8. The first transformation is usually uncomfortable and frightening. Clothing and items such as glasses or jewellery meld to the skin and become one with fur, scales or spikes. Do not resist and do not panic or the animal mind may gain the ascendancy and you could do something foolish, such as try to escape through a window or charge a wall.

• • •

The pain was fading, but nothing else was. If anything, the second heartbeat—the stag's heartbeat, he remembered—was growing even stronger. James, as he recognized himself, was rapidly dissolving.

He couldn't stop himself from crying out (more from surprise than from pain, now) when his glasses suddenly slammed into the space around his eyes and sank beneath his skin. His robes, too, were shrinking, sticking to him, pulling themselves too far inward.

Is this how it is for Remus? wondered a small voice inside his head, then shook off the thought completely, furious with himself.

No. This was definitely not how it was for Remus.

And now it was his body that was changing, although the pain was gone, and he only felt a little cramped, and yet also a little too stretched out. His back arced upward, while his arms and legs shot downward, and that jumper-soft fur sprouted from his neck to his spine to the tail that had suddenly appeared behind him. He didn't have fingers anymore, nor toes; they had hardened into hooves, and what had started as a light weight on his head was gradually growing heavier as his antlers grew and branched out, mirror images of each other.

And then it stopped. It all stopped.

If he could have, James would have grinned. As it was, he probably looked pretty stupid: a fully-grown stag, standing in the middle of a narrow room with glass walls, his mouth hanging open, his heartbeat soft again now, but beating twice its usual rhythm.

This was not how it was for Remus, but it would never again be as bad for him as it had been before. Not now. Not now that James could do this.

• • •

9. When your transformation is complete you should find yourself physically comfortable. You are strongly advised to pick up your wand at once, and hide it in a place of safekeeping, where you will be able to find it when you regain a human form.

• • •

James didn't bother moving his wand; it was perfectly safe where it was, lying on the floor, needed by nobody. Instead, he looked, for the first time, left and right, hoping to find out what had happened to Sirius and Peter.

Sirius was easy, because he turned to look at James at exactly the same time James turned to him. Inside his head, James laughed aloud. Of course that's what Sirius would be. Of course.

Oh, he was going to come up with so many horrible dog-themed jokes in the weeks to come.

The huge black mongrel on the other side of the wall wagged its tail enthusiastically. A calm presence from somewhere within James told him that stags did nothing of the sort, even in response, so he merely glanced back at Sirius. Then he put on his stupid grin again, because even if stags didn't smile, Jameses did, and Sirius grinned back, looking for all the world like a stray who had just happened upon a steak.

Peter, James thought then, and he was pretty sure Sirius was thinking the same thing.

Their heads turned together, looking beyond the wall on James' left into the room where they had last seen their friend. But there was no one—and indeed, no creature—inside. At least to James' eyes (suddenly color-blind, blurred due to the non-invention of stag glasses), the room was completely empty.

James and Sirius exchanged glances. Without so much as some makeshift sign language, they proceeded to their respective gates, managed to get them open (James with more difficulty, as hooves are clumsier than paws), and fumbled into Peter's enclosure, tripping over themselves, not yet used to the way their new bodies moved—but that didn't matter now.

It should be impossible for Peter to be missing. The Room of Requirement had been specifically set up to make that impossible—there were no windows, no doors, nothing that could break; James had made sure to ask for that as they had created this version of the room. So what had happened?

He could have run, said a traitorous voice in James' head. He could have watched you and Sirius drink the potion, seen how it hurt, opened the gate, got the hell out—

–but he wouldn't have, James told himself. Peter was one of them; had been since the second week of first year. He was loyal to a fault. He had gone this far with them, hadn't he, even though it was clear he was afraid? He was Peter. He'd tried jinx Avery once in James' defense, despite knowing he had no chance. He'd once volunteered to send every member of Sirius' family a Howler. He played wizard's chess with Remus every month while he was recovering, pretending he didn't care that he always lost. And he'd gone into the Forest with them, had faced real danger with them—had even spoken to the centaurs—

Sirius barked, a sound James hadn't expected, and one that still seemed bizarre coming from his best friend, dog though he might be. James turned, and suddenly all the cold inside him warmed again.

Peter wasn't missing at all. He had only shrunk.

The rat at James' hooves chittered excitably, its long, wormlike tail whipping back and forth across the floor. James, hoping this was Peter's choice rather than the rat's, tried to reassure him, a decision that resulted in an unexpected snorting noise from the stag's nose. Sirius barked again, in such a way that James knew he was laughing at him.

He drew himself up, hoping to look at least slightly dignified, like the stag in his dream, but instead he found himself splayed onto the floor like a newborn foal. He had never imagined that being a stag would take practice, but there you were. At least he wasn't going to have to learn to fetch.

Beside him, Sirius was shifting, his dog's body growing tall and lean, the dark fur withdrawing into his skin. James remembered what the Animagus book said, that the only thing you needed to do to change back was to remember who you were.

Who he was really wanted to burst out of the Room of Requirement and run straight to Remus. James found he had no difficulty with changing back at all.