22

Agata pressed the broom down firmly against the floor of her cabin and tried again. “How hard can it be?” she muttered. Dust starts off in a large area. Pressure is applied inward along successive portions of the border. Dust ends up in a smaller area, ready to be collected and removed. On the face of it, this didn’t even pose a conflict with the local arrow: Esilian dust should have been happy to have its entropy decreased as her own time advanced.

But as she moved the broom across the floor, duly concentrating the dust ahead of it, other dust began to appear behind it—some of it falling from the air, some sliding over the stone to pile up against the bristles. Its entropy was decreasing too, as it accumulated from whatever scattered reaches of the Surveyor in which it had been lurking. The net result was that the stretch of floor she’d swept remained as dusty as ever.

Azelio knocked on her open door. “I know you’re busy, but Ramiro’s sleeping and Tarquinia’s on watch—”

“I’m not busy,” Agata assured him. “Do you want a hand with the measurements?”

“If you don’t mind.” Azelio nodded at the broom. “Have you found the trick to it?”

“Not really,” she admitted. “Maybe what we need is some kind of covered system of barriers. If we can place it on the floor and then reconfigure it without opening the cover, we ought to able to manipulate the dust inside without any more arriving.”

“That sounds … elaborate.”

Agata put on her corset and tool belt and followed Azelio to the airlock, then waited for him to cycle through. The view through the window showed that the weather was calm, but the Surveyor had become so filthy that Tarquinia now insisted on the protocol, regardless. Agata was beginning to suspect that the only remedy for the dust invasion would be to ascend into the void and flush every room out with clean air—and even that depended on their arrow prevailing and the void not being ready with a conspiracy of pollutants poised to rush in the moment they opened the airlock, in a perfect reversal of the intended purge.

Outside, she caught up with Azelio at the start of the trail. It was Ramiro who’d noticed the regularly spaced indentations in the ground after the last high winds, and decided to fill them with rocks marking the way to each of the four test plots. Agata hadn’t questioned him too closely on the matter, but she suspected that he’d already been contemplating doing something similar. The idea hadn’t come from nowhere, inspired by nothing but the evidence of its own implementation.

“How are the calculations going?” Azelio asked her, as they started along the trail.

“Slowly.”

“Just as well. If you finish them, what will you do on the journey back?”

“There’s no risk of that.” Agata had set aside her efforts to understand the curved vacuum and instead had spent the last two stints attempting to analyze their current situation, using a crude model of a field in which two opposing thermodynamic arrows met. But in the versions that were simple enough to handle, both arrows rapidly decayed away, leading almost immediately to a time-blind equilibrium state. The reality, in which countless slender fingers of opposing time interpenetrated, seemed to depend on details too subtle for her to approximate in any meaningful way.

“It’s Luisa’s fifth birthday today,” Azelio announced cheerfully. “I’ll show you her drawing for it when we get back.”

“Happy birthday Luisa!” Agata played her coherer’s beam over the gray stones to her left. “You never peek, do you? You never riffle through the pile to see what’s coming up?”

Azelio buzzed. “Of course not! That would defeat the whole point.”

“I know. But that wouldn’t be enough to stop me.”

When they reached the first plot the plants were all dormant, their flowers closed. Agata glanced up at the sky; she knew from the positions of the stars that the sun was well above the horizon, but she would have had to forego artificial light for a few lapses to have any chance of picking out the faint disk. “I was hoping the petals might synchronize to the Esilian day,” she said. “They give out photons, the sun accepts them: what could be more sensible than that?”

“Except that eons of evolution has left them with no skill but waiting for an ordinary night, not a time-reversed day.”

“Maybe the settlers could breed it into them,” Agata suggested. If detecting the dawn for themselves was too hard, the plants could still be prodded with more conventional signals into following the new cycle. For now, the Esilian sun would be getting its due regardless—from the plants, the ground, and her own skin—but not in any useful way.

“Can you do the heights and the stalk circumferences?” Azelio asked her.

“Sure.” Agata knelt by the first plant and reached into her tool belt. In a perfect world some clever instrument builder would have added a data recorder directly to the tape measure, but instead she had to aim her coherer so she could read the tape by eye, raise the figure on her skin, and have her corset record it. “Is one soil type racing ahead yet?” she asked Azelio. He’d started from the other end of the row, making his own inspection to record the number and condition of the flowers.

“No.”

“So there’s not much difference? The settlers could farm anywhere?”

Azelio was silent. Agata regretted distracting him; she’d probably made him lose count.

As he stood to move on to the next plant, he said, “Actually, they’ve all stopped growing.”

Agata was startled; nothing in Azelio’s demeanor had prepared her for this news. “All of them? Every single one?”

“Yes.” Azelio spoke calmly. “At first it was only a few cases, and I put it down to transplantation shock. But the numbers just kept getting worse, and three days ago the last exceptions succumbed.”

Agata struggled to find the least dismaying interpretation of these facts. “Do you think it’s the wind?” They could always improve the wind breaks, or even relocate the whole experiment.

“No. They haven’t lost that many petals, or had roots dislodged.”

“So it’s the soil,” she concluded. “All four kinds are inhospitable.”

“It’s looking that way.”

“Have you told Ramiro?”

“The trial isn’t finished yet,” Azelio stressed. “There’s still a chance that this could be a temporary hiatus.”

