An hour or so later, Leo was sitting in Professor McGonagall's office accompanied by everyone who had escaped from the chamber (thanks, apparently, to Dumbledore's phoenix, the Sorting Hat and the corrosive powers of Basilisk venom.

The explanation of what had actually been going on all these months made an awful lot of sense, and Leo was wondering why he hadn't realised it before, and why he hadn't made more of an effort to get hold of that diary before Marisa had been attacked.

"Now," said Professor Dumbledore finally to Harry and Ron, when almost everything had been discussed and sorted out. "I seem to remember saying I would have to expel the two of you if you broke any rules."

Harry and Ron gaped at him.

"Which goes to show that even the best of us can be forced to eat our words. I am going to award all three of you Special Awards for Services to the School, and… let me see, two hundred points each to your Houses."

Leo found himself smiling. He hadn't expected this to happen, but it was nice to know that Professor Dumbledore wasn't actually completely biased in favour of Gryffindors. And it would certainly guarantee Slytherin second place ahead of Ravenclaw in the House Cup.

"There's one thing I don't understand," said Potter. "How did Ginny end up with the diary?"

And then Leo realised. It should have been obvious, but there was no time to say it because the door burst violently open and in stalked Lucius Malfoy, Dobby the house-elf cowering beneath his arm.

"Good evening, Lucius," said Dumbledore pleasantly.

Lucius's eyes shot briefly to Leo, as if wondering why he was there, but then returned to Dumbledore. "So! You've come back. The governors suspended you, but you still saw fit to return to Hogwarts."

"Well, you see, the other eleven governors contacted me today. It was something like being caught in a hailstorm of owls, to tell the truth. They'd heard that Arthur Weasley's daughter had been killed and wanted me back at once. They seemed to think I was the best man for the job, after all. Very strange tales they told me, too. Several of them seemed to think that you had threatened to curse their families if they didn't agree to suspend me in the first place."

Leo was horrified at these accusations. Surely, surely it couldn't be true… but it did make sense, and it was just the sort of thing Lucius might have tried.

"So," sneered Lucius, refusing to react to the accusations, "have you stopped the attacks yet? Have you caught the culprit?"

"We have."

"Well? Who is it?"

"The same person as last time, Lucius. But this time Lord Voldemort was acting through someone else. By means of this diary." Dumbledore held up the little black book with a hole in to show him.

Leo scrutinised Lucius's reactions intently.

"I see."

"A clever plan. Because if these three students here – "

Leo's heart gave a little thump: he hadn't thought once about the consequences of thwarting his adoptive father's plot, but he quickly realised that he would soon be facing serious problems.

"– hadn't discovered this book, why – Ginny Weasley might have taken all of the blame. No one would ever have been able to prove that she hadn't acted of her own free will… and imagine what might have happened then. The Weasleys are one of our most prominent pure-blood families. Imagine the effect on Arthur Weasley and his Muggle Protection Act, if his own daughter was discovered attacking and killing Muggle-borns. Very fortunate the diary was discovered, and Riddle's memories wiped from it. Who knows what the consequences might have been otherwise…?"

All the time Dumbledore had been speaking, Dobby was miming something for Harry's benefit.

"Very fortunate," said Lucius stiffly.

Harry had finally worked it out. "Don't you want to know how Ginny got hold of that diary, Mr Malfoy?"

"How should I know how the stupid little girl got hold of it?"

"Because you gave it to her. In Flourish and Blotts. You picked up her old Transfiguration book and slipped the diary into it, didn't you?"

"Prove it," hissed Lucius.

"Oh, no-one will be able to do that," said Dumbledore, smiling. "Not now Riddle has vanished from the book. On the other hand, I would advise you, Lucius, not to go giving out any more of Lord Voldemort's old school things. If any more of them find their way into innocent hands, I think Arthur Weasley, for one, will make sure they are traced back to you."

"Dobby," snapped Lucius, "we're leaving. Asriel, come with me."

Leo stood apprehensively. There would be no time to work out how he wanted to spin this to best please Lucius: he'd have to make it up as he went along.