"Potter."
Harry turned. Snape was standing at the edge of the walkway, his robes moving in the wind coming off the lake, his face doing the thing it sometimes did when Harry looked closely enough — which was carry something it never put into words and probably never would.
"Come with me."
Harry looked at Hermione. She nodded.
He followed Snape inside.
The castle was quieter in the interior, the noise of the battle muffled to something distant and rhythmic. Snape moved at his usual pace, which was not accommodating, and Harry matched it without asking questions, because the set of Snape's shoulders told him that asking questions right now would not help anyone.
The headmaster's office. Snape opened a panel in the back wall — the one Kevin had shown Harry existed, in second year, though Kevin had opened it with more ceremony — and took out the Pensieve. From his breast pocket he produced a vial of silver-grey threads, dense and moving.
He set both on the desk. He looked at Harry.
For a moment neither of them spoke.
"The headmaster says this is your choice," Snape said. "He was very clear about that."
He took the stopper from the vial and poured the memories into the stone basin, and stepped back.
Harry looked at the swirling surface. Then he leaned in.
The memory was grey and still, the way all memories looked from outside.
Dumbledore was sitting at his desk alone. He looked up at Harry — looked through Harry, with the particular directness of someone who had prepared this message knowing it might be received by someone in distress, and had tried to account for that.
"Harry. If you're watching this, we've reached the point where there's no more room for me to be gentle about it."
He folded his hands. His voice was steady and unhurried, the way it always was when he was about to say something that couldn't be taken back.
"There is a fragment of Voldemort's soul inside you. Has been since you were fifteen months old — since the night Lily's sacrifice rebounded his Killing Curse and tore away a piece of his soul. That piece needed somewhere to go. You were the only living thing in the room."
Harry stood very still in the grey light of the memory.
"You are an accidental Horcrux, Harry. You didn't choose it. You couldn't have prevented it. And I want you to understand — this isn't a death sentence. But it is a complication."
Dumbledore was quiet for a moment.
"The only clean solution I can see is to let Voldemort do it himself. Allow him to cast the Killing Curse at you, with his own soul intact — I calculated this carefully, and I believe — I believe — that Lily's protection still resonates in his blood, in the way he used your blood to reconstitute himself in fourth year. I believe the Killing Curse will interact with the soul fragment in you the same way it interacted with Voldemort himself the night you were a child. I believe the fragment will die, and you will not."
A pause.
"But it is a theory. And I know — I know — that it is a great deal to ask of you."
The memory faded.
Harry came back to himself with his hands on the edge of the Pensieve and his breathing uneven.
Snape was still there. Still waiting.
"Kevin knows a soul-severing spell," Harry said. He wasn't really asking — he'd worked it out while he was still in the memory, had heard the echo of Kevin's voice over the Christmas break — give me your hand — and understood what it had been for. "He's been trying to find the Horcrux in me with it. Cut it out without killing me."
"He has," Snape said. "He hasn't had sufficient precision to locate it. The target is too small and too deeply integrated."
Harry looked at him. "But if Voldemort casts the curse himself, the resonance does the work for him."
"That is the headmaster's theory."
"And if the theory is wrong?"
Snape said nothing.
Harry almost laughed. There it was. The whole shape of it, finally clear.
He'd spent five years watching Kevin restructure this world piece by piece — pulling people back from the fates they'd been given, replacing the worst of what was supposed to happen with something different and better. Cedric alive. Sirius alive. Fred, still laughing somewhere in the castle right now. Kevin had done that, all of it, because he'd known what was coming and had refused to let it happen unchanged.
And now here was the one thing Kevin couldn't change for him.
Because it was his.
"Tell me where Voldemort is," Harry said.
The valley had been fighting for some time before Harry arrived.
Kevin had driven Voldemort through the wreckage of the cursed array three times by then. Each pass with the sword cost Voldemort something — not blood, not flesh, but the ability to concentrate, to hold his full power in a coherent shape. The soul-cuts accumulated. His spellwork had begun to stutter at the edges.
Which was when he resorted to sheer volume.
Fire spears by the dozen, lightning spears answering them, the valley walls shaking with the sustained back-and-forth of it. Kevin deflected and pressed in, deflected and pressed in, working the distance with a patience that had outlasted his irritation.
The voice came from behind him.
"Kevin!"
Kevin spun.
Harry stood at the valley entrance, wand in hand, the Sword of Gryffindor conspicuously absent from his grip since Kevin still had it.
Voldemort's next barrage was already incoming. Kevin turned back and caught it.
"What are you doing here?" he called across the distance, trying to put enough edge into it to communicate that this was not a question but an instruction to leave.
"I know what I am," Harry said. Quite clearly. "I know what has to happen."
Kevin caught the next three spears on the sword and looked at Harry's face.
He was not bluffing. He was not impulsive. He had the particular steadiness of someone who has done the arithmetic and arrived at an answer they intend to honour.
Kevin's chest went tight.
"You don't have to —"
"Kevin." Harry met his eyes. "Tell Ginny I'm sorry, if it goes wrong."
The mountain shook.
There was nothing to say to that. Kevin turned back to the fight, and Harry moved to his side.