“Our headmaster is taking a short break,

“Our headmaster is taking a short break,“ said Professor McGonagall, pointing at the Snape-shaped hole in the window.

“Professor!” Harry shouted his hand on his forehead, He could see the Inferi-filled lake sliding beneath him, and he felt a ghostly green boat bump into the underground shore, and Voldemort lept from it with murder in his heart–

“Professor, we’ve got to barricade the school, he’s coming now!“

“Very well. He-Who-Must-Not-Be-Named is coming,” she told the other teachers. Sprout and Flitwick gasped. Slughorn let out a low groan. “Potter has work to do in the castle on Dumbledore’s orders. We need to put in place every protection of which we are capable while Potter does what he needs to do.”

“You realize , of course, that nothing we do will be able to keep out You-Know-Who indefinitely?” squeaked Flitwick.

“But we can hold him up.” said Professor Sprout.

“Thank you, Pomona,” said Professor McGonagall, and between the two witches there passed a look of grim understanding.

“I suggest we establish basic protection around the place, then gather our students and meet in the Great Hall. Most must be evacuated, though if any of those who are over age wish to stay and fight, I think they ought to be given the chance.“

“Agreed,” said Professor Sprout, already hurrying toward the door. “I shall meet you in the Great Hall in twenty minutes with my House.”

And as she jogged out of sight, they could hear her muttering, “Tentacula, Devil’s Snare. And Snargaluff pods…yes, I’d like to see the Death Eaters fighting those.”

“I can act from here,” said Flitwick, and although he could barely see out of it, he pointed his wand through the smashed window and started muttering incantations of great complexity. Harry heard a weird rushing noise, as though Flitwick had unleashed the power of the wind into the grounds.

“Professor,” Harry said, approaching the little Charms master. “Professor, I’m sorry to interrupt, but this is important. Have you got any idea where the diadem of Ravenclaw is?”

“–Protego Horribillis – the diadem of Ravenclaw?“ squeaked Flitwick. ”A little extra wisdom never goes amiss, Potter, but I hardly think it would be much use in this situation!“

“I only meant – do you know where it is? Have you ever seen it?”

“Seen it! Nobody has seen it in living memory! Long since lost, boy.”

Harry felt a mixture of desperate disappointment and panic. What, then, was the Horcrux?

“We shall meet you and your Ravenclaws in the Great Hall, Filius!“ said Professor McGonagall, beckoning to Harry and Luna to follow her.

They had just reached the door when Slughorn rumbled into speech.

“My word,“ he puffed, pale and sweaty, his walrus mustache aquiver. ”What a to-do! I’m not at all sure whether this is wise, Minerva. He is bound to find a way in, you know, and anyone who has tried to delay him will be in the most grievous peril–“

“I shall expect you and the Slytherins in the Great Hall in twenty minutes also.” said Professor McGonagall. “If you wish to leave with your students, we shall not stop you. But if any of you attempt to sabotage our resistance or take up arms against us within this castle, then, Horace, we duel to kill.”

“Minerva!” he said, aghast.

“The time has come for Slytherin House to decide upon its loyalties,“ interrupted Professor McGonagall. ”Go and wake your students, Horace.“

Harry did not stay to watch Slughorn splutter. He and Luna stayed after Professor McGonagall, who had taken up a position in the middle of the corridor and raised her wand.

“Piertotum–oh, for heaven’s sake, Filch, not now–“

The aged caretaker had just come hobbling into view, shouting “Students out of bed! Students in the corridors!”

“They’re supposed to be you blithering idiot!“ shouted McGonagall. ”Now go and do something constructive! Find Peeves!“