For there was a swift whipping sound, followed by a sickening crack, that Hermione knew was a cruel back-hander to the face. Ron had given her plenty of those over the years for her to recognise the sound. But this wasn’t Ron, and that pitiful, helpless yelp wasn’t her own. She turned in time to see a carpeted staircase materialise in front of her and Harry, no more than seven or eight years old, came tumbling down it till he hit the bottom, where he lay in a tangled heap, quite still and motionless, as bruises and lumps bloomed all over his unconscious head.