There was a brief silence in the room, except for the two goblin guards who went on breathing regardless.
"You are mad," Lucius Malfoy said coldly.
"It's called justice, Lord Malfoy. You cannot possibly expect me to cooperate with you while you are holding the wealth of House Potter under what you now know to be false pretenses. I understand how it looked to you at the time, but you know better now."
"You have nothing to offer me worth a hundred thousand Galleons."
"Don't I?" Harry said distantly. "I wonder. I think it quite probable that you care more about the long-term welfare of House Malfoy than about whichever political issue the last generation's failed Dark Lord made his personal hobbyhorse." Harry glanced significantly at Draco. "The next generation is drawing its own battle lines and forming new alliances. Your son can be frozen out of that, or he can go straight to the top. Is that worth more to you than forty thousand Galleons you weren't particularly expecting and don't particularly need?" Harry smiled thinly. "Forty thousand Galleons. Two million Muggle pounds sterling. Your son knows some things about the size of the Muggle economy that might surprise you. They'd find it amusing, that the fate of a country was revolving around two million pounds sterling. They'd think it was cute. And I think much the same, Lord Malfoy. This isn't about me being desperate. This is about you getting a fair chance to be fair."
"Oh?" said Lord Malfoy. "And if I refuse your fair chance, what then?"
Harry shrugged. "Depends what sort of coalition government gets put together without the Malfoys. If the government can be reformed peacefully and it would disturb the peace to do otherwise, I'll pay you the money out of petty cash. Or maybe the Death Eaters will be retried for past crimes and executed as a matter of justice, as a result of due legal process, of course."
"You truly are mad," Lucius Malfoy said quietly. "You have no power, no wealth, and yet you say such things to me."
"Yes, it's silly to think I could scare you. After all, you're not a Dementor."
And Harry went on smiling. He'd looked it up, and apparently a bezoar would heal almost any poison if you shoved it into someone's mouth fast enough. Maybe that wouldn't repair radiation damage from Transfigured polonium, but then again, maybe it would. So Harry had looked up the freezing points of various acids, and it turned out that sulfuric acid would freeze at just ten degrees Celsius, which meant Harry could buy a liter of acid on the Muggle market, freeze it solid, and Transfigure it down to a tiny little unnoticable water-ice chip to be flipped into someone's mouth and ingested. No bezoar would compensate for that, once the Transfiguration wore off. Harry had no intention of saying it out loud, of course, but now that he'd failed decisively to prevent any deaths during his quest, he had no further intention of being restrained by the law or even the code of Batman.
Last chance to live, Lucius. Ethically speaking, your life was bought and paid for the day you committed your first atrocity for the Death Eaters. You're still human and your life still has intrinsic value, but you no longer have the deontological protection of an innocent. Any good person is licensed to kill you now, if they think it'll save net lives in the long run; and I will conclude as much of you, if you begin to get in my way. Whoever sent the troll after Granger must have targeted you too and hit you with some curse that makes former Death Eaters melt into a pile of goo. Very sad.
"Father," Draco said in a small voice. "I think you should consider it, father."
Lucius Malfoy looked at his son. "You jest."
"It's true. I don't think Potter just made up his books, nobody could have written all that and there were things in them that I could check for myself. And if even half of all that is true, he's right, a hundred thousand Galleons won't mean much. If we give it to him he really will be friends with House Malfoy again - the way he thinks of being friends, anyway. And if we don't, he'll be your enemy, whether it's in his own interests or not, he'll just go after you. Harry Potter really does think like that. It's not about money to him, it's about what he thinks is honor."
Harry Potter inclined his head, still smiling.
"But let's get one part of it straight," Draco said, now staring directly at him. There was a fierce light in his eyes. "You wronged me. And you owe me."
"Acknowledged," Harry said quietly. "Conditional on the rest of it, of course."
Lucius Malfoy opened his mouth to say who-knew-what and then closed it again. "Mad," he said again.
There was a long father-and-son argument during which Harry managed to keep his mouth shut.
When it seemed that even Draco wouldn't be able to persuade his father, Harry spoke up again, and proposed his intended next steps, if the Houses of Potter and Malfoy could cooperate.
Then came more argument between Lucius and Draco, during which Harry again stayed silent.
Finally Lucius Malfoy's eyes turned to gaze at Harry. "And you believe," Lucius Malfoy said, "that you can persuade Longbottom and Bones to go along with this notion, even if Dumbledore opposes it."
Harry nodded. "They'll be suspicious of your involvement, of course. But I'll tell them that it was my plan to start with, and that should help."
"I suppose," Lucius Malfoy said after a pause, "that I could have a contract drawn up, absolving you of almost all the remaining debt, if by some chance I do go along with this mad idea. It shall need more guarantees, of course -"
Harry promptly reached into his robes and drew out a parchment, unfolding it and spreading it across the golden table. "I've taken the liberty myself, actually," Harry said. He'd spent some careful hours in the Hogwarts library with the law books available. Thankfully, so far as Harry could tell, the laws of magical Britain were charmingly simple by Muggle standards. Writing that the original blood debt and payment was cancelled, the Potters' wealth and all other vault items would be returned, and the remaining debt annulled, all with no fault to the Malfoys, was only a few more lines than it took to say out loud. "I had to promise my keepers not to sign anything you gave me. So I made sure to compose this myself, and sign it before I left."
Draco emitted a choked laugh.
Lucius read through the contract, smiling humorlessly. "How charmingly straightforward."
"I also promised not to touch a quill while I was in Gringotts," Harry said. He reached into his robes again and drew out a Muggle pen, along with a sheet of normal paper. "Will this wording be all right?" Harry rapidly scribbled down a legal-sounding statement to the effect that House Potter didn't hold House Malfoy responsible in any way for Hermione Granger's murder and didn't believe they had anything to do with it, then held up the paper in the air for Lord Malfoy's inspection.
Lord Malfoy looked at the paper, rolled his eyes slightly, and said, "Good enough, I suppose. Though to have the proper meaning, you should use the legal term indemnify rather than exonerate -"
"Nice try, but no. I know exactly what that word means, Lord Malfoy." Harry took his parchment and began copying down his original wording more carefully.
When Harry was done, Lord Malfoy reached across the golden table and took the pen, looking at it thoughtfully. "One of your Muggle artefacts, I suppose? What does this do, son?"
"It writes without needing an inkwell," Draco answered.