"Up to the castle?" said Snape silkily. "I don't think we need to go that far. All I have to do is call the dementors once we get out of the Willow. They'll be very pleased to see you, Black... pleased enough to give you a little kiss, I daresay... I --"
What little color there was in Black's face left it.
"You -you've got to hear me out," he croaked. "The rat -- look at the rat --"
I failed to parse the sentence. Usually, 'what' leads an exclamatory sentence, but the sentence doesn't end with '!'. Another thing I'm not sure is what the word 'it' refers to. What kind of sentence is it? How should we understand the sentence?