"It's a bet, then," Rhiana said, "Tell me how the killer did it or wash dishes for a month." Tanner and Jenny, age 13, nodded. "Right," Rhiana said. "It happened inside a walk-in safe with locked doors, unbroken, concrete walls, ceiling and floor, no windows or other openings. The victim was alone, killed with a big knife driven into her chest and left there. She couldn't have done it herself. She didn't carry the knife inside with her...