Hume went down on one knee, examined the ground growth, gingerly lifted the lace of vertebrae forming a spine. That ended in a crushed break which he studied briefly before he laid the bones gently back into the concealing cover of the mossy stuff. "That was done by teeth!" The cup of green valley had not changed, it was the same as it had been when they had emerged from the crevice. But now every clump of trees, every wind-rippled mound of brush promised cover. Vye moistened his lips, diverted his eyes from the skull. "Weathered," Hume said slowly, "must have been here for seasons, maybe planet years." "A survivor from the L-B?" Yet this spot lay days of travel from that clearing back in the plains. "How did he get here?" "Probably the same way we would have, had we not holed up on that river island." Driven! Perhaps the lone human on Jumala herded up into this dead-end valley by the globes or the blue beasts. "This process must have been in action for some time." "Why?" "I can give you two reasons." Hume studied the nearest trees narrowly. "First--for some purpose, whatever we are up against wants all interlopers moved out of the lowlands into this section, either to imprison them, or to keep them under surveillance. Second--" He hesitated. Vye's own imagination supplied a second reason, a revolting one he tried to deny to himself even as he put it into words: "That broken spine--food...." Vye wanted Hume to contradict him, but the Hunter only glanced around, his expression already sufficient answer. "Let's get out of here!" Vye was fighting down panic with every ounce of control he could summon, trying not to bolt for the crevice. But he knew he could not force himself any farther into that sinister valley. "If we can!" Hume's words lingered direly in his ears. Stones had smashed the globes by the river. If they still waited out there Vye was willing to try and break them with his bare hands, should escape demand such action. Hume must have agreed with those thoughts, he was already taking long strides back to the cliff entrance. But that door was closed. Hume's foot, raised for the last step toward the crevice corridor, struck an invisible obstruction. He reeled back, clutching at Vye's shoulder. "Something's there!" The younger man put out his hand questingly. What his fingers flattened against was not a tight, solid surface, but rather an unseen elastic curtain which gave a little under his prodding and then drew taut again. Together they explored by touch what they could not see. The crevice through which they had entered was now closed with a curtain they could not pierce or break. Hume tried his ray tube. They watched thin flame run up and down that invisible barrier, but not destroy it. Hume relooped the tube. "Their trap is sprung."