Even afterwards it was difficult for Snape to reconstruct what had happened in those few brief seconds before the room was engulfed in deadly green light.

He saw Fudge pull out his wand. Both Dumbledore and McGonagall had lowered their wands. What were they thinking? He shouted out something, a warning, even as he pushed his way through the Wizengamot members, who were too busy gaping at the scene in front of them to do anything constructive. But the fools wouldn't get out of his way, and he knew, sickeningly, that he would be too late even as he heard Fudge's voice, high with glee, screaming the curse that would kill the man to whom Snape owed everything.

Minerva saw, and threw herself in front of Dumbledore.

Madam Bones raised her wand.

A silver hand suddenly grasped Fudge's wrist even as he spoke the last word.

With a surprising strength, Dumbledore pushed Minerva away from him.

On the last syllable, the silver hand snapped Fudge's hand so that his wand was pointing at himself. In the eerie silence Snape could hear the bones loudly break. Fudge's eyes were suddenly wide with terror and pain – but it was too late.

Then the green light, so familiar and still so frightening, shot through the attic in deadly answer to the worst of curses.

Or so, at that moment, Snape thought it. Later, he revised his opinion.

There are, after all, worse things than death.

But at that moment, after the light had disappeared and he finally made it to where Dumbledore was standing, the worst curse he knew was the Avada Kedavra, and he was filled with relief that the Headmaster- his only friend – had not been its victim. Instead, the body on the floor was that of Cornelius Fudge. And still holding onto the wrist of the dead man was the silver hand, bequeathed to him by Voldemort on the night of his rebirth, of Peter Pettigrew.

Lucius' words flashed through Snape's mind. "Ironic, that the rat and the traitor outlived us all." Lucius would have been amused by this.

Madam Bones lowered her wand slightly. "Hellfire," she breathed.

Professor McGonagall moved back to Dumbledore's side, but he seemed not to see her. His attention was instead fixed upon Cornelius Fudge, and on his face was an expression of deep sadness. Minerva's own wand was out again, and now it was pointing straight at Pettigrew.

Snape coughed politely. "Pettigrew," he said suavely. "Perhaps you wouldn't mind letting go of the Minister's arm? I don't think he's in any position to harm anyone anymore, and it seems to make Professor McGonagall here rather edgy to see you so close to a wand."

Pettigrew dropped the arm like it was suddenly on fire.

"Smooth, Severus," murmured Amelia Bones.

He inclined his head towards her in thanks.

Pettigrew's bright eyes darted around the group, as he let out a high-pitched nervous giggle. He finally fixed his gaze on Dumbledore. "I saved you, yes? He was trying to kill you, but I saved you."

Dumbledore said nothing.

"He threatened to torture me if I didn't do what he wanted. So did Voldemort! I've always been threatened… always…" There was immense self-pity in his tone. It set Severus' teeth on edge.

By the look on Minerva McGonagall's face, it had a similar effect on her.

"But you," the voice brightened, took on a whining hope, "I saved you! And you wouldn't threaten me, or hurt me, Headmaster. You're the greatest wizard in the world – you have no need to threaten me, or hurt me – what harm could I, weak as I am, ever do to you?" Pettigrew took a small step closer to Dumbledore, his hands outstretched, pleading. McGonagall let out a hissing breath, and Pettigrew stopped dead in his tracks, glancing over at her nervously.

Then he turned back to Dumbledore, who was watching him impassively. "You wouldn't – you won't kill me, will you, Professor?"

Dumbledore shook his head slowly. "No, I will not kill you, Peter. But I do not know what is to be done with you."

Snape felt that he could have offered some useful suggestions, had he been asked.

Dumbledore continued heavily, "You are far more dangerous than you would have me believe."

"Me? No, Professor! I've no real power – I've just been an errand boy, used by evil wizards… Let me give my loyalty to you, Professor Dumbledore, let me serve you, and I promise you I'll never –"

"Promise?" Snape could not help but sneer at that. "You promise, Pettigrew? Ask the Potters what your promises are worth."

"I was forced!" Pettigrew cried. "Voldemort threatened to –"

"Oh, shut up, Pettigrew!" Madam Bones had obviously had enough. She turned to Dumbledore. "Well, if we aren't going to kill him – and I don't see how we can now, since he did save your life – then what are we to do with him? We can't keep him forever locked up in Azkaban now the Dementors are gone, but he's the last Death Eater alive. We can't let him go!"

Dumbledore sighed. "I do not know," he admitted.

"I do."

Minerva McGonagall spoke with a strangely gentle calm, and moved a little away from Dumbledore. Her wand was still pointed directly at Pettigrew, and he turned to watch her warily.

"You offend me, Wormtail," she continued. "Your existence is an offence, because you are the very worst of the Death Eaters. Those who died downstairs at least held a belief; a wrong and an evil belief, but one they had the courage to sacrifice themselves for. You have no belief in anything save your own survival, and you would sacrifice and betray anyone and anything to keep yourself safe. Your Animagus form was very well chosen, Rat; let that be your punishment."

He looked puzzled. Snape couldn't work out what she meant either. But as her power suddenly billowed her robes around her, he knew – and so did everyone else in the room – that something of a very high order of magic was about to happen in the dusty attic. For Minerva McGonagall was a very powerful witch.

"Animagi es" From the first syllable of the spell blue-white sparks began to crawl along her wand.

"Alienus forma capiebas."

"Minerva, no!" An anguished cry from Dumbledore. But she ignored him.

"Animagi sum idem

Et mihi potestas teum do." The blue-white sparks erupted from her wand towards her. Her face contorted with pain as they swirled around her.

Snape felt the hair on the back of his neck stand up. The huge power of this spell was palpable in the room.

"Animagi te damno!" A ringing sound hurt Snape's ears. Pettigrew tried to shrink away, but his feet seemed fixed to the floor, and he fell instead.

"Nunquam postea mutaties

Semper bestiola eris."

The words seemed almost forced out of her now. She fell to her knees as blue fire erupted from her wand, but kept it pointed steadily at the terrified Pettigrew.

"Per sacrificium mihi

Sino fieri!"

And with that last cry cold fire, wizard fire, the oldest of magics, erupted from her body and she collapsed onto the floor. But her wand hand she forced up, and waved it once more at Pettigrew. And the flames traveled from her now unconscious form to him.

He screamed as the flames enveloped him, and he writhed in them as he slowly changed.

Dwindled.

His clothes fell on the floor, untouched by the fire, which grew smaller and smaller. Until, at last, a small nose appeared, twitching.

A rat. Balding, grubby, old. With a silver paw.

With a loud squeak it skittered along the floorboards, and Snape went to chase it.

"Leave it!" Dumbledore had already moved to Minerva's unmoving form. He gathered her carefully in his arms and stood.

"What?" Snape was dumbfounded. "Let him get away? He'll change back and we'll have all this to do again!"

"No," Dumbledore said quietly as he shifted Minerva to rest her head more comfortably on his shoulder. "It is a permanent Transfiguration, Severus. He will be forever a rat."

"That's not possible!" one of the Wizengamot protested loudly.

"It is," Dumbledore corrected him. "It is simply that it has never been done."

"Why?" asked the same voice.

"Because," Dumbledore gazed sadly at the woman cradled in his arms. "Permanent Transfiguration requires a sacrifice."