“They don’t need walls and water to keep the prisoners in, not when they’re trapped inside their own heads, incapable of a single cheerful thought. Most go mad within weeks.”

“First sign of madness, talking to your own head.”

“Listeners, that brings us to the end of another Potterwatch. We don’t know when it will be possible to broadcast again, but you can be sure we shall be back. Keep twiddling those dials: the next password will be ‘Mad-Eye.’ Keep each other safe. Keep faith. Good night.”

“Oh, for heaven’s sake, Sirius, Dumbledore said no!”A bearlike black dog had appeared at Harry’s side as Harry clambered over the various trunks cluttering the hall to get to Mrs. Weasley.“Oh honestly,” said Mrs. Weasley despairingly. “Well, on your own head be it!”The great black dog gave a joyful bark and gamboled around them, snapping at pigeons, and chasing its own tail. Harry couldn’t help laughing. Sirius had been trapped inside for a very long time.”

“A Wrackspurt . . . They’re invisible. They float in through your ears and make your brain go fuzzy,” she said. “I thought I felt one zooming around in here.”

“When you were straight, evil thoughts and memories came pouring up out of the darkness inside you; buzzing black flies clinging to the insides of your skull.”

“The mind is not a book, to be opened at will and examined at leisure. Thoughts are not etched on the inside of skulls, to be perused by an invader. The mind is a complex and many-layered thing, Potter… or at least, most minds are…”