"But why put the key in the room at all?" James demanded, leaning over Dumbledore's desk. "The Bluebeard lock is a fantastic idea. But why not keep the key somewhere else entirely? I mean, one good key-revealing charm and all anyone's got to be is a half-decent flyer!"

"My dear Professor Potter," said Dumbledore calmly, "perhaps you are forgetting that key-revealing charms do not work on a Bluebeard lock."

"Okay, but that doesn't preclude the possibility that someone with good eyes could nab it. And lock-revealing charms work on Bluebeard keys! Why not keep the key yourself? You've got all this stuff locked up around your office, like that Pensieve and the secret stash of sherbet lemons…"

"Both of which you appear to have discovered, Professor, and are you so certain you are the only wizard clever enough to find things I have hidden?" Dumbledore asked.

"All right, bad example. You don't literally have to keep it here, I just want to know why it's necessary to have the key in the same chamber with the door. Maybe Flitsy can keep it safe somewhere. We could lock it up, or…"

"We really are going to need to get the Stone out at some point," said Dumbledore, "and Professor Flitwick may not always be on hand when that need arises."

"Can we at least ensure that the trials would actually keep out someone trying to steal it, though? Like…I know. Add an extra charm so that when it's caught, it alerts you instantly. That way if someone you know is supposed to get it gets it, you won't have to worry, but if someone else is after it you can come stop them."

"Unfortunately, putting one charm on anything Bluebeard is complicated enough, according to Professor Flitwick. But such a charm is a good idea—you may put one on your contribution, if you wish."

"I wanted to talk to you about what my contribution might be."

After the brightness of the key chamber, the next room appeared pitch black, but when the door closed behind them (and after Malfoy hastily checked to make sure that it would open backward again) their eyes adjusted to the dim light. The chamber appeared quite empty; there was a heavy oak door at one end with a handle but no lock.

"Er," said Ron.

"Be careful," said Harry. "The floor could be trapped, or the walls could cave in, like in Star Wars…I'll go through first, follow where I step…"

"You're just volunteering to go first?" asked Malfoy. "This could be anything!"

"You want to go first, then?"

"No, but why on earth are you volunteering…?"

"Shut up, Malfoy," said Ron. "He's right, Harry, this could be anything, and we can't risk you. I'll go first."

"Don't be perfectly ridiculous," said Hermione. "I know more defensive spells than either of you. Anyway, Harry went first last time; it's time for someone else to take a turn."

"Right," said Ron, "me. You're both too valuable to lose, Hermione, I'll go first."

But Harry had already started off across the floor.

"You Gryffindors, honestly!" said Malfoy.

"Hermione, what's that light spell?" Harry called back.

"Which, Lumos?"

"Yeah, that."

With the little light that afforded, he was able to see the floor in front of him clearly. There were a few footmarks in the thick dust, and he stepped carefully into them. He made it all the way across the room without anything exploding, dripping on him, creaking ominously, or shooting out at him.

"It's all right," he said. "Just follow the footmarks. They forgot to clear them."

Malfoy, assured that he probably wasn't going to die, came first, and when they had all made it he strode forward and turned the door handle.

"Watch out, you id—!"

Before Ron could scream out a proper warning, the door flew open and a massive black shape flew out—what looked like an empty black cloak. Malfoy leapt backward and Ron swore.

Harry suddenly felt cold all over. The black shape turned to look at him and he felt the world ringing in his ears—he heard distant screaming from somewhere and his head felt light.

"What is that thing?!" he gasped.

Malfoy stood as if paralysed, staring at it. His mouth opened but no sounds came out.

"It's a bloody Dementor!" cried Ron. The shape turned to look at him, now, and he threw up his hands to shield himself.

"A what?! How do we get past it?!"

"I don't know!"

"Exp…Exp…" said Malfoy, waving his wand in circles. At the sound of his voice the Dementor turned to him and seemed to spread, growing larger and larger.

"Exp what?" shrieked Hermione.

Malfoy fell over backward, his face a mask of terror. "Think of something happy," he managed.

Harry felt as though he'd never be happy again.

"That's right," said Ron, and the massive shape began to glide toward him again. "Something happy, dad said, and there's something you have to say, Expectum…Expectorate…"

"Expecto Patronum," said Malfoy, a little louder now that the creature had turned away from him. "That's the incantation, Expecto Patronum, and you've got to focus on something happy, a happy memory…oh god oh god oh god…"

"I don't understand," said Hermione. "What is that? Why is it just standing there, why isn't it doing anything?"

It appeared to hear her, because it suddenly rushed toward her and emitted a horrifying shriek. She cried out and covered her head with her arms.

Something happy…

Harry leapt in the way and drew a huge circle in the air with his wand. "Expecto Patronum," he shouted.

A sort of thin silvery puff of vapour, about the size of a Snitch, came out of his wand and hung in the air between him and the black cloak. The Dementor paused and shook what would have been its head, as if to clear the stuff away, but the cloud followed. Then it flailed its hands, as though swatting aside an annoying bee.

"What's…what's it doing?" Malfoy asked in a high-pitched quaver completely unlike his usual drawl.

