Sixth graders Robert and Melissa love hating each other-- "You've been cruel to me all day, Robert," Melissa stormed at him. "I haven't done anything to deserve it!" "But, you're so much fun to tease! I can't help it!" Melissa shoved him. "I hate you!" Robert fell backward. The tunnel wall was made of old, rotted timbers. It gave way. Robert struggled not to fall by grabbing the wall. Large chunks of wood came away in his hands. Robert turned wide, surprised eyes on the wood. When he looked up, ...