"How did you know?" Hermione demanded as they sat down for breakfast, slamming her book onto the table. The action earned her several dirty looks from their housemates, and a nonchalant glance from Mayumi.
"It's a secret." Mayumi stated.
"Well-" Hermione splitters, "It's impossible for you to have predicted the future, so how did you did it? You didn't let in the troll, did you?"
"No."
"Well?"
Mayumi glanced to her around, and gestures for them to lean closer. With a mysterious look, she blinks and whispers:
"Magic."
Before Hermione could explode with rage, Mayumi scarpered.