"It’s fine." There’s too much panic here to mean anything. "Focus on Severus Snape, on his classroom, on the heat of a dozen boiling cauldrons and on the scent of moonstone on your preparatory slate." Slowly, stuttering memories float towards him and he smiles. "Yes, very good. Picture your very first Potions class at Hogwarts. How excited you were. Severus’s speech of "how to bottle fame, brew glory, and even put a stopper in death’."