy tread of his friends' feet as they raced after cat and rat.

"Stop!" hollered Remus. "Peter!"

But Mrs. Norris was still close behind him, and Peter kept running, a scramble of rat-feet, a swish of a long, bald tail. Down a spiraling stone staircase and under the fraying edges of a tapestry, through a hall of dark wood and rusty armor…until at last he saw a small hole in the wainscoting and, scrabbling across the floor, he slid into it.

He scooted away from the exit into the darkness, whiskers quivering. A dusty paw swiped the air before him; Mrs. Norris was out there, waiting…

"What is it, my sweet?" came the reedy voice of Mr. Filch, who never seemed to be far from his feline companion. "Chasing rats again? The castle's teeming with them…verminous plague-ridden scum…"

Mrs. Norris took another fruitless swipe through the hole, then, with a huff, Peter registered the resentful pad of paws plodding down the hall after Filch.

His stuttering heart was ricocheting around his tiny ribcage. He blinked his beady rat-eyes and looked around the darkness that had swallowed him. He was inside the castle walls…literally. As his vision adjusted, a labyrinth of twisting, turning pipes appeared before him. On the dusty floor were piles of wood shavings and the sooty scrabble of previous rodent denizens.

He glanced at the little hole through which he had entered the wall, pale light spilling through its gap. The safest thing to do would be to slip back out, scurry along up to Gryffindor tower, find his friends, and let them fix him…but then, what if Mrs. Norris was lingering nearby? At least in the walls, no cats could get him.

His friends would be worrying, though.

Good, said a nasty little voice in his head. Let them worry. Be a new experience for them, won't it? Let them think poor, incompetent Peter is lost forever…

With this hard little stone of a thought, Peter leapt up onto the closest pipe. The burnished brass glinted in the single smudge of light from the hole in the wall, but the dark wasn't bothering him nearly so much now. The only problem was that he had no idea where he was going, on account of how he had no idea where he was. He needed a landmark, he thought as he scurried along the pipes.

Then, a familiar Scottish brogue echoed through the walls.

"I understand you're upset, Caradoc," came the voice of Professor McGonagall, "but the school governors—"

"Sod the governors," replied an angry voice that, after a moment, Peter realized belonged to his Defense Against the Dark Arts professor. "Dumbledore hired me to teach them defense, I'm teaching them defense. If that's too much for their delicate sensibilities…"

"They're third years. They don't need to hear about Death Eater atrocities."

"They'll hear about them one way or another — whether I tell them or not!"

McGonagall sighed. "I understand your position, but we're a school, not an army. Regardless of what the Headmaster wishes, the governors cannot be ignored. A student complained, Caradoc."

"And let me guess, his father is a very important pure-blood governor and donor to the school?"

"If you continue in this vein, they'll have you removed. Dumbledore is not as all-powerful as you imagine."

"I don't imagine much, considering he's hardly ever here."

"And it would certainly be no help to your students, if you were ousted," finished McGonagall, stubbornly ignoring his interruptions. Then, another sigh. "Stick to the curriculum. There's time for all the other horrors in the N.E.W.T. levels."

"Let's hope there is."

Peter filed this conversation away as 'curious', and focused instead on the realization that he must be by the staffroom. Which meant to get to Gryffindor Tower, he needed to go up.

The tangle of pipes climbed ever upwards in the looping, snarling incompetence of centuries of Wizarding plumbing. Peter clambered upwards, upwards…through shaft and beam, floorboards and rotting wood. When he thought perhaps he'd gone high enough, he skittered off a copper pipe and down a stretch of wall. Surely another rat had burrowed out a hole somewhere on this floor…

Finally he found a split in the baseboard and, peeking his twitching nose carefully out first, he sensed it was safe to exit. He scuttered out and looked around.

He was not where he'd thought he would be. In fact, he had no idea where he was. He'd never seen any room like this. It was large and circular with a vaulted, starry ceiling, tall arched windows and walls draped in blue and bronze.

Hang on — blue and bronze?

Merlin…he was in the Ravenclaw common room! That had to be it. How could he…? But it was. It was definitely the Ravenclaw common room! And…oh shit, it was full of students.

He scampered back under the baseboard, eager to avoid the squeal or stomp of a squeamish first year ill-adapted to the castle's non-human inhabitants. Besides, he was hungry. It was time to get back to his own common room.

If he could ever find it.

Still, there was a note of triumph in his pattering step as he sped along the labyrinthine pipes. He had just waltzed right in, no password, nothing. This was amazing. He could go anywhere. He could go places no one else in the castle could go!

Maybe…maybe being a rat wasn't going to be quite as useless as he'd thought.