He paused, and Harry remembered what Mr. Weasley had said about Dumbledore not being happy with the dementors guarding the school.

"They are stationed at every entrance to the grounds," Dumbledore continued, "and while they are with us, I must make it plain that nobody is to leave school without permission. Dementors are not to be fooled by tricks or disguises -- or even Invisibility Cloaks," he added blandly,
and Harry and Ron glanced at each other. "Or powers of invisibility." Amelia looked away.  "It is not in the nature of a dementor to understand pleading or excuses. I therefore warn each and every one of you to give them no reason to harm you. I look to the prefects, and our new Head Boy and Girl, to make sure that no student runs afoul of the dementors," he said.

Percy, who was sitting a few seats down from Harry, puffed out his chest again and stared around impressively. Dumbledore paused again; he looked very seriously around the hall, and nobody moved or made a sound.

"On a happier note," he continued, I am pleased to welcome two new teachers to our ranks this year.

"First, Professor Lupin, who has kindly consented to fill the post of Defense Against the Dark Arts teacher."

There was some scattered, rather unenthusiastic applause. Only those who had been in the compartment on the train with Professor Lupin clapped hard, Harry among them. Professor Lupin looked particularly shabby next to all the other teachers in their best robes.

"Look at Snape!" Ron hissed in Harry's ear.

Professor Snape, the Potions master, was staring along the staff table at Professor Lupin. It was common knowledge that Snape ,anted the Defense Against the Dark Arts job, but even Harry, who hated Snape, was startled at the expression twisting his thin, sallow face. it was beyond anger: it was loathing. Harry knew that expression only too well; it was the look Snape wore every time he set eyes on Harry.

"Did Profoser Lupin piss in his Cheerios? I haven't seen Snape that mad since I blew up the potions lab," whispered Amelia to Hermione.

"As to our second new appointment," Dumbledore continued as the lukewarm applause for Professor Lupin died away. "Well, I am sorry to tell you