Tom sat tucked between a suit of armor and a cold brick wall, reading the book he had taken. He was on patrol for prefect duty: He had to watch the corridor along which was the entrance to the Slytherin dorms until midnight. Of course, no one was stupid enough to come down his way-- and he really didn't feel like making the effort to catch anyone, though with a little extra trouble he could find their routes. He'd save sacrificing their trust for some time when he needed a little something extra from the teachers.
It's a big balance of deeds, that's all, he mused. I let a Slytherin off, and he owes me something, even if it's just a little extra respect. If I catch him and turn him in, the school owes me something. Tonight, I don't need anything, so my Housemates are free to frivilously go off to the kitchens if they please. I have reading to do, besides.
He continued to sit, poring over the probably banned Dark Arts book Rigel had managed to smuggle in-- and he had managed to smuggle out. He was so engrossed he did not even notice when someone walked straight down his hall . . .