Harry Potter and the Half-Blood Prince

“I don’t know exactly how it happened,” said Professor McGonagall distractedly. “It’s all so confusing… Dumbledore had told us that he would be leaving the school for a few hours and that we were to patrol the corridors just in case… Remus, Bill, and Nymphadora were to join us… and so we patrolled. All seemed quiet. Every secret passageway out of the school was covered. We knew nobody could fly in. There were powerful enchantments on every entrance into the castle. I still don’t know how the Death Eaters can possibly have entered…”

“I do,” said Harry, and he explained, briefly, about the pair of Vanishing Cabinets and the magical pathway they formed. “So they got in through the Room of Requirement.”

Almost against his will he glanced from Ron to Hermione, both of whom looked devastated.

“I messed up, Harry,” said Ron bleakly. “We did like you told us: We checked the Marauder’s Map and we couldn’t see Malfoy on it, so we thought he must be in the Room of Requirement, so me, Ginny, and Neville went to keep watch on it… but Malfoy got past us.”

“He came out of the room about an hour after we started keeping watch,” said Ginny. “He was on his own, clutching that awful shriveled arm—”

“His Hand of Glory,” said Ron. “Gives light only to the holder, remember?”

“Anyway,” Ginny went on, “he must have been checking whether the coast was clear to let the Death Eaters out, because the moment he saw us he threw something into the air and it all went pitch-black—”

“—Peruvian Instant Darkness Powder,” said Ron bitterly. “Fred and George’s. I’m going to be having a word with them about who they let buy their products.”

“We tried everything, Lumos, Incendio,” said Ginny. “Nothing would penetrate the darkness; all we could do was grope our way out of the corridor again, and meanwhile we could hear people rushing past us. Obviously Malfoy could see because of that hand thing and was guiding them, but we didn’t dare use any curses or anything in case we hit each other, and by the time we’d reached a corridor that was light, they’d gone.”

“Luckily,” said Lupin hoarsely, “Ron, Ginny, and Neville ran into us almost immediately and told us what had happened. We found the Death Eaters minutes later, heading in the direction of the Astronomy Tower. Malfoy obviously hadn’t expected more people to be on the watch; he seemed to have exhausted his supply of Darkness Powder, at any rate. A fight broke out, they scattered and we gave chase. One of them, Gibbon, broke away and headed up the tower stairs—”

“To set off the Mark?” asked Harry.

“He must have done, yes, they must have arranged that before they left the Room of Requirement,” said Lupin. “But I don’t think Gibbon liked the idea of waiting up there alone for Dumbledore, because he came running back downstairs to rejoin the fight and was hit by a Killing Curse that just missed me.”

“So if Ron was watching the Room of Requirement with Ginny and Neville,” said Harry, turning to Hermione, “were you—?”

“Outside Snape’s office, yes,” whispered Hermione, her eyes sparkling with tears, “with Luna. We hung around for ages outside it and nothing happened… We didn’t know what was going on upstairs, Ron had taken the map—It was nearly midnight when Professor Flitwick came sprinting down into the dungeons. He was shouting about Death Eaters in the castle, I don’t think he really registered that Luna and I were there at all, he just burst his way into Snape’s office and we heard him saying that Snape had to go back with him and help and then we heard a loud thump and Snape came hurtling out of his room and he saw us and—and—”

“What?” Harry urged her.

“I was so stupid, Harry!” said Hermione in a high-pitched whisper. “He said Professor Flitwick had collapsed and that we should go and take care of him while he—while he went to help fight the Death Eaters—”

She covered her face in shame and continued to talk into her fingers, so that her voice was muffled. “We went into his office to see if we could help Professor Flitwick and found him unconscious on the floor… and oh, it’s so obvious now, Snape must have Stupefied Flitwick, but we didn’t realize, Harry, we didn’t realize, we just let Snape go!”

“It’s not your fault,” said Lupin firmly. “Hermione, had you not obeyed Snape and got out of the way, he probably would have killed you and Luna.”

“So then he came upstairs,” said Harry, who was watching Snape running up the marble staircase in his mind’s eye, his black robes billowing behind him as ever, pulling his wand from under his cloak as he ascended, “and he found the place where you were all fighting…”