As they had a free period, Katie, Harry, Ron and Hermione decided to go to the library to get a headstart on some of the day's homework. Hermione had been scribbling words firecly for forty minutes without speaking a single word. Ron huffed or groaned in annoyance every few seconds, and took frequent but short breaks from homework to talk to Harry or Katie.

With one final grunt, Ron slammed The Standard Book Of Spells, Grade 2 shut. To everyone's surprise, Hermione followed suit and spoke for the first time in what felt like forever.

"Who can it be, though?" she said in a quiet voice, as though continuing a conversation they had just been having. "Who'd want all the Squibs and Muggle-borns out of Hogwarts?"

"Who do we know who thinks all Muggle-borns are scum?" Ron said. Hermione looked unconvinced.

"If you're talking about Malfoy—"

Katie's head snapped up from her book at the mention of his name.

"Of course I am!" Ron proclaimed. "You heard him: 'You'll be next, Mudbloods!' Come on, you've only got to take one look at his foul, rat face to know it's him—"

"Malfoy, the heir of Slytherin?" Hermione mocked, almost laughing.

"Maybe Ron has a point, Hermione." Harry shrugged.

"Absolutely not." Katie said quickly, attracting the trio's attention. She gulped and directed her gaze to the surface of the wooden table they were sat at.

"Why not?" Ron blinked, sounding a little more aggressive than he probably intended.

"Why do you not think he's the heir of Slytherin?" Harry softened the question.

Katie shrugged and, with a hint of a blush on her cheeks, she spoke.

"I dunno... He just seems a bit too... feeble."

Ron snorted in amusement. "You got that right."

"Look at his family," Harry ignored Katie and Ron's comments. "The whole lot of them have been in Slytherin, he's always boasting about it. They could easily be Slytherin's descendants. His father's evil enough."

"They could've had the key to the Chamber of Secrets for centuries!" Ron declared. "Passing it down from father to son..."

"Well, I suppose it's possible..." Hermione agreed, cringing as she did so. Katie didn't speak a single word.

"But how do we prove it?" Harry quizzed.

Katie was one hundred percent sure that the exact same idea that crossed her mind had struck Hermione as well. The bushy-haired Gryffindor leaned across the table and spoke quietly to her friends.

"There might be a way. Of course, it would be difficult. And dangerous, very dangerous. We'd be breaking about fifty school rules, I expect."

"If, in a month or so, you feel like explaining, you will let us know, won't you?" Ron sneered.

"Polyjuice Potion." Katie said. Hermione shushed her aggresively.

"What's that?" Harry and Ron said together, their puzzled eyes glancing from one girl to the other.

"It transforms you into someone else." Hermione told them. "Think about it! We could change into three Slytherins. Malfoy wouldn't suspect a thing. He'd probably tell us anything.

"Or I, an actual Slytherin, could just ask him myself..." Katie suggested, her statement sounding more like a question.

"Does he trust you enough, though?" Hermione asked doubtfully. Now that she thought about it, Draco probably wouldn't tell Katie if he was the heir of Slytherin because she was friends with Harry, Ron and Hermione. She slumped back into her seat.

"No," she sulked. "No, he doesn't."

"Well, that settles it, then." Harry said. "Where do we find a recipe for Polyjuice Potion?"

Hermione scrunched up her face in concentration as she thought hard. "I remember Snape saying that it was in a book called Moste Potente Potions, but it's bound to be in the Restriced Section."

Hermione's friends knew well enough that, to get a book from the restricted section, you needed a signed note from a teacher.

"No teacher would be thick enough to let us take out that book, even if we told them we were just interested in the theory." Ron grumbled miserably.

"Snape will let me." Katie chimed in, once again attracting the attention of the Gryffindors.

"What?" Harry said.

Katie shrugged. "Well, he might let me. I mean, if I told him I was interested in the book for the theory, he'd probably let me get it because I'm in Slytherin, and the brighter the students in his house are, the better he'll look."

"Yes, but if we steal from his stock, he'll know it was you." Hermione countered.

Katie thought long and hard before coming to an intelligent solution to the problem at hand. "Then we'll brew it in the girl's bathroom on the first floor. No one ever goes in there. Snape won't suspect a thing."

Ron cleared his throat. "Uhm, why does no one go in there?"

