_In the Labyrinth_ Spent and shaken, the three passed onward into the cave. Harkness searched his pockets for his neolite flash; found it--a tiny pencil with a tip of glass--and the darkness of the inner cave was flooded with light. A box of food tablets was in a pocket of Chet's jacket, and there was water that trickled in a tiny stream out of the rocks. It could have been worse, Diane pointed out with forced gaiety. But Harkness, who had gone back for a final look at the entrance to the cave, found it difficult t…