Harry skidded to a halt only once they reached the entrance hall, spinning to look at his three friends. ""We've got to go to Dumbledore," said Harry. "Hagrid told that stranger how to get past Fluffy, and it was either Snape or Voldemort under that cloak - it must've been easy, once he'd got Hagrid drunk. I just hope Dumbledore believes us. Firenze might back us up if Bane doesn't stop him. Where's Dumbledore's office?"

They looked around, as if hoping to see a sign pointing them in the right direction. They had never been told where Dumbledore lived, nor did they know anyone who had been sent to see him.

"We'll just have to - " Harry began, but a voice suddenly rang across the hall.

"What are you four doing inside?"

It was Professor McGonagall, carrying a large pile of books.

"We want to see Professor Dumbledore," said Hermione, rather bravely, Harry and Ron thought.

"See Professor Dumbledore?" Professor McGonagall repeated, as though this was a very fishy thing to want to do.

"Why?"

Harry swallowed - now what?

"It's sort of secret," he said, but he wished at once he hadn't, because Professor McGonagall's nostrils flared.

"Professor Dumbledore left ten minutes ago," she said coldly. "He received an urgent owl from the Ministry of Magic and flew off for London at once."

"He's gone ?" said Harry frantically. "Now?"

"Professor Dumbledore is a very great wizard, Jones, he has many demands on his time-"

"But this is important."

"Something you have to say is more important than the Ministry of Magic?"

"Look," said Harry, throwing caution to the winds, "Professor - it's about the Sorcerer's Stone-"
Whatever Professor McGonagall had expected, it wasn't that. The books she was carrying tumbled out of her arms, but she didn't pick them up.

"How do you know - ?" she spluttered.

"Professor, I think - I know - that Sn - that someone's going to try and steal the Stone. I've got to talk to Professor Dumbledore."

She eyed him with a mixture of shock and suspicion.

"Professor Dumbledore will be back tomorrow," she said finally. I don't know how you found out about the Stone, but rest assured, no one can possibly steal it, it's too well protected."

"But Professor-"

"Jones, I know what I'm talking about," she said shortly. She bent down and gathered up the fallen books. I suggest you all go back outside and enjoy the sunshine."

But they didn't.

"It's tonight," said Harry, once he was sure Professor McGonagall was out of earshot. "Snape's going through the trapdoor tonight. He's found out everything he needs, and now he's got Dumbledore out of the way. He sent that note, I bet the Ministry of Magic will get a real shock when Dumbledore turns up."

"But what can we-"

Hermione gasped. Harry, Ron and Draco wheeled round.

Snape was standing there.

"Good afternoon," he said smoothly.

They stared at him.

"You shouldn't be inside on a day like this," he said, with an odd, twisted smile.

"We were - " Harry began, without any idea what he was going to say.

"You want to be more careful," said Snape. "Hanging around like this, people will think you're up to something."
Harry flushed as he strode off in the direction of the staffroom before dragging his friends away quickly.

Out on the stone steps, Harry turned to the others.

"Right, here's what we've got to do," he whispered urgently. "One of us has got to keep an eye on Snape - wait outside the staff room and follow him if he leaves it. Hermione, you'd better do that."

"Why me?"

"It's obvious," said Ron, Draco nodding along quickly "You can pretend to be waiting for Professor Flitwick, you know." He put on a high voice, "'Oh Professor Flitwick, I'm so worried, I think I got question fourteen b wrong... '"

"Oh, shut up," said Hermione, but she agreed to go and watch out for Snape.

"And we'd better stay outside the third-floor corridor," Harry told Ron and Draco. "Come on."

But that part of the plan didn't work. No sooner had they reached the door separating Fluffy from the rest of the school than Professor McGonagall turned up again and this time, she lost her temper.

"I suppose you think you're harder to get past than a pack of enchantments!" she stormed. "Enough of this nonsense! If I hear you've come anywhere near here again, I'll take fifty points from Gryffindor! Yes, Malfoy, Weasley, from my own house!"

Harry and Ron went back to the common room, Harry had just said, "At least Hermione's on Snape's tail," when the portrait of the Fat Lady swung open and Hermione came in.

"I'm sorry, Harry!" she wailed. "Snape came out and asked me what I was doing, so I said I was waiting for Flitwick, and Snape went to get him, and I've only just got away, I don't know where Snape went."

"Well, that's it then, isn't it?" Harry said.

The other two stared at him. He was pale and his eyes were glittering.

"I'm going out of here tonight and I'm going to try and get to the Stone first."