Harry Potter and the Chamber of Secrets
"It means," said Dumbledore, "that the Chamber of Secrets is indeed open again."
Madam Pomfrey clapped a hand to her mouth. Professor McGonagall stared at Dumbledore.
"The question is not who," said Dumbledore, his eyes on Colin. "The question is, how."
And from what Harry could see of Professor McGonagall's shadowy face, she didn't understand this any better than he did. (10.175-179)
"Dreadful thing, Dumbledore," said Malfoy lazily, taking out a long roll of parchment, "but the governors feel it's time for you to step aside. This is an Order of Suspension – you'll find all twelve signatures on it. I'm afraid we feel you're losing your touch. How many attacks have there been now? Two more this afternoon, wasn't it? At this rate, there'll be no Muggle-borns left at Hogwarts, and we all know what an awful loss that would be to the school." (14.124)
"We haven't seen [Hermione] for ages, Professor," Harry went on hurriedly, treading on Ron's foot, "and we thought we'd sneak down to the hospital wing, you know, and tell her the Mandrakes are nearly ready and, er, not to worry —"
Professor McGonagall was still staring at him, and for a moment, Harry thought she was going to explode, but when she spoke, it was in a strangely croaky voice.
"Of course," she said, and Harry, amazed, saw a tear glistening in her beady eye. "Of course, I realize that this has all been hardest on the friends of those who have been…I quite understand. Yes, Potter, of course you may visit Miss Granger. I will inform Professor Binns where you've gone. Tell Madam Pomfrey I have given my permission." (16.59-61)