"Harry -- I think I've just understood something! I've got to go to the library!" And she sprinted away, up the stairs. " does she understand?" said Harry distractedly, still looking around, trying to tell where the voice had come from. "Loads more than I do," said Ron, shaking his head. "But why's she got to go to the library?" "Because that's what Hermione does," said Ron, shrugging. "When in doubt, go to the library."