High over and a little to one side of the petrol flame Dodd and Tommy had seen the slender arch of rock leading into another cleft in the rocks. They had investigated it several times, but always the fierce heat had driven them back. Both Dodd and Tommy had noticed, however, that at times the fire seemed to shrink in volume and intensity. Observation had shown them that these times were periodical, recurring about every twelve hours. "I think I've got the clue, Tommy," said Dodd, as the three watched the fiery fountain and speculated on the possibility of escape. "That flow of petrol is controlled, like the tides on earth, by the pull of the moon. Just now it is at its height. I've noticed that it loses pretty nearly half its volume at its alternating phase. If I'm right, we'll make the attempt in about twelve hours." "Bram's given us twenty-four," said Tommy. "But how about getting Haidia across?" "I go where you go," said Haidia, sidling up to Dodd and looking down upon him lovingly. "I do not afraid of the fire. If it burn me up, I go to the good place." "Where's that, Haidia?" asked Dodd. "When we die, we go to a place where it is always dark and there are no beetles, and the ground is full of shrimps. We leave our bodies behind, like the beetles, and fly about happy for ever." "Not a bad sort of place," said Dodd, squeezing Haidia's arm. "If you think you're ready to try to cross the bridge, we'll start as soon as the fire gets lower." "I'll be on the job," answered Haidia, unconsciously reproducing a phrase of Tommy's. * * * * * The girl glided away, and disappeared through the thick of the beetle crowd clustered about the entrance to the cavern. Tommy and Dodd had already discovered that it was through her ability to reproduce a certain beetle sound meaning "not good to eat" that the girl could come and go. They had once tried it on their own account, and had narrowly escaped the lashing tentacles. After that there was nothing to do but wait. Three or four hours must have passed when Bram returned from his inner cave. "Well, Dodd, have you experienced a change of heart?" he sneered. "If you knew what's in store for you, maybe you'd come to the conclusion that you've been too cocksure about the monotremes. We're slaughtering in the morning." "That so?" asked Dodd. "That's so," shouted Bram. "The beetles are beginning to emerge from the pupae, and they'll need food if they're to be kept quiet. We're rounding up about threescore of the culls--your friend Haidia will be among them. We've got some caged ichneumon flies, pretty little things only a foot long, which will sting them in certain nerve centers, rendering them powerless to move. Then we shall bury them, standing up, in the vegetable mould, for the beetles to devour alive, as soon as they come out of the shells. You'll feel pretty, Dodd, standing there unable to move, with the new born beetles biting chunks out of you."