“They couldn’t keep me company as humans, so they kept me company as animals,” said Lupin. “A werewolf is only a danger to people. They sneaked out of the castle every month under James’s Invisibility Cloak. They transformed . . . Peter, as the smallest, could slip beneath the Willow’s attacking branches and touch the knot that freezes it. They would then slip down the tunnel and join me. Under their influence, I became less dangerous. My body was still wolfish, but my mind seemed to become less so while I was with them.”

“Hurry up, Remus,” snarled Black, who was still watching Scabbers with a horrible sort of hunger on his face.

“I’m getting there, Sirius, I’m getting there . . . well, highly exciting possibilities were open to us now that we could all transform. Soon we were leaving the Shrieking Shack and roaming the school grounds and the village by night. Sirius and James transformed into such large animals, they were able to keep a werewolf in check. I doubt whether any Hogwarts students ever found out more about the Hogwarts grounds and Hogsmeade than we did . . . And that’s how we came to write the Marauder’s Map, and sign it with our nicknames. Sirius is Padfoot. Peter is Wormtail. James was Prongs.”

“What sort of animal—?” Harry began, but Hermione cut him off.

“That was still really dangerous! Running around in the dark with a werewolf! What if you’d given the others the slip, and bitten somebody?”

“A thought that still haunts me,” said Lupin heavily. “And there were near misses, many of them. We laughed about them afterwards. We were young, thoughtless—carried away with our own cleverness.”

“I sometimes felt guilty about betraying Dumbledore’s trust, of course . . . he had admitted me to Hogwarts when no other headmaster would have done so, and he had no idea I was breaking the rules he had set down for my own and others’ safety. He never knew I had led three fellow students into becoming Animagi illegally. But I always managed to forget my guilty feelings every time we sat down to plan our next month’s adventure. And I haven’t changed . . .