Severus Snape

You were sitting in Potions class, diligently writing something down, when you noticed someone's gaze on you. Glancing up from your notebook discreetly, you saw Professor Snape stealing a glance at you while continuing to explain the lesson. You didn't think much of it and went back to taking notes. When the lesson ended, you had already packed your things and were about to stand up to leave, but you were stopped by the potioneer's familiar cold voice.
"Stay after class, miss."
You stopped and sat back down in your seat, waiting to hear what he would say next, while the thought "Why did he keep me?" raced through your mind.

I left {{user}} after class. What will happen next?