The Dementor moved backward and tripped over its robes.

"That's not a Dementor!" cried Ron suddenly.

"Don't be an idiot, Weasley, of course it's a Dementor!"

"No Dementor would act like that! It's only pretending!"

"So what the bloody hell is it?"

"It's a shapeshifter of some kind…I don't know, something that wants us to be scared…?"

"A boggart!" Hermione said.

"A what?" said Harry.

Malfoy leapt to his feet, looking immensely relieved. "A boggart, of course! Riddikulus!"

At his word, the bottom of the Dementor's robes disappeared, revealing two very skinny white legs with knobbly knees. The Dementor—boggart?—gave a little shriek and tried to pull its robes down, as if wanting to hide the legs. Harry and Ron cracked up laughing.

The thing whirled around to face Harry, studied him a moment, and then suddenly grew and transformed, with a flash of green light. Instead of a hood a head grew, a monstrous, distorted head, with two slits in the place of a nose, and glinting red eyes. The robes returned but now the thing was wielding a wand in one pale, bony hand, and the wand was pointed directly at Harry.

Harry had never in his memory seen the face, but he recognised it at once.

Lord Voldemort.

Hermione screamed. Malfoy screamed louder and higher. Harry shouted, "What do I do? What…?"

"Hey, boggy! Over here!" yelled Ron suddenly. He charged forward and gave the Dark Lord a kick with his slippered foot. It whirled at this and morphed into a gigantic multi-legged spider, larger than anything it had been so far. Ron yelped.

Malfoy appeared to regain his equilibrium. "Didn't mummy and daddy ever teach ickle Ronnikins how to deal with a boggart?" he jeered.

"R…R…" said Ron, then, gathering his courage, "Riddikulus!"

With a bang, the spider's legs all disappeared, leaving it hopping and wriggling in place.

They all stared. The spider rolled over three times in frustration.

"Ron, your, er, boggart," Harry said. "I think it was trying to scare you, but it really hasn't got…a leg to stand on."

"No," said Ron; "Malfoy's did, though."

Then they all began to laugh, out of relief at first, and then because the thing did look funny, helpless and hopping. The legless spider shrank and grew less distinct with each new wave of laughter, but before it could entirely fade it squirmed, stretched, and barrelled over toward Hermione. It morphed into Professor McGonagall, holding a piece of paper and looking very severe.

"Failed…everything!" cried McGonagall. Hermione looked shocked.

"It's all right, Hermione, just picture something funny," said Ron, who was still chuckling. "Picture it really clearly!"

"Disgrace to this school…immediately expelled!"

"Er…Riddikulus," said Hermione.

"Your parents will hear of this!"

"It's all right, just concentrate," said Ron. "Something funny."

"Riddikulus," Hermione repeated, loudly. With a snap, the boggart's clothes all disappeared, leaving it standing there in a ridiculous pink slip with red hearts all over it. It screamed, and so did Hermione.

But Ron doubled over with laughter. "How is that better?!" he howled.

Harry wailed as if in pain and hid his eyes, which made Hermione start to giggle, and then once she started she just couldn't stop until she toppled backward and lay supine and hysterical on the floor. Malfoy had actually collapsed on all fours, banging the ground with his fist.

The creature shrank almost out of view; when it tried to morph again, it simply disappeared.

"Hermione, you did brilliantly, well done," said Ron. "Laughter, mum always said…Come on, Malfoy."

"I…can't…breathe," said Malfoy.

The other three couldn't help but grin. Malfoy eventually collected himself enough to stand up, but he still spasmodically broke into bouts of laughter at the image of the severe Gryffindor Head in a pink slip with red hearts.

"I wouldn't have missed that for anything," he said.

"Why did you stay?" Harry wanted to know as they all approached the door, feeling much better. "You could've run."

"From a little boggart?"

"Er, from the Dementor. You seemed pretty terrified."

"I happened to have been reading a rather graphic account of some Dementor victims last night. There is very real danger there! They can be so…undiscriminating."

"So, why stick around?"

"I stayed, of course, Snape, because I gave my word."

"Come again?"

"Shall we go on?" asked Malfoy, his customary expression of haughty disdain returning to his pointed features. He headed for the door, but opened it much more cautiously this time.

"Slytherins may not have much of a sense of honour, Harry," said Ron, by way of explanation, "but he swore on his name. That's like…practically a binding magical contract for a pureblood."

"What is a pureblood, anyway?"

"It means that both of his parents are magical, and his parents' parents were all magical, and their parents were all magical…Malfoys are 'pure' as far back as anyone can remember. So are the Weasleys," he added, with a touch of embarrassment, "but we don't go around talking about it, we don't call Muggle-borns the m-word the way he did."

"You mean mudblood? What does that mean?"

"It's a really foul name for someone who's Muggle-born, like Hermione…don't say it, though. It's like…you know, dirty blood. Bloody Malfoy…Can't I curse him, Harry, just a little?"

"No. I promised. My mother means just as much to me as any old name does to him."

"Are you lot coming or not?" said Malfoy.