Dumbledore closed his eyes again and nodded, as though he was about to fall asleep.
“…of course… Rosmerta. How long has she been under the Imperius Curse?”
“Got there at last, have you?” Malfoy taunted.
There was another yell from below, rather louder than the last. Malfoy looked nervously over his shoulder again, then back at Dumbledore, who went on, “So poor Rosmerta was forced to lurk in her own bathroom and pass that necklace to any Hogwarts student who entered the room unaccompanied? And the poisoned mead… well, naturally, Rosmerta was able to poison it for you before she sent the bottle to Slughorn, believing that it was to be my Christmas present… yes, very neat… very neat… poor Mr. Filch would not, of course, think to check a bottle of Rosmerta’s… tell me, how have you been communicating with Rosmerta? I thought we had all methods of communication in and out of the school monitored.”
“Enchanted coins,” said Malfoy, as though he was compelled to keep talking, though his wand hand was shaking badly. “I had one and she had the other and I could send her messages—”
“Isn’t that the secret method of communication the group that called themselves Dumbledore’s Army used last year?” asked Dumbledore. His voice was light and conversational, but Harry saw him slip an inch lower down the wall as he said it.
“Yeah, I got the idea from them,” said Malfoy, with a twisted smile. “I got the idea of poisoning the mead from the Mudblood Granger, as well, I heard her talking in the library about Filch not recognising potions…”
“Please do not use that offensive word in front of me,” said Dumbledore.
Malfoy gave a harsh laugh.
“You care about me saying ‘Mudblood’ when I’m about to kill you?”
“Yes, I do,” said Dumbledore, and Harry saw his feet slide a little on the floor as he struggled to remain upright. “But as for being about to kill me, Draco, you have had several long minutes now. We are quite alone. I am more defenceless than you can have dreamed of finding me, and still you have not acted…”