Lupin released Harry and fell back against a kitchen cupboard.
“Wha’ was tha’ about?” roared Hagrid.
“I’m sorry, Harry, but I had to check,” said Lupin tersely. “We’ve been betrayed. Voldemort knew that you were being moved tonight and the only people who could have told him were directly involved in the plan. You might have been an impostor.”
“So why aren’ you checkin’ me?” panted Hagrid, still struggling with the door.
“You’re half-giant,” said Lupin, looking up at Hagrid. “The Polyjuice Potion is designed for human use only.”
“None of the Order would have told Voldemort we were moving tonight,” said Harry. The idea was dreadful to him, he could not believe it of any of them. “Voldemort only caught up with me toward the end, he didn’t know which one I was in the beginning. If he’d been in on the plan he’d have known from the start I was the one with Hagrid.”
“Voldemort caught up with you?” said Lupin sharply. “What happened? How did you escape?”
Harry explained how the Death Eaters pursuing them had seemed to recognize him as the true Harry, how they had abandoned the chase, how they must have summoned Voldemort, who had appeared just before he and Hagrid had reached the sanctuary of Tonks’s parents.
“They recognized you? But how? What had you done?”
“I…” Harry tried to remember; the whole journey seemed like a blur of panic and confusion. “I saw Stan Shunpike… You know, the bloke who was the conductor on the Knight Bus? And I tried to Disarm him instead of—well, he doesn’t know what he’s doing, does he? He must be Imperiused!”