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

by J.K. Rowling

They reached their familiar, circular dormitory with its five four-poster beds, and Harry, looking around, felt he was home at last.

Harry, at least, felt extremely foolish, staring blankly at the crystal ball, trying to keep his mind empty when thoughts such as “This is stupid” kept drifting across

The Patronus turned. It was cantering back toward Harry across the still surface of the water. It wasn’t a horse. It wasn’t a unicorn, either. It was a stag.

“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.”