"Moaning Myrtle." Katie and Hermione said in perfect sync.

"Who?"

"She's a ghost that haunts that toilet."

"She haunts a toilet?"

***

The next day, Katie slowly approached the door to Snape's office. Her heart was hammering, her knees were threatening to buckle at any moment, and her hands were shaking uncontollably. She firmly gripped the small piece of paper with the words Moste Potente Potions scribbled on it. The terrified girl had just raised her trembling fist to knock on the door when a clammer of footsteps sounded through the hall.

Katie turned her head to see Harry, Ron and Hermione thundering towards her. Hermione was waving a rather mouldy book around in the air.

"We got it!" she announced.

Realising that she in fact would not need to ask Snape for permission to get the book, relief flooded Katie and she let out a content sigh.

"How?" she asked. "Not that I'm complaining—" she then added quickly.

"Lockhart." Ron smirked. "Brainless git."

Hermione elbowed Ron hard in the side. "He is not a brainless git!"

"Come on, let's get out of here before Snape comes out." Harry said, ushering his friends away from the dingy door of their least favourite Professor's office.

Hermione led the group all the way to Moaning Myrtle's bathroom, which had an out-of-order sign stuck to the door. Disregarding the sign completely, Hermione pushed the door opened and the others followed her inside.

The bathroom was lit in a horrible green light. Moss was growing in the chipped, stone sinks, small weeds sprouted from the plaster between the tiles, and the whole bathroom looked as though it hadn't been cleaned in years. To add to the uncomfortable feeling, someone was crying — wailing, howling — in one of the far stalls.

"That'll be Myrtle." Katie whispered to Harry and Ron. Hermione plopped down on the filthy floor, the others following suit, and opened up Most Potente Potions. She skimmed through the book before finally finding the page with the heading: 'The Polyjuice Potion.' Hermione's eyes scanned the page and she frowned.

"This is the most complicated potion I've ever seen," she said. "Lacewing flies, leeches, fluxweed and knotgrass... Well, they're easy enough, they're in the student store-cupboard, we can help ourselves. Oooh, look, powdered horn of a Bicorn — don't know where we're going to get that... Shredded skin of a Boomslang — that'll be tricky too — and of course a bit of whoever we want to change into."

Ron choked on air. "Excuse me? What d'you mean, a bit of whoever we're changing into? I'm drinking nothing with Crabbe's toenails in it!"

Katie snickered, covering her mouth with her hand, which was hidden inside the sleeve of her robe. Ron shot her a glare.

"Oh, shut up, you!" he snapped. "You're not the one drinking essence of Crabbe!"

"Bet she wouldn't mind drinking essence of Malfoy." Hermione muttered, momentarily lifting her eyebrows. The other three in the room almost fell over. This was the first time that any of them had made an inappropriate joke in the presence of each other, and for it to come from Hermione—

Katie went ghastly white when what Hermione had actually said sunk in, all the while her cheeks and nose lit up a bright red, contrasting greatly with the planes of her face.

"Hermione!" Ron gasped, his eyes wide with shock.

Hermione chuckled. "Oh, honestly, calm down. Now, back to the point... We don't have to worry about that part yet. We add those bits in at the end."

"D'you realise how much we're going to have to steal, Hermione?" Harry piped up. "Shredded skin of a Boomslang, that's definitely not in the students' cupboard. What're we going to do, break into Snape's private stores?"

"Wasn't that the plan from the beginning?" Katie said and Ron nodded in agreement.

"I don't know if this is a good idea..." Harry continued. Hermione closed the book with a snap.

"Well, if you're going to chicken out, fine. I don't want to break the rules, you know. I think threatening Muggle-borns is far worse than brewing up a difficult potion. But if you don't want to find out if it's Malfoy I'll go straight to Madam Pince now and hand the book back in..."

"I never thought I'd see the day when you'd be making crude jokes and persuading us to break the rules," Ron said to Hermione. "All right, we'll do it. But not toenails, got it?"

"How long will it take to make, anyway?" Harry asked. Hermione's eyes squinted as she quickly done some calculations in her head.

"A month." she said finally.

"A month?" Harry gasped. "Hermione, Malfoy could have attacked half the Muggle-borns in the school by then!"

"I know," Hermione frowned. "But it's the best plan we've got."