Professor Dumbledore sent all the Gryffindors back to the Great Hall, where they were joined ten minutes later by the students from Hufflepuff, Ravenclaw, and Slytherin, who all looked extremely confused.

"The teachers and I need to conduct a thorough search of the castle," Professor Dumbledore told them as Professors McGonagall and Flitwick closed all doors into the hall. "I'm afraid that, for your own safety, you will have to spend the night here. I want the prefects to stand guard over the entrances to the hall and I am leaving the Head Boy and Girl in charge. Any disturbance should be reported to me immediately," he added to Percy, who was looking immensely proud and important. "Send word with one of the ghosts."

Professor Dumbledore paused, about to leave the hall, and said, "Oh, yes, you'll be needing..."

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