Harry and Hermione in Deathly Hallows-Part 2

Philosophers Stone
"Harry Potter," said Harry.
"Are you really?" said Hermione. "I know all about you, of course -- I got a few extra books for background reading, and you're in Modern Magical History and The Rise and Fall of the Dark Arts and Great Wizarding Events of the Twentieth Century."
"Am I?" said Harry, feeling dazed.

But Hermione had given Harry something else to think about as he climbed back into bed.
As they jostled their way through a crowd of confused Hufflepuffs, Harry suddenly grabbed Ron's arm.
"I've just thought -- Hermione."
"What about her?"
"She doesn't know about the troll."

Hermione...