Choose your own Harry Potter Fanfic

I ran downstairs and to my horror I saw the cauldron bubbling evilly, almost giggling from my fear. Potions were everywhere, on the shelves, on the floor, and as I turned I saw Snape grinning.
"Now, Potter, if we are going to do this right, we'll need a few simple rules."
"O-okay." I stuttered.
"First, you will not use the potions we make anywhere but in school grounds. Second, you will not speak to anyone about my being here."
"Why?"
"Do I make myself clear, Potter?"
"Y..yes, sir." I said softly.
"So we're understood. If you do tell anyone about me being here, I will erase your memory of me coming here and you'll tell them you have no idea what they are talking about. I am going to teach you how to make an invisibility potion."
"What?!" This was absurd. Snape had not been keen on my invisibility cloak, a potion I could learn how to make so I would never run out and could sneak around any time I wanted- then again, maybe he wanted me to get caught sneaking around. He'd no doubt have a good excuse as to why he taught that potion to me. Perhaps it wasn't a potion at all. Perhaps it was something else, something he needed me to make. Something only I could make. A dozen possibilities went through my mind, and none of them were pleasant.
"I will be returning to your house tomorrow. You will set up your ingredients for-" he waved his wand and a parchment appeared, falling into his hand- "this potion. Read it over, understand it, and know that this potion can do much more than simply make you invisible if you know its powers. Do not speak of me coming to anyone, and I will make your next year in potions class be the best year you've ever had."
That wouldn't be very hard, I thought.
Just stick a knife in me and put me out of my misery in the middle of class, that'd be an improvement alright. But all I said was
"Yes, sir."
Snape smiled and left. When the door shut, I looked over the parchment. The ingredients were all foreign to me. I didn't dare make the potion myself without him there, so I could only wait for his return or let someone know of what had transpired. Dumbledore would be the best choice, but he would no doubt speak to Snape about it and that wouldn't be good. Hermione or Ron were left. Who would be less likely to blab? Perhaps both of them could be silent about it, if I got them together. Hermione might worry about me, but she would have better ideas about what this could mean. Ron wouldn't snitch, but he might not know what was going on at all.