"American president," Harry replied, absent-minded, "Not the point. The point is, as Hermione's said, this," he gestured around the room, "is not a secret. First, because there are already several people in the known, and second, Severus gave you a potion before you flooed over. Tom could obliviate you, and you would not remember a single thing about these holidays. We would make you think that you've gotten food poisoning. You would wake-up in the Slytherin dorm tomorrow, feeling fine, being none the wiser."