J. Rowling - Harry Potter and the Half-Blood Prince

“—more Death Eaters arrived—and then Snape—and Snape did it. The Avada Kedavra.”

Harry couldn’t go on.

Madam Pomfrey burst into tears. Nobody paid her any attention except Ginny, who whispered, “Shh! Listen!”

Gulping, Madam Pomfrey pressed her fingers to her mouth, her eyes wide. Somewhere out in the darkness, a phoenix was singing in a way Harry had never heard before: a stricken lament of terrible beauty. And Harry felt, as he had felt about phoenix song before, that the music was inside him, not without: It was his own grief turned magically to song that echoed across the grounds and through the castle windows.

How long they all stood there, listening, he did not know, nor why it seemed to ease their pain a little to listen to the sound of their mourning, but it felt like a long time later that the hospital door opened again and Professor McGonagall entered the ward. Like all the rest, she bore marks of the recent battle: There were grazes on her face and her robes were ripped.

“Molly and Arthur are on their way,” she said, and the spell of the music was broken: Everyone roused themselves as though coming out of trances, turning again to look at Bill, or else to rub their own eyest shake their heads. “Harry, what happened? According to Hagrid you were with Professor Dumbledore when he—when it happened. He says Professor Snape was involved in some—”

“Snape killed Dumbledore,” said Harry.

She stared at him for a moment, then swayed alarmingly; Madam Pomfrey, who seemed to have pulled herself together, ran forward, conjuring a chair from thin air, which she pushed under McGonagall.

“Snape,” repeated McGonagall faintly, falling into the chair. “We all wondered… but he trusted… always… Snape… I can’t believe it…”

“Snape was a highly accomplished Occlumens,” said Lupin, his voice uncharacteristically harsh. “We always knew that.”

“But Dumbledore swore he was on our side!” whispered Tonks. “I always thought Dumbledore must know something about Snape that we didn’t…”

“He always hinted that he had an ironclad reason for trusting Snape,” muttered Professor McGonagall, now dabbing at the corners of her leaking eyes with a tartan-edged handkerchief. “I mean… with Snape’s history… of course people were bound to wonder… but Dumbledore told me explicitly that Snape’s repentance was absolutely genuine—Wouldn’t hear a word against him!”

“I’d love to know what Snape told him to convince him,” said Tonks.

“I know,” said Harry, and they all turned to look at him. “Snape passed Voldemort the information that made Voldemort hunt down my mum and dad. Then Snape told Dumbledore he hadn’t realized what he was doing, he was really sorry he’d done it, sorry that they were dead.”

They all stared at him.

“And Dumbledore believed that?” said Lupin incredulously. “Dumbledore believed Snape was sorry James was dead? Snape hated James…”

“And he didn’t think my mother was worth a damn either,” said Harry, “because she was Muggle-born… ‘Mudblood,’ he called her…”

Nobody asked how Harry knew this. All of them seemed to be lost in horrified shock, trying to digest the monstrous truth of what had happened.

“This is all my fault,” said Professor McGonagall suddenly. She looked disoriented, twisting her wet handkerchief in her hands. “My fault. I sent Filius to fetch Snape tonight, I actually sent for him to come and help us! If I hadn’t alerted Snape to what was going on, he might never have joined forces with the Death Eaters. I don’t think he knew they were there before Filius told him, I don’t think he knew they were coming.”

“It isn’t your fault, Minerva,” said Lupin firmly. “We all wanted more help, we were glad to think Snape was on his way…”

“So when he arrived at the fight, he joined in on the Death Eaters’ side?” asked Harry, who wanted every detail of Snape’s duplicity and infamy, feverishly collecting more reasons to hate him, to swear vengeance.

“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—”