“Nearly, I think. Charley, can you see me?”
“Yes, barely. Ten meters or so will bring you to the lip, as far as I can tell. I see what you mean now, Joe. But look—if they have a different wind, there must be other openings to the surface, even though this one may be blocked; and maybe we could dig through this sand…”
“That’s why I want to have Carol check the inside and Jenny the out. It’s too bad Jenny never saw the crater as it was before, but—wait; you did, Charley. Lift the boat and get a look into that hole yourself. Stay close to Jenny—you don’t want to pick her up by her safety line. You can let down and collect her when you’ve checked the crater, unless it looks as though digging were going to be quick and easy and she wants to start in at it.”
“I doubt that it will be” came the Rimmore’s rasp. “The hole I can see now is less than half as deep as the hill looks high from outside. That’s not what I remember the rest of you saying. I have no digging tools, anyway.”
“Any luck from inside, Molly and Carol?” asked the Nethneen.
“Four holes that might be tunnel openings so far, all of them different in detail from the one we came through, none of them with any air currents, and each with different kinds of stuff growing in it” was the Shervah’s answer. “We’ll keep looking, but more for wind than for similarity. I’m beginning to guess what happened to the rope. Are you up where you can see the crater yet, Charley?”
“Just a moment. Yes. I was a little too high; this wind is increasing, or at least the visibility is getting worse. The hole is half full. Stay where you are, Jenny; I’ll bring the boat down where you can reach it. You still have your own safety line, don’t you?”
“Of course. It’s fastened at the main personnel lock. Turn a quarter left—now straight down—ten meters to the right and about three aft—another two to the right—there. I have the lock open—I’m inside—outer door is closed, and I’m flushing the local air. You can do what seems good with the boat. Is the new machine ready, Joe?”
“Yes, but I’m not quite sure what we do with it now. Carol and Molly are blocked from us. We have no high-powered excavation equipment other than ordinary explosives, which it would be unsafe to use—for all we know of the local structure, we might bring the caverns down on them. We…”
“Pardon me, Joe” came Molly’s voice. “I think there is a pretty clear line of action. Since there are winds down here—we’ve found another, much fainter current and are following it—there must be other connections with the surface. I think you’d better get back to your air-current maps, maybe concentrating on the local area more than you would have done, and see how many passages you can find with winds blowing out and with winds blowing in. At the moment, Carol and I really have no basis for a guess on whether we should go upwind or down. Back to your wind maps, little friend!”
“Which were you doing with that current that led you into a narrow passage?” asked Charley.
“Downwind. The only evidence we had at the time was that we’d come in against the wind.”
“When its path got too narrow, did you backtrack?”
“Obviously.” Carol’s voice was a trifle impatient again.
“I mean past the point where you first found the current? I got the impression you went looking right away for other winds.”
“Oh. Yes, that’s right. We don’t know where that one came from.”
“Then you have at least one more lead if the one you’re using now proves useless.”
“I suppose we do. I suspect we have several hundred. What we really need is for Joe to find an incurrent passage and flood it with something nice and smelly that we could follow to its source.”
“You’re not going to take your helmets off to smell the air.”
“I’m afraid not,” agreed Molly before Carol could counter. “Even if I risked an occasional sniff, I don’t suppose I could catch anything but ammonia—which probably doesn’t have any odor to the rest of you.”
“Actually, the idea has some merit,” Carol pointed out. “The robots can do a certain amount of gas analysis, can’t they, Joe? We might keep it in mind, if the right conditions arise. Anyway, I second Molly’s motion. Back to your maps.”
“I have a further suggestion,” said Jenny. “In addition to the normal mapping, two of us could search the area for caves leading underground. Charley could use the boat and I the new mapping robot Joe has just finished. With this storm, vision won’t be much help right around here, but we could head upwind to its edge and cover the topography in detail as it moves, following it back in this direction. We can map any promising places, and even if they seem too far from you to be very helpful yet, just getting an idea of their number and distribution should be of use.”
“Joe!” Carol snapped suddenly. “The robot just stopped!”
“What was guiding it? Did you see or hear anything change?”
“We were following another air current, as I said…” “Up- or downwind?”
“Down. It must have stopped. There’s roaring ahead—I’m not sure what’s happening…”
“The storm? You weren’t hearing that before. Maybe you’ve gotten close enough to an opening to outside…”
“It wouldn’t have been that sudden, Charley. Molly, can you see anything ahead? Use any kind of light you want—I’ll cover my eyes with the regular flare lids.”
“Nothing. The passage just goes on. But the racket is getting louder—back the way we came, Carrie! As fast as we can travel! It may not be falling rock, but I can’t think of anything else that might sound anything like it. Move this thing!”
“You mean the tunnel is collapsing?” cried Jenny.
“I don’t know. Not close enough to here for us to see, but that would explain the wind’s stopping. Get back to the big cavern, at least, Carol, and do some more checking on its wind patterns—let’s see whether the ones we found earlier still exist. If the structure of this labyrinth is changing much ...” Molly left the sentence unfinished, and none of the others tried to complete it. There were several minutes of silence. The people in the boat could think of nothing useful to do, and even Charley was afraid of distracting the fleeing couple with a badly timed question. The boat, indifferent to the wind, hovered above the rapidly filling crater where the women had vanished. Its occupants could only listen to their translators.
“Back in the big place.” Carol’s voice came at last.
“Can you still hear the falling rock, if that’s what it was?”
“No, Joe; that faded out within a few seconds. Whether we got away from it or it just stopped I don’t plan to find out. I can’t hear it, or the storm, or anything but your voices. You, Molly?”
The Human shook her head negatively, then remembered that only Carol could see her. “Nothing.”
“What next? Search this level for more tunnels?”
“I don’t think so. I say back down to the lake, or whatever it should be called, and find that passage we went along earlier. It had a wind, remember—so did the one you started into. Let’s see whether those are still blowing. I’m beginning to think we’d be best off going upwind looking for places where air currents go underground.”
“Why?”
“Well…”
“Going upwind is most likely to find your ice, isn’t it, Molly?” Jenny’s voice carried amusement.
“I hadn’t thought about ice for a couple of hours at least,” the Human replied, not even blushing. “It would be interesting to find it but wouldn’t get us out of here. Right now I’m beginning to doubt that there is any.”
“What?” This was Charley, of course. “You know the density of this planet as well as I do and have seen even more of the rock it’s made of. It can’t be all silicate—there must be hydrides.”