Schild’s Ladder

Tchicaya was silent for a moment. She was right about the fuel, but he couldn’t accept what she was proposing.

"That’s not true," he said. "If I stay out here, I’m going to lose radio contact, eventually. From sheer distance in the long run, but if the border has taken on a complicated shape, I might lose my line of sight much sooner."

"Then give me the key to the Left Hand. With that, and the toolkit, I can manage everything." She sighed. "Don’t be precious about this. I don’t like the idea of leaving you to drift away, but there are more important things at stake here. The time and the fuel I used fetching you could make all the difference to the far side."

Tchicaya felt a flicker of temptation. He could wash his hands of everthing, and wake beside Rasmah on Pfaff. Mariama was being perfectly logical; time was against them, and apart from the secondhand skills that he could easily sign over to her, he was superfluous.

He wanted to trust her. Hadn’t she earned that? They’d had no end of differences, but she had always been honest with him. It seemed petty and mean-spirited to keep on doubting her.

The trouble was, he didn’t trust his own motives. Thinking the best of her would be the perfect excuse to absolve himself of all responsibility.

He said, "I’m not handing you anything. If you care so much about the far side, you’d better come and get me."

Mariama remained seated at the front of the shuttle as Tchicaya clambered out of the airlock. He nodded a greeting, and tried to smile. Her Exoself would be discouraging her from doing anything to interfere with her body’s healing, by means both gentler and more precise than a blanket of agony; extrapolating from the raw pain of the minor burns he’d willingly experienced as a child was absurd. Still, the sight of her weeping, blistered skin made his guts tighten.

He said, "Hitchhiking in space isn’t so bad. I’ve waited longer for a ride, on land."

Mariama replied through the IR link. "Try showing more flesh. That always works wonders."

On their way back to the Left Hand, Tchicaya received the first good news he’d heard since the moratorium vote. The horizon had stopped falling. The Left Hand was no longer seeing new stars creeping into view.

That in itself didn’t fix the depth of the lost region everywhere, but the particular geometry was suggestive. The new horizon was exactly where it would have been if the Planck worms had failed to penetrate the signaling layer, where the vendek population changed abruptly, a hundred kilometers into the far side.

As they approached the Left Hand, the news became even better. The fireflies had finally begun to vanish, and the timing of their deaths confirmed the best possible scenario: the border had retreated to the signaling layer, and no further.

Tchicaya was elated, but Mariama said, "Don’t assume this is the new status quo. Birago wasn’t exactly confiding in me toward the end, but if what he’s done here bears any resemblance to the work I was involved in with Tarek, the Planck worms won’t have given up at the first obstacle."

"Meaning what?"

"They’ll mutate. They’ll experiment. They’ll keep on varying themselves, until they find a way to break through."

"You knew how to do that? You had it all worked out?"

"No," she admitted. "But as soon as you showed us the vendeks themselves, they provided an awful lot of inspiration. Tarek and I didn’t pursue that, but don’t expect Birago to have passed up the opportunity."

They docked with the Left Hand, and carried it down to the point where the fireflies were disappearing.

Regaining alignment with the border took almost an hour, as a cycle of increasingly delicate adjustments brought the stylus into range. Once that was achieved, Tchicaya scribed a series of probes that would spread out laterally as well as moving straight in, improving their chances of gaining a comprehensive picture of the Planck worms. Unsurprisingly, now that the signaling layer was infected with Planck worms and exposed to vacuum, it was no longer vibrating, no longer tapping out primes. Tchicaya longed to discover the mechanism that had driven it, but he had to stay focused; trying to dissect the far-siders' ruined SETI equipment — if that was what it was — had to take second place to dealing with the plague the beacon had been unable to deter on its own.

As he launched the last probe, he turned to Mariama. "If you gave me all the details of the work you did with Tarek, there’d be no need for you to hang around."

She emitted a disgusted wheezing noise, the first real sound he’d heard her make. "Is that some kind of childish comeback, because I didn’t want to waste fuel on making you cozy?"

"No. But I’m the one who came to the Rindler to protect the far side. There’s no reason for you to keep crawling over broken glass for the sake of someone else’s agenda."

Mariama searched his face. "You really don’t trust me, do you?"

"To do what? To betray your own ideals? You always wanted to wipe this thing out."