A loud snap made them all jump. Professor Lupin was breaking an enormous slab of chocolate into pieces. “Here,” he said to Harry, handing him a particularly large piece. “Eat it. It’ll help.” Harry took the chocolate but didn’t eat it. “What was that thing?” he asked Lupin. “A dementor,” said Lupin, who was now giving chocolate to everyone else. “One of the dementors of Azkaban.” Everyone stared at him. Professor Lupin crumpled up the empty chocolate wrapper and put it in his pocket. “Eat,” he repeated. “It’ll help. I need to speak to the driver, excuse me . . .