Tom did not bother with decoys this time. He pushed his wand straight into the water.
Gold light poured from the tip and spread through the lake, and the whole surface lit up, throwing bright scattered reflections across the cave ceiling. Every remaining Inferius snapped awake at once and began converging on the island from all directions.
Tom looked back over his shoulder. "Professor, stop watching and help. Sooner we finish, sooner we leave."
Dumbledore produced the Elder Wand with the expression of a man who has accepted his situation, and began knocking Inferi unconscious in wide sweeps. Nicolas roped them as they surfaced. Newt received them into the case.
With Dumbledore added to the line, the pace increased considerably. Tom made a rough count when it was done. Somewhere around two thousand, which would keep him and Nicolas occupied for a substantial stretch of time.
They made their way back to the shore. Sirius had composed himself, at least outwardly. Nothing showed on his face when they returned.
Dumbledore gave him and Lupin a small nod, did not produce the locket immediately, and waited until they were back at Grimmauld Place before handing it over.
Sirius's hands were shaking when he opened it. Inside, folded once, was a piece of parchment. More than a decade in the basin had started to yellow the edges.
He unfolded it slowly, read the first line, and his eyes went red again. He read it aloud, and his voice did not stay entirely steady.
"To the Dark Lord.
I know I will be dead long before you read this, but I want you to know that it was I who discovered your secret. I have stolen the real Horcrux and intend to destroy it as soon as I can. I face death in the hope that when you meet your match, you will be mortal once more.
R.A.B."
"Young master!"
Kreacher's cry came from somewhere low, a sound not quite like anything he had made before, and he dropped to his knees on the floor.
"A true hero," Dumbledore said. He was not performing reverence. It was simply there. "Regulus faced death without a trace of fear. Only contempt for Voldemort, and pride in what he had chosen to do."
"Good boy," Nicolas said quietly.
He turned toward the fireplace with Tom and Newt and stepped through.
Back at Tom's house, the three of them climbed into the case to survey the collection. Even Newt, who had spent decades surrounded by creatures that would alarm most people, went slightly still looking at two thousand Inferi lined up inside his suitcase. If they were left near the habitat sections, the contamination would spread quickly.
"I'm starting to have doubts about your plan," Nicolas muttered. "Even if you can extract the spiritual essence, are you certain you won't just end up with an alchemical creature whose only instinct is destruction?"
"It should be fine." Tom leaned against the case wall, thinking it through. "Inferi can be purified. There's a window between the purification completing and the full release, and that's when you do the extraction. In plain terms, you harvest just before the end."
Both old men stared at him.
"So," Nicolas said, slowly, "you're telling me we still need to run the purification process first before we can even begin the experiment?"
"Not we. You." Tom corrected him. Nicolas's eyes went wide. "I have more pressing research underway. This entire acquisition was to give you material to work with. Consider it a gift. Make the most of it."
He had not finished the sentence before he was gone, vanished without further ceremony.
Nicolas turned to Newt.
"Are we. Did that child just. We walked into this ourselves, didn't we."
Newt gave the helpless smile of someone who has known the answer for some time. "More or less. And we did it voluntarily."
Nicolas made several observations about Tom's character, none of them suitable for polite company, and finished with: "Voldemort calls himself a Dark Lord. The real menace is Tom Riddle."
But the anger had a ceiling. Refusing to work, actually stopping, was something Nicolas could not bring himself to do. It was not that Tom had charmed him into compliance. It was the problem itself, the genuine possibility of creating an alchemical life form from extracted consciousness, and the fact that two thousand Inferi were sitting in a suitcase in the next room waiting for someone to begin.
You could resent the person who put you in front of an interesting question and still be incapable of walking away from it.
"What if," Newt said, after a pause, "we asked Dumbledore for help? He'll need to purify Regulus anyway. The difference between purifying one and purifying several hundred is really just time. Tom has a saying for this, doesn't he. Something about those who are capable carrying the load."
Nicolas looked at him for a long moment.
"Newt," he said. "Tom has corrupted you completely."