I worry that Draco hasn't made good on his promise. Not only has he vanished into thin air, just as before, but my entire life continues as though no exchange ever occurred in the library. I find myself caught up in the most bizarre chain of thoughts — would Draco even know where to find me, to tell me, if Snape makes up his mind? Did they send some sort of invitation that's gotten lost somewhere?

To make matters worse, more and more people are becoming aware of Salazar's Seven. Between Malfoy's position as quarterback on the football team and Vincent Crabbe's disappearance, the group quickly gain notoriety, with rumours fuelled even further by the absence and mystery of Snape's students. Irrational flares of anger lick across my skin when I overhear people giggling, sighing, that they wish they could be a part of it.

"Yeah, you'll love that. Professor Snape turns into a giant bat, and has them perform satanic rituals. It's a lot of fun!" Harry calls out, filling the gossipers' faces with dread as they quickly scarper.

He gives my shoulder a small squeeze, and I smile at him in return. My fascination has been no secret, but I still can't tell my friends about what happened between Draco and me. Partially out of embarrassment, or fear of what they might think. But also because nothing's set in stone yet. I'd feel foolish telling them for nothing to end up happening. I feel foolish enough in myself.

Right, I resign myself during Flitwick's class, two days after the deal with Malfoy. I'm going to gatecrash the next football practice, and demand to speak with Malfoy.

I continue to scribble away at my essay, eyes still heavy with sleep, not enough coffee in my system to counteract the effects. When Flitwick places a gentle hand on my shoulder, I look up in fear, worried there'll be a problem with my essay just as there was with McGonagall.

"I've just received a note. Professor Snape has requested to see you," Flitwick squeaks.

Adrenaline floods through my body. Finally! It's all I can do not to bounce out of my seat.

"Okay, I'll go after class," I whisper back.

Flitwick shakes his head. "He's asked to speak with you now."

I pack up my books, heart hammering in my chest. I can feel Ginny's eyes on me. No doubt she overheard, but I can't bring myself to meet her gaze. I sling my satchel over my shoulder, and I'm halfway to the door before I realise.

"Professor," I whisper to Flitwick, sat marking papers at his desk. "Where do I go?"

Even with Flitwick's directions, it takes me a good twenty minutes to locate Snape's office. I head down the steps of the entrance hall, and enter what could be a whole new college of its own. It's darker down here, with no natural light, and only the flickering lamps on the wall to guide me. At first I think they are real fire, but upon closer inspection see they're bulbs designed to look like flaming torches. The halls are silent but for my own footsteps, tapping along. I turn left, right, right again, just as Flitwick said, but still find myself hopelessly lost. I begin to panic, my chest tightening with each breath I take. Just as I think I need to begin knocking on doors, asking somebody for directions, I see the bust Flitwick described. A noble-looking man, roman nose and curled hair. Salazar Slytherin. And the door beside it should be the one to Snape's office.

It's even thicker and older than the door to McGonagall's. I knock firmly, but still worry, wondering how the noise could possibly carry through so much wood. My nerves almost get the best of me. I begin to wonder what on earth I was thinking, why I would do this to myself. Something about being down here, so far removed from the rest of Hogwarts Academy, feels eerie. I wonder if it's too late to turn back.

The door opens slowly, revealing a hook-nosed man in black clothes. His dark eyes glitter dangerously as he looks me up and down, only partially revealed, still clutching the door as though debating whether to let me enter.

"Hello," I say, but it comes out as a squeak. "Professor Snape?"

"Come in," he says slowly, pausing between each word, opening the door further.

I scurry inside. The room looks like it was carved directly out of the earth, the walls and ceiling still natural black stone, like a cave. Various bottles and vases clutter the shelves along each wall, countless books and texts, a few portraits and diagrams. I realise quickly this is not Snape's office, but a classroom. And we are not alone.

Six other students are sat at the rows of desks. I notice Draco immediately, but he gives no indication that he's ever met me before at all, his eyes fixed firmly on the wall behind me. Something about him looks different, older. Pansy raises an eyebrow, her eyes roaming me, weighing me up. Blaise mutters something darkly to the person sat next to him. They all wear black with hints of green, crisp white shirts with blazers; turtlenecks. Too quickly, I realise I'm still in my shabby Ravenclaw blue. Sticking out like a sore thumb.

