The great black dog looked up at Dumbledore, then, in an instant, turned back into a man. Mrs. Weasley screamed and leapt back from the bed. “Sirius Black!” she shrieked, pointing at him. “Mum, shut up!” Ron yelled. “It’s okay!” Snape had not yelled or jumped backward, but the look on his face was one of mingled fury and horror.