Hallucinations...?

Alright, this is fucking creepy. I was walking upstairs to my bedroom, and as I was going up, I saw some shadow type thing at the end of the hallway. It was still there when I got to the top, but I could see what it actually was. It was a guy, but he was... I can't find one word alone to describe him. He was abnormally tall (I didn't measure him so don't ask exactly), appeared to be wearing a business suit or a tuxedo or something, and he didn't move. He was just staring at me.

But these aren't the creepiest things about him (other than the fact that he was in my fucking HOUSE). He didn't have a visible face. I was too fucking scared to move, but he eventually just... disappeared.

Now, I don't think any of it was real, I just think that whatever was in the muffin that made me sick may have also caused a hallucination of some sort. What this makes me wonder is: What kind of shit did William put in that muffin to make me see that kind of thing? Whatever it was, I just hope I don't wake up tomorrow with a craving for mushrooms.

I need to get some sleep soon, but I don't know how much I'm going to get after what I just saw. I'm off for now.

EDIT: I just realized that the guy that I kept thinking I saw out of the corner of my eye today was probably the same kind of hallucination as this one. I really need to try and get in contact with the rest of the people from the class (They all had muffins, too). They're probably dealing with this same kind of crap. If only I actually had any contact info from any of them...