They call Dumbledore because Remus has no idea what else to do. He fundamentally mistrusts the Ministry, has a werewolf's (reasonable) fear of being locked up and tested upon, and if Peter is sick or hurt, he is certain the Ministry or St. Mungo's will make it worse. If Peter is somehow stuck as a rat, Remus doesn't want to injure him trying to turn him back. Before they deal with any official people, Remus needs to understand what's going on, needs an ally and an advocate and Albus Dumbledore is far and away the most powerful person he has access to.
Remus leaves Harry with Molly. Harry is delighted by the surprise sleepover, though there is worry creasing his little face as Remus departs after his urgent message to Dumbledore is responded to with equal urgency. Harry can tell by his tone, Remus is sure, that something is wrong.
Remus clambers out of the grate in Dumbledore's office (a temporary connection with the Weasleys' having been established). He has Peter's limp little body clutched in his hands. Dumbledore is watching him from behind his desk, blue eyes alert and curious.
The sureallity of standing in Dumbledore's office - a place he's been only once, when he was ten, with his parents on a visit to meet the generous headmaster who let him come to school - makes him a little dizzy. All around him is gleaming wood, delicate gold and silver instruments, all lit up by the blaze of the sun setting outside the high windows.
"Remus," Dumbledore says with his usual quiet calm. "Have a seat. Water?"
Remus takes the chair in front of Dumbledore's desk. He leans forward, but instead of taking the proffered, levitating glass of water, he sets Peter down on the edge of the gleaming desk.
Dumbledore looks down at the rat with a frown, and then back up at Remus, his wand still aloft and suspending the water in midair. Remus takes the water; it seems rude not to.
"Your note," Dumbledore says slowly, "indicated you had something to share about the events of October 31st, 1981."
"Yes, sir."
"'Albus,' will do, Remus."
Remus nods terse, abstractly annoyed by Dumbledore, he's in no mood for this slow dance of manners. Something in his expression makes Dumbledore frown and look more closely at him. Remus takes a deep breath, makes himself relax his shoulders. He is doing the right thing by being here. He is keeping whatever this is away from Harry.
Apparently satisfied that Remus has composed himself, Dumbledore nods to the prone rat again.
"This rodent has something to do with this, I assume?"
"It's not a rat," Remus says tightly. Ah, is this why he feels so nauseous? He is about to admit to the man who fought to get him an education that he betrayed his trust and been lying to him for years.
Dumbledore is looking more closely at the rat, peering at the little form but not touching it. He reaches out one long fingered hand, lets it hover over the rat as he mumbles some quiet spellwork to himself. Nothing visibly happens, but Dumbledore blinks suddenly and looks back to Remus, his gaze piercing. Remus feels like a wayward child, not like someone raising a child.
"Peter Pettigrew," Dumbledore supplies evenly. "Ah. Fair to say I am missing some information."
Remus forces it out quickly, the words feel like rocks in his throat. "He was an animagus. He - James and him and - They were just trying to help me, sir," he says. "They did it in school, be-because if they were animals they could - But forgive me, sir, that doesn't matter right now," he says more forcefully, sitting up straighter in his chair. "He died. Peter died. Dozens of witnesses saw it. I don't - I don't understand how he's… here."
"You appear to understand somewhat more than I do," Dumbledore says. "We are in no rush, Remus. We have time to talk. Harry is, I'm sure, well looked after for the evening?" Remus nods. "You have very clearly had a shock. I see water is not quite doing the trick - here."
A cup of tea materializes on a little table beside Remus' chair. It is a simple breakfast tea, brewed strong and served black in a simple white tea cup, as Remus prefers. The smell is immediately soothing. Offering it in this moment is exactly what Remus would have done himself, were the roles reversed, so he takes it, holds it, feels a little grounded by the almost uncomfortable warmth of the porcelain. Staring into it gives his eyes somewhere to rest other than Dumbledore's spectacles. He begins again.
"They became animagi to help me through transformations," he says quietly. "They managed it in fifth year. I-I tried to dissuade them, but honestly I never thought they'd manage it. I thought… I thought about telling you, back in - when it was obvious there was a spy, but I thought - I was afraid of getting James and Peter arrested. His-his form wouldn't have leant itself to spying, anyway…"
This all sounds very weak to Remus, but when he looks up, Dumbledore's expression is one of attentive curiosity rather than anger.
"What were their forms?" he asks.
"James was a stag," Remus says. "Peter, obvious, a rat." Remus talks about James and Lily often with Harry, he can get through their names fairly easily now. Peter trips him up but that last one he can barely stand to think. "And a dog. Massive. Anyone would have noticed if he was lurking around that way."
Dumbledore nods. "There is more to discuss there, Remus, but I think it's time we turn to the matter at hand. How came Mr. Pettigrew to the Burrow?"
"I have no idea. I only saw him just now. I think - I think Charlie Weasley picked him up in a Diagon Alley gift shop. Molly mentioned he's getting ready for school."
Another slow nod. Dumbledore was now looking down at the rat.
"To ensure you and I are on the same page before we proceed," Dumbledore says. "The last we knew of Peter, he had learned of the tragedy at the Potters, tracked down Black to seek revenge and was killed for his efforts, along with many innocent muggles. You yourself were away in the North at the time, observing a pack on my orders."
Numb, Remus nods again.
"Peter died," he says. "I mean - I-we all thought he did. Why would he… I understand he might have hidden away or something, but why stay like that so long?"
"Let's ask him."
