Pettigrew opened his mouth and closed it several times. He seemed to have lost the ability to talk.
“Er—Mr. Black—Sirius?” said Hermione.
Black jumped at being addressed like this and stared at Hermione as though he had never seen anything quite like her.
“If you don’t mind me asking, how—how did you get out of Azkaban, if you didn’t use Dark Magic?”
“Thank you!” gasped Pettigrew, nodding frantically at her. “Exactly! Precisely what I—”
But Lupin silenced him with a look. Black was frowning slightly at Hermione, but not as though he were annoyed with her. He seemed to be pondering his answer.
“I don’t know how I did it,” he said slowly. “I think the only reason I never lost my mind is that I knew I was innocent. That wasn’t a happy thought, so the Dementors couldn’t suck it out of me… but it kept me sane and knowing who I am… helped me keep my powers… so when it all became… too much… I could transform in my cell… become a dog. Dementors can’t see, you know…” He swallowed. “They feel their way toward people by feeding off their emotions… They could tell that my feelings were less—less human, less complex when I was a dog… but they thought, of course, that I was losing my mind like everyone else in there, so it didn’t trouble them. But I was weak, very weak, and I had no hope of driving them away from me without a wand…
“But then I saw Peter in that picture… I realized he was at Hogwarts with Harry… perfectly positioned to act, if one hint reached his ears that the Dark Side was gathering strength again…”
Pettigrew was shaking his head, mouthing noiselessly, but staring all the while at Black as though hypnotized.
“…ready to strike at the moment he could be sure of allies… and to deliver the last Potter to them. If he gave them Harry, who’d dare say he’d betrayed Lord Voldemort? He’d be welcomed back with honors…
“So you see, I had to do something. I was the only one who knew Peter was still alive…”
Harry remembered what Mr. Weasley had told Mrs. Wealsey. “The guards say he’s been talking in his sleep… always the same words… ‘He’s at Hogwarts.’”
“It was as if someone had lit a fire in my head, and the Dementors couldn’t destroy it… It wasn’t a happy feeling… it was an obsession… but it gave me strength, it cleared my mind. So, one night when they opened my door to bring food, I slipped past them as a dog… It’s so much harder for them to sense animal emotions that they were confused… I was thin, very thin… thin enough to slip through the bars… I swam as a dog back to the mainland… I journeyed north and slipped into the Hogwarts grounds as a dog. I’ve been living in the forest ever since, except when I came to watch the Quidditch, of course. You fly as well as your father did, Harry…”