“It’s — it’s true?” faltered Professor McGonagall. “After all he’s done… all the people he’s killed… he couldn’t kill a little boy? It’s just astounding… of all the things to stop him… but how in the name of heaven did Harry survive?”
“We can only guess.” said Dumbledore. “We may never know.”
Professor McGonagall pulled out a lace handkerchief and dabbed at her eyes beneath her spectacles. Dumbledore gave a great sniff as he took a golden watch from his pocket and examined it. It was a very odd watch. It had twelve hands but no numbers; instead, little planets were moving around the edge. It must have made sense to Dumbledore, though, because he put it back in his pocket and said, “Hagrid’s late. I suppose it was he who told you I’d be here, by the way?”
“Yes,” said Professor McGonagall. “And I don’t suppose you’re going to tell me why you’re here, of all places?”
“I’ve come to bring Harry to his aunt and uncle. They’re the only family he has left now.”
“You don’t mean – you can’t mean the people who live here?” cried Professor McGonagall, jumping to her feet and pointing at number four. “Dumbledore — you can’t. I’ve been watching them all day. You couldn’t find two people who are less like us. And they’ve got this son — I saw him kicking his mother all the way up the street, screaming for sweets. Harry Potter come and live here!”
(Harry Potter and the Sorcerer's Stone)
What does the highlighted part mean?