"We..."
"We just got lost. We were at the Halloween costume party, and thought... thought we'd sneak out for a bit."
Harry cut Ron off before he could finish.
He didn't trust Snape as far as he could throw him, and there was no way he was mentioning what Hagrid had brought here, not to him.
He held up the mask in his hand.
"This is just something we made for the costume party."
"Hmph."
Snape gave a short, contemptuous snort, looked the two of them over, and after a moment of silence said,
"Get back to your dormitory. Now. Mr. Potter, Mr. Weasley, congratulations on losing Gryffindor fifty points. Fifty each."
"And understand this: you are not to come anywhere near the fourth floor again. And you are absolutely forbidden from entering that room."
He swept his robes back and put his wand away.
Harry and Ron didn't dare argue, but at the mention of another fifty points each, the despair on their faces was plain enough.
Last time McGonagall had docked them fifty each, they'd spent ages getting cold looks from the older students. Now, before those points were even back, another fifty were gone.
They were finished.
Heads down, thoroughly miserable, they trudged off.
Snape followed a few paces behind, watching the corridors carefully. He was half afraid those "Dementors" would turn up again and go after Harry.
Meanwhile, George, Fred, and the others had made their way to the library. The Marauder's Map had shown Filch out patrolling, bound to pass through the library eventually, so they'd decided to get there first and lie in wait.
They hadn't been there long when McGonagall's name appeared on the map, right outside.
"Blast it! It's McGonagall!"
George nearly jumped out of his skin, and waved frantically at Fred and the other two to get down and hide.
The library was enormous, and with the four of them tucked into a corner, there was a decent chance she'd miss them entirely.
They'd barely settled into hiding when the sound of footsteps reached their ears.
For some reason, the footsteps sounded oddly uneven.
"Expecto Patronum!"
A flash of white light.
"You foul things, get out of Hogwarts! I'll be reporting this to the Ministry!"
McGonagall's voice carried across the room.
The four of them grew even more curious. What on earth was going on? Was McGonagall actually fighting something?
An inexplicable chill swept over them.
The twins couldn't help but shiver, and another burst of white light flared. This time, the four of them hiding got a proper look.
Five enormous, Dementor-like creatures drifted above the library, dodging the light. The bookshelves nearest them had already grown a thick coating of frost.
"This is bad!"
Just as they were taking it all in, two of the creatures seemed to spot them, diving down out of the air with a cold that sank straight into the bone, leaving all four of them shaking.
"Incendio!"
"Protego!"
With the creatures nearly on top of them, the twins finally broke, snatching out their wands and firing off spells.
The two specters were driven back by the flames, then rejoined the others, all of them streaming into the library walls and vanishing at once. Altair had called them back.
Specters were fairly low-tier undead to begin with. They looked frightening enough, but only because they were borrowing a Dementor's reputation.
A little longer, and they'd have actually been finished off.
Seeing the creatures gone, the group let out a breath of relief.
Then their whole bodies went rigid again.
McGonagall's wand was lit, pointed straight at them.
"George?"
She'd recognized their voices, but the four clouds of black mist in front of her gave her pause. After what she'd just been through, anyone would be suspicious at the sight of four more monstrous shapes.
"Professor McGonagall..."
Caught red handed, George and the others gave up any thought of resistance. There was no running now anyway, not with her wand aimed straight at them.
All four pulled off their masks at once, back to themselves.
"George! Fred! David! Jordan!"
McGonagall lowered her wand, though her face was thunderous.
"The four of you! What on earth are you doing dressed like that, wandering around the library? Have you forgotten the school's rule against nighttime wandering entirely?"
She was furious, and more than a little shaken underneath it.
If she hadn't spotted those Dementor-like things when she did, George and the others could have been in real danger tonight.
"There is still danger in this castle right now. Get back to your dormitory immediately. Come to my office tomorrow. Fifty points from Gryffindor, each of you. And you will all be serving detention."
With that, she gave the library one more look, satisfied nothing else was amiss, and hurried the group along.
She had no time to deal with the Weasleys properly right now, not with those creatures still unaccounted for.
If the school really had been infiltrated by something like that, it would be a disaster beyond reckoning.
George and the others had seen enough of what had just happened to know this wasn't the moment for jokes, and went along without complaint.
Still uneasy, McGonagall walked them all the way to the eighth floor herself, where they ran into Snape, who had just finished escorting Harry back.
Learning that Snape had caught Harry and Ron only made her mood worse.
Knowing Snape, he'd certainly have docked points as well, which meant Gryffindor had lost three hundred points in a single night.
At this rate, finishing anywhere but dead last in the House Cup this year would be nothing short of a miracle.