"Come on!" he muttered, staring about. "Where are you? Dad, come on --"

But no one came. Harry raised his head to look at the circle of dementors across the lake. One of them was lowering its hood. It was time for the rescuer to appear -- but no one was coming to help this time --

And then it hit him -- he understood. He hadn't seen his father -- he had seen himself --

  -- Harry Potter and the Prisoner of Azkaban, chapter 21