I lay watching him between half-closed eyelids. "He gave me the idea." "He gave you a nasty concussion," said Hammer. "It was probably the only way to the idea," I answered. "I tell you the cat is a wizard. He did it on purpose. He's a black magician." Hammer laughed again, and went towards the door. "Then the idea must be black magic," he said. I smiled painfully, for my head was throbbing.