"Take a seat," Snape says, his voice still deep and slow.

I sit at the front, as far away from anyone else as I can manage. I try not to blush as I place my bag on the floor. Is this some sort of group interview situation?

"You will be transferred to Slytherin house, effective immediately. When we are finished here today, you will pack up your things, and move them to your new dorm." Snape stands motionless as he speaks, only his lips moving, only his eyes staring at me with something resembling dislike. "If you think you are here because you are clever, or special, or that it has been in any way due to your own actions, you are sorely mistaken. You are here because the Greengrass legacy has, historically, been tied to Salazar's group of Seven throughout the ages. Until, that is, a handful of generations ago, when your family decided education was of lesser importance than social climbing." His lip curls. "I am not Professor Flitwick. I am not going to coddle you, or hold your hand, or be kind enough to tell you how precious you think you are. If you have an issue with that, you will leave my classroom and never return. I have no patience for time wasters or cry-babies."

"Okay," I whisper.

"I expect at least a ninety percent pass rate from my students. If you slip below this threshold, you are gone." He begins to slowly pace now, his head snapping back towards me. "You are a… scholarship student," he sneers. "Is that correct?"

Snickers erupt from behind me. My face flushes red.

"Yes," I reply. "Just like Draco."

Somebody ooh's, and I hear Draco's voice muttering darkly.

"The difference between Mr Malfoy and yourself is that he has proven his worth. You have not. And before you attempt to vilify the very student that seconded your admittance to my class, the only reason I ask is to inform you that each of my students receives an allowance. Use it," he snarls, "to ensure your comfortable unemployment. Unless, that is, you wish to continue working as a janitor for the school, and you wish for your work to continue to suffer as a result."

"Fine," I say, my teeth clenched.

Snape continues to speak. "While you are with me, you will be exposed to occurrences that many would deem… Unnatural. And while it would be unethical," he emphasises the word, "for me to restrict your contact with students outside of this classroom, there are certain matters you will be expected to hold in confidence. These matters will directly touch your life; shape it, mould it, become it. Much like an official of our government's intelligence branch, you will inevitably need to lie. To protect the others in this room, as much as yourself."

A frown twitches across my face. I wonder if I should be writing this all down, in case I forget. But I'm terrified to move, paralysed under Snape's unwavering stare.

"By the time you leave Hogwarts Academy, you will hold a degree in Business, Psychology, Architecture, Science, Languages, Literature and History. Seven subjects, taught concurrently for seven years, as has been tradition since the school was first founded. Tell me, Miss Greengrass. What do you know of Slytherin house?"

I blink. "People say it's a dead house."

Another set of snickering breaks out. Only Snape looks unamused.

"And do you base all of your knowledge on what people say?"

I flush. "I believe it can be a valuable source of information, Professor. When verified, that is."

"And have you verified such an opinion? Picked up a library book, perhaps, on one of your cleaning rounds?"

My face must be well and truly red, my ears burning from the laughter. It seems stupid now, so stupid, that for all my weeks of pining and wondering, I hadn't once though to read about Slytherin in the library.

"Slytherin house," Snape continues, "is very much alive. It has always been more selective of its students, with admittance by invitation only. It never holds more than seven students at a time. And so, rest assured, should Vincent Crabbe decide to return to our school, you will be asked to leave my class."

"What makes you think he'll return?" I ask bravely.

The atmosphere in the room transforms. Gone is any semblance of laughter at my expense. The silence is deadly, and I get the sense there is something very, very wrong.

I can do no more than squirm in my seat as Snape approaches, each step slow and drawn-out, then bends down to lean on my desk and speak to me. "If you mention Vincent Crabbe in my classroom again, you will be thrown from this Academy with so much force your body will soar across the Atlantic."

I fight not to flinch away from his gaze. "Understood, Professor."

"Professor, it's almost time," Blaise calls out from the back of the class.

Snape continues to glare at me with distaste as he withdraws. "Follow me."