“Alex!” She stopped so suddenly he collided with her. “Look up! Up and to the right. What do you see?”

“I see… Yes. There’s an opening all right. But how do you figure… ?”

She waved aside his objections. It felt right. Her internal compass, her ever-nervous, never-satisfied sense of direction… called her that way. She suppressed a voice of doubt, one that said she was grasping at straws. “Let’s give it a try, okay? Shall I give you a boost up? Or want I should go first?”

Alex sighed, as if to say, What have we got to lose?

“Maybe I’d better go, Teresa. That way, if it looks like a true passage, I can reach down and lift you.”

She nodded in agreement and bent over, lacing her fingers to form a step. Gently, he took her waist and turned her around. “There, that’s better. Are you ready then?” He planted one foot in her hands.

“Ready? You kidding?” she asked as she braced to take his weight. “I’m ready for anything.”

Even after they had traveled quite some distance along the steep, twisty new path, half crawling, half slithering up slanted chimneys and narrow crevices, Teresa kept refusing his offer to share the goggles. He was doing fine as leader, and she used the excuse that they couldn’t risk a transfer in all this chaos. To drop them would be a catastrophe; they might slide or tumble out of sight and never be found again.

But in truth, Teresa felt a queer craving for sightlessness right now. It was strange — difficult to explain even to herself. Why should anyone prefer to stumble along, hands waving, groping in the dark, utterly dependent on another for warning about what low overhang might lay only centimeters from her forehead? What precipice yawned beneath her feet?

And yet, twice she stopped Alex from taking a route that must have seemed reasonable by sight — the wider or flatter or easier path — urging him instead to take a lesser route. They were climbing most of the time, and though Teresa knew that was no guarantee against some dead end just around the next corner, at least upward meant they had only a mountain to contend with, not an entire planet, twelve thousand kilometers across.

This can’t be George Hutton’s route anymore, she knew after a while. There couldn’t have been this many diversions, this many narrow, twisty crawlways indicated on the map they’d lost. Alex certainly realized it as well, but said nothing. Both of them knew they’d never remember how to retrace their steps. The easy banter of an hour ago (or was it four hours? six? fourteen?) gave way to clipped, hoarse whispers as they saved their strength and tried not to think about their growing thirst.

They were blazing their own path now… going places no caver must have ever seen before. Teresa didn’t see them even now of course, but that didn’t matter. The textures were new with every turn. Under her fingertips she became familiar with many different types of rock, without associated names or images to spoil the perfect reality. Substance unsullied by metaphor.

Alex made the tactical decisions, step by step, meter by meter, small-scale choices of how to move each foot, each knee and hand. “Watch your head,” he told her. “Bend a bit more. Turn left now. Reach up and to the left. Higher. That’s it.”

Not once was there any implied rebuke in his voice, for her having led them this way… a blind woman pointing vaguely heavenward one moment, the other way the next, quite possibly taking them in circles. I’m supposed to be scientific. A trained engineer. What am I doing then, trusting both our lives to hunches?

Teresa quashed the misgivings. True enough, logic and reason were paramount. They were wiser ways by far than the old witchcraft and impulsiveness that used to guide human affairs. But reason and logic also had their limits, such as when they had no data at all to work on. Or when the data were the sort no engineer could grapple with.

We have many skills, she thought during one rest period, as Alex shared the last crumbs of protein bar and then let her lick the wrapper with her dry tongue. Some are skills we hardly ever use.

If only water-finding were one of hers. Occasionally they heard what could only be the plinking drip of liquid, somewhere beyond the beam of Alex’s goggles — often resonating tantalizingly beyond some rocky wall. Pressing your ear against a smooth surface, you could sometimes even pick up the distant roar and gurgle of the river, or perhaps another one that coursed and threaded these hidden countries below ground.

Sometime during their next stretch, she heard Alex gasp, backing up from what he described as a “bottomless pit.” Teresa remained calm as he guided her round an unseen trap that would have been their ossuary if he hadn’t spotted it in time.

They rested again on the other side. Hunger and thirst had long since become acute, and then begun fading to dull, familiar aches. But these didn’t worry Teresa as much as her growing weakness. Perhaps, a few rest stops from now, they would simply not get up again. Would their bodies then dessicate and mummify? Or was the dryness seasonal? Perhaps in a few months a slow seepage, rich in minerals, would return to these passages and gradually glue their bodies to the rocks where they sat, to seal their crypt and lapidify their bones. Or some wayward, springtime torrent might come crashing through this way, crushing and dissolving their remains, then carrying the bits all the way to distant seas.

Perhaps none of those things would have time to happen. It was still quite possible for Spivey and Hutton to lose control over the Beta singularity, in which case, even the mountain-tomb surrounding her now would prove no more solid than a house made of tissue. The distance between Teresa and her friends in the outer world seemed infinite right now, but would become academic once the taniwha reached its ravenous, final maturity, when all their atoms would rendezvous in a sudden, intimate, topological union.

Teresa wondered what that might feel like. It almost sounded attractive in a way, as she contemplated the immediate prospect of starvation. Did other lost explorers get this philosophical when they neared the end?

She wondered if Wegener in Greenland or Amundsen in the Arctic pondered the vagaries of human destiny as they, too, plodded on and on beyond all realistic hope. Perhaps that, more than cleverness, has been our secret power, Teresa thought as she and Alex got moving again, choosing yet another branching path. Even when you run out of answers, there are still possibilities to consider.

After a while though, even that consoling line of thought petered out. Tiredness settled over her like a numbing weight, thankfully dulling the ache of countless bumps and cuts and scratches. Her knee pads might have been lost some while back, or not, for she could hardly feel anything from those quarters anymore as she crawled or crouched or sidled edgewise through cramped or slanted defiles. All that remained to focus her attention was the rhythm. And an obstinacy that would not let her stop.

She had no premonition when Alex stopped suddenly. Through the hand on his arm, she felt a tremor run through his body. “Come here, Rip,” he urged in a hoarse whisper, pulling her alongside him and then over to an inclined shelf. When she was seated on the cool stone, she felt him take her head between his hands and turn it to the left, then downward a bit. “I can’t tell,” he said in a dry voice. “Is there something over there?”

Teresa blinked. By now she had gotten used to the speckles and entopic flashes the retina seems to “see” even in total darkness — the lies your eyes tell in order to pretend they still have something to do. So it took her a moment to recognize that one of those glimmers was maintaining the same vague, half-imagined, blurry outline, keeping position whichever way she tilted. Teresa gingerly bit her cracked upper lip so the pain would rouse her a bit. In a voice parched and scratchy from thirst, she asked, “Um… want to go check it out?”