As she said it, a wrath that was like physical pain blazed through Harry, setting his scar on fire, and for a second he looked down upon a basin whose potion had turned clear, and saw that no golden locket lay safe beneath the surface—

“Potter, are you all right?” said a voice, and Harry came back. He was clutching Luna’s shoulder to steady himself.

“Time’s running out, Voldemort’s getting nearer. Professor, I’m acting on Dumbledore’s orders, I must find what he wanted me to find! But we’ve got to get the students out while I’m searching the castle—It’s me Voldemort wants, but he won’t care about killing a few more or less, not now—”

Not now he knows I’m attacking Horcruxes, Harry finished the sentence in his head.

“You’re acting on Dumbledore’s orders?” she repeated with a look of dawning wonder. Then she drew herself up to her fullest height.

“We shall secure the school against He-Who-Must-Not-Be-Named while you search for this—this object.”

“Is that possible?”

“I think so,” said Professor McGonagall dryly, “we teachers are rather good at magic, you know. I am sure we will be able to hold him off for a while if we all put our best efforts into it. Of course, something will have to be done about Professor Snape—”

“Let me—”

“—and if Hogwarts is about to enter a state of siege, with the Dark Lord at the gates, it would indeed be advisable to take as many innocent people out of the way as possible. With the Floo Network under observation, and Apparition impossible within the grounds—”

“There’s a way,” said Harry quickly, and he explained about the passageway leading into the Hog’s Head.

“Potter, we’re talking about hundreds of students—”

“I know, Professor, but if Voldemort and the Death Eaters are concentrating on the school boundaries they won’t be interested in anyone who’s Disapparating out of Hog’s Head.”

“There’s something in that,” she agreed. She pointed her wand at the Carrows, and a silver net fell upon their bound bodies, tied itself around them, and hoisted them into the air, where they dangled beneath the blue-and-gold ceiling like two large, ugly sea creatures. “Come. We must alert the other Heads of House. You’d better put that Cloak back on.”

She marched toward the door, and as she did so she raised her wand. From the tip burst three silver cats with spectacle markings around their eyes. The Patronuses ran sleekly ahead, filling the spiral staircase with silvery light, as Professor McGonagall, Harry, and Luna hurried back down.

Along the corridors they raced, and one by one the Patronuses left them. Professor McGonagall’s tartan dressing gown rustled over the floor, and Harry and Luna jogged behind her under the Cloak.

They had descended two more floors when another set of quiet joined theirs. Harry, whose scar was still prickling, heard them first. He felt in the pouch around his neck for the Marauder’s Map, but before he could take it our, McGonagall too seemed to become aware of their company. She halted, raised her wand ready to duel, and said, “Who’s there?”

“It is I,” said a low voice.

From behind a suit of armor stepped Severus Snape.

Hatred boiled up in Harry at the sight of him. He had forgotten the details of Snape’s appearance in the magnitude of his crimes, forgotten how his greasy black hair hung in curtains around his thin face, how his black eyes had a dead, cold look. He was not wearing nightclothes, but was dressed in his usual black cloak, and he too was holding his wand ready for a fight.

“Where are the Carrows?” he asked quietly.

“Wherever you told them to be, I expect, Severus,” said Professor McGonagall.

Snape stepped nearer, and his eyes flitted over Professor McGonagall into the air around her, as if he knew that Harry was there. Harry held his wand up too, ready to attack.

“I was under the impression,” said Snape, “that Alecto had apprehended an intruder.”

“Really?” said Professor McGonagall. “And what gave you that impression?”

Snape mad a slight flexing movement of his left arm, where the Dark Mark was branded into his skin.

“Oh, but naturally,” said Professor McGonagall. “You Death Eaters have your own private means of communication, I forgot.”

Snape pretended not to have heard her. His eyes were still probing the air all about her, and he was moving gradually closer, with an air of hardly noticing what he was doing.

“I did not know that it was your night to patrol the corridors, Minerva.”

“You have some objection?”

“I wonder what could have brought you out of our bed at this late hour?”

“I thought I heard a disturbance,” said Professor McGonagall.

“Really? But all seems calm.”

Snape looked into her eyes.

“Have you seen Harry Potter, Minerva? Because if you have, I must insist—”

Professor McGonagall moved faster than Harry could have believed. Her wand slashed through the air and for a split second Harry thought that Snape must crumple, unconscious, but the swiftness of his Shield Charm was such that McGonagall was thrown off balance. She brandished her wand at a touch on the wall and it flew out of its bracket. Harry, about to curse Snape, was forced to pull Luna out of the way of the descending flames, which became a ring of fire that filled the corridor and flew like a lasso at Snape—

Then it was no longer fire, but a great black serpent that McGonagall blasted to smoke, which re-formed and solidified in seconds to become a swarm of pursuing daggers. Snape avoided them only by forcing the suit of armor in front of him, and with echoing clangs the daggers sank, one after another, into its breast—

“Minerva!” said a squeaky voice, and looking behind him, still shielding Luna from flying spells, Harry saw Professors Flitwick and Sprout sprinting up the corridor toward them in their nightclothes, with the enormous Professor Slughorn panting along at the rear.

“No!” squealed Flitwick, raising his wand. “You’ll do no more murder at Hogwarts!”

Flitwick’s spell hit the suit of armor behind which Snape had taken shelter. With a clatter it came to life. Snape struggled free of the crushing arms and sent it flying back toward his attackers. Harry and Luna had to dive sideways to avoid it as it smashed into the wall and shattered. When Harry looked up again, Snape was in full flight, McGonagall, Flitwick, and Sprout all thundering after him. He hurtled through a classroom door and, moments later, he heard McGonagall cry, “Coward! COWARD!”

“What’s happened, what’s happened?” asked Luna.

Harry dragged her to her feet and they raced along the corridor, trailing the Invisibility Cloak behind them, into the deserted classroom where Professors McGonagall, Flitwick, and Sprout were standing at a smashed window.

“He jumped,” said Professor McGonagall as Harry and Luna ran into the room.

“You mean he’s dead?” Harry sprinted to the window, ignoring Flitwick’s and Sprout’s yells of shock at his sudden appearance.

“No, he’s not dead,” said McGonagall bitterly. “Unlike Dumbledore, he was still carrying a wand… and he seems to have learned a few tricks from his master.”

With a tingle of horror, Harry saw in the distance a huge, bat-like shape flying through the darkness toward the perimeter wall.

There were heavy footfalls behind them, and a great deal of puffing. Slughorn had just caught up.

“Harry!” he panted, massaging his immense chest beneath his emerald-green silk pajamas. “My dear boy… what a surprise… Minerva, do please explain… Severus… what…?”

“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—