Harry Potter and the Prisoner of Azkaban (Harry Potter, #3)

by J.K. Rowling

I thought we’d seen the worst when we bought two hundred copies of the Invisible Book of Invisibility — cost a fortune, and we never found them. . . .

“Well, there you have it, Severus,” said Dumbledore calmly. “Unless you are suggesting that Harry and Hermione are able to be in two places at once,

“You think the dead we have loved ever truly leave us? You think that we don’t recall them more clearly than ever in times of great trouble? Your father is alive in you, Harry, and shows himself most plainly when you have need of him. How else could you produce that particular Patronus? Prongs rode again last night.”