He sank to his knees again and cautiously sniffed at the hole. Having noticed neither an animal odor nor any hint of brimstone, he rolled a bit of gravel into it and leaned closer to listen. The gravel bounced once, a few feet below the opening, and then kept rattling its way downward, struck something metallic in passing, and finally came to rest somewhere far below. Echoes suggested an underground opening the size of a room.