When in Doubt...

“Harry — I think I've just understood something! 
I've got to go to the library!” 
And she sprinted away, up the stairs...

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“What 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.” 

 ― J.K. Rowling, Harry Potter and the Chamber of Secrets