Remus is not at all prepared for the quick jab of Dumbledore's wand. The rat is sent to the floor and then there are several more quick spells cast, and the little body is twisting, changing, a head and arms sprouting grotesquely, and Remus stands involuntarily, stumbling backwards and away until he hits the bookshelves by the windows. He feels his mouth fall open and gapes at what is, unmistakably, the prone figure of Peter Pettigrew. The sunlight through the windows cast a rosy glow over his unconscious features.
Remus' stuttering heart leaps. Peter. Wormy. His friend. If he is honest, his oldest friend, the first person outside his family that he ever truly trusted. Who he knew could keep a secret, who never drew attention, who sat in quiet companionship with him through that first year, just another lonely boy unsure of his place at Hogwarts. He looks so scruffy now, clothes a nondescript grey not unlike his fur coat, his blonde hair unkempt. Remus starts toward him, wanting to help him up, but Dumbledore holds out a hand and he stops. Dumbledore's next wand wave revives the other man.
Peter's eyes fly open and he sits up with a gasp. He takes in the sight of Dumbledore with a wand on him, gasps again and immediately scrambles backward. He twists, about to transform, and then cries out in pain, coming up short from some binding spell Dumbledore must have cast to prevent that escape route.
None of this makes sense to Remus, his mind refuses to cooperate, he just sees a friend in pain. He starts forward.
"Peter-"
The look Peter gives him is of utter terror. He looks at Remus as though he's seeing the wolf instead, as though he's afraid of being torn apart.
"Peter," he tries again, forcing his voice even, concerned that Peter has been tortured or forced to be a rat, though he can't imagine why. "It's okay."
"Peter Pettigrew," Dumbledore says, his voice far colder than Remus expected. "Get up."
Peter cowers deeper against the shelves. Remus looks at Dumbledore in slight reproach. He finds that Dumbledore is staring at Peter with an icy fury that Remus has never seen before.
"Dumbledore?" he says uncertainly.
The old man's eyes stay fixed on Peter, who is staring back at him with mute horror. "Remus," Dumbledore says, "I am afraid we are about to learn something terrible. I perhaps should have offered something stronger than that tea."
Remus stares at him.
"You may be thinking," Dumbledore continues, "that Peter's mind was affected by some spell, that he was tortured into madness, or trapped in his rat form?" he guesses with eerie accuracy. "I cast some fairly simple diagnostics, and that is not the case. There are other traces of powerful magic around you though, Peter, did you know?"
Peter whimpers and looks at the floor.
"If you'd cast magic yourself in the intervening years," says Dumbledore. "It might have faded, but clearly you haven't. It isn't hard to see, if you know how to look. Which I do."
"No," Peter groans. "No, I didn't-I didn't…"
"Peter?" Remus says weakly.
Peter looks at him again, eyes suddenly bright and pleading. "Remus! Moony - you can't trust him! He's-"
"Silence," Dumbledore orders.
Remus feels sick. The desperate fear in Peter's face is utterly at odds with the thought of his innocence. Remus' awareness seems to detach from himself. He feels like he's watching the scene playing out from above.
"There are traces on you," Dumbledore says, "of a blasting curse. Which-"
"Black blasted the whole street!" Peter protests. "I had to hide, I knew he'd come after-"
"I assure you, Peter," Dumbledore says loudly. "That it is quite useless to lie to me."
"I didn't do it! I'd never-"
"I will give it to you that those traces could cling to you from your proximity to the spell caster," Dumbledore interrupts. "But there is no innocent explanation for the traces of Lily's Secret Keeper charm on you."
Remus' awareness slams back into his body. HIs face feels hot.
"What? Y-you? You were-?"
"Remus, no! I didn't - please -"
"You were the secret keeper?"
"I- but Sirius - You know Sirius was always unstable, his temper, he-"
Remus' vision is narrowing in on Peter's face and blackens when he says that name. His mind is flying back to memories he hasn't touched in years, that suddenly come back in vibrant color. He rewrites that last year - that last, terrible year. It falls out of the shape it's been forced into and suddenly he sees something new.
"You kept saying that," he says blankly. "You kept saying that about him, then. Every time I doubted him, you agreed, you encouraged it…"
"Cause you were right!" Peter shouts, but Remus can hear the desperation in it, can smell Peter's panic and hear his pulse racing. He presses.
"Why didn't we see-? You were always hiding behind us," Remus says. He wants to throw up. "We were always your shields…"
"And he thought he wasn't safe anymore," Dumbledore supplies, voice turning uncharacteristically with disgust. "He wanted somewhere new to hide."
"Lily and James," Remus gasps, their names painful again. "Lily and James… Harry."
"No, I didn't," Peter groans. "I never…"
Remus wants to run. He wants to get back to Harry and hug him and never let go.
"Confess," Dumbledore says sternly. "You turned on the Potters. You'd been spying for the Death Eaters for over a year."
Peter is sobbing.
Remus' mind finishes assembling the picture. Slots the last pieces together. He throws out the hope he had for Peter's innocence. He throws it away because of who he can save in Peter's place.
"Sirius."
Peter's face blanches utterly white.
"Sirius," Remus gasps again. "You let him take the fall - you let him rot in there - you-"
"I didn't - I didn't mean to -"
Remus launches himself across the room, throwing himself at Peter. He comes up against Dumbledore's shielding spell and falls backward. Peter begs forgiveness as Remus collapses to the floor, unsure if the ragged sounds escaping him are tears or laughter.