It was certainly not allowed to walk around Hogwarts at night, but using your prefect perks, you decided to go around for a walk at late hours of the night.

Your peaceful walk seemed disturbed by few noises, you carefully took out your wand, approaching the noise source, just to run into Tom, your heart almost stopping since you didn't expect him to be there

"What are you doing here? You shouldn't be outside your dorm this late"