One casual wave of his wand and the long tables flew to the edges of the hall and stood themselves against the walls; another wave, and the floor was covered with hundreds of squashy purple sleeping bags.

“Sleep well,” said Professor Dumbledore, closing the door behind him.

The hall immediately began to buzz excitedly; the Gryffindors were telling the rest of the school what had just happened.

“Everyone into their sleeping bags!” shouted Percy. “Come on, now, no more talking! Lights out in ten minutes!”

“C’mon,” Ron said to Harry and Hermione; they seized three sleeping bags and dragged them into a corner.

“Do you think Black’s still in the castle?” Hermione whispered anxiously.

“Dumbledore obviously thinks he might be,” said Ron.

“It’s very lucky he picked tonight, you know,” said Hermione as they climbed fully dressed into their sleeping bags and propped themselves on their elbows to talk. “The one night we weren’t in the tower . . . ”

“I reckon he’s lost track of time, being on the run,” said Ron. “Didn’t realize it was Halloween. Otherwise he’d have come bursting in here.”

Hermione shuddered.

All around them, people were asking one another the same question: “How did he get in?”

“Maybe he knows how to Apparate,” said a Ravenclaw a few feet away. “Just appear out of thin air, you know.”

“Disguised himself, probably,” said a Hufflepuff fifth year.

“He could’ve flown in,” suggested Dean Thomas.

“Honestly, am I the only person who’s ever bothered to read Hogwarts, A History?” said Hermione crossly to Harry and Ron.

“Probably,” said Ron. “Why?”

“Because the castle’s protected by more than walls, you know,” said Hermione. “There are all sorts of enchantments on it, to stop people entering by stealth. You can’t just Apparate in here. And I’d like to see the disguise that could fool those dementors. They’re guarding every single entrance to the grounds. They’d have seen him fly in too. And Filch knows all the secret passages, they’ll have them covered . . . ”

“The lights are going out now!” Percy shouted. “I want everyone in their sleeping bags and no more talking!”

The candles all went out at once. The only light now came from the silvery ghosts, who were drifting about talking seriously to the prefects, and the enchanted ceiling, which, like the sky outside, was scattered with stars. What with that, and the whispering that still filled the hall, Harry felt as though he were sleeping outdoors in a light wind.