“Right.” Agata understood now why he’d called on her to help him with the measurements: he was trying to keep the results from Ramiro for as long as possible, in the hope that something would change.

Azelio knelt down and continued his inspection; Agata did the same. As she turned the revelation over in her mind, she was surprised at her own equanimity. After six years away from the mountain the conflict they’d come here to remedy seemed remote and petty. If they really could rid the Peerless of Medoro’s killers by showing that a settlement was viable, she’d certainly relish that victory—but between the light deflection measurements and her work on the vacuum, she already found it impossible to think of her time here as wasted.

But Azelio had no such consolations; he was only here in the hope of making the mountain safer for the children he’d promised to protect.

On their way to the next plot Agata asked him, “Is it the composition of the soil? Or is it the arrow?”

“I can’t say for sure,” Azelio replied.

“Can’t you guess?” Agata pressed him.

He said, “The spectra suggest that at least two of the soil types should have had everything the wheat needed.”

“So it probably is the arrow?” There was nothing inimical to life about the mere presence of a conflicting arrow; the crew had survived it perfectly well, thanks to their store of food with its unambiguous origins and their undiminished ability to rid their bodies of excess heat. Esilio even accepted their excrement without complaint, however bizarre the material’s fate would seem to a time-reversed observer. But the plants’ uptake of nutrients relied on interactions between their roots and the native soil at a microscopic level, and there was no guarantee that the two systems, left to themselves, would simply sort out their differences.

Azelio wasn’t ready to give up hope of a simple agronomic solution. “We could try mixing the most promising soils,” he said. “Or we could look for better conditions elsewhere. If it’s the arrow, that’s the end of it.”

Agata said, “I’ll defer to your expertise on soil chemistry—but when it comes to the arrow, let me be the judge. The problem still might not be insurmountable.”

“Really?” Azelio buzzed skeptically. “You can’t even sweep your own floor any more. How are you going to reach into the ground and persuade every speck of dust that it’s mistaken about the route it’s taking away from the entropy minimum?”

Agata had no answer to that. But if she couldn’t change the brute facts, the cosmos wasn’t taking sides in this clash: it simply had no choice but to reconcile everything it had brought together. If there had to be an accommodation between Esilio’s arrow and the Surveyor’s, the trick would be to find a way to make the crop’s failure even more improbable than its success.

Ramiro must have made a choice, Agata realized, not to seek constant updates on the state of the crops. Warned that there could be problems at the start as the plants adapted to their new conditions, he’d stepped back and left it to Azelio to monitor their health, and to offer a verdict only once it was warranted.

But Ramiro wasn’t blind, and as the flowers ceased unfurling and the stalks began to wither, Agata could see that both men were losing hope.

Bell after bell, day after day, she sketched elaborate diagrams for machines to manipulate the soil’s properties. Chemically, each mineral grain was no different from that of an equivalent on the Peerless or the home world. Physically, the distinction came down to the fact that soil on the home world had once been solid rock, while for Esilian soil, from her own point of view, that fate still lay in the future. Or in Esilio’s terms, the vast bulk of the planet’s soil had been eroded from rock … leaving two competing possibilities: that some small portion of it had actually been emitted from the roots of time-reversed stalks of wheat, or that those strange withered plants had failed to contribute anything before finally regaining their health and being carried away by the visitors.

Still, a plant knew nothing of the past and future of each grain of sand; the whole interaction with the roots had to make sense in the present. If she could find a way to measure the detailed distribution of thermal vibrations in the soil they’d brought with them, and then recreate that in the native soil, it would no longer be statistically reasonable for the plants to fail to absorb it.

To the naked eye, soil was just soil—and if the differences were microscopic, how hard could they be to erase? But when she took the most promising of her schemes and thought seriously about the practicalities, the measurements were close to impossible, the manipulations impractical, the computations prohibitive and the projected throughput so slow that a cubic scant of soil would have taken eons to process.

Agata deleted the sketches from her console. She peeled off her corset and lay down on her sand bed. The whole approach was a dead end: she might as well have set out to reverse the motion of every particle of air in the Surveyor in the hope of creating a breeze that would carry all the dust away.

Anything that sought to inscribe a new arrow into the soil at a microscopic level was doomed; the numbers would always be against her. What she needed was something infinitely less subtle.

Agata waited until she had a chance to speak to Tarquinia alone. “Do you remember telling me once that you believed Greta had put a bomb on the Surveyor?”

Tarquinia replied warily, “No, but I’ll take your word for it.”

“My word that there’s a bomb?”

“No, your word that I told you.”

“So it’s true?”

Tarquinia struggled to reconstruct some half-forgotten chain of inferences. “Verano dropped some hints. He was very apologetic.”

“Is there any way to be sure?” Agata pleaded. “Greta might have put him up to the apology, as a kind of misinformation.” Even before the launch, the whole crazed-anti-messager-rams-the-Peerless scenario had never struck her as very plausible, and after spending six years with Ramiro—irritating as he could be—Agata had to strive mightily to put herself inside the head of anyone who’d imagined him commandeering the Surveyor and turning it into a weapon.

Tarquinia was bemused. “This is a strange time to start worrying about it,” she said. “If an unexpected bump could set it off, we’d have been dead long ago.”

“If the Council really didn’t trust Ramiro not to turn saboteur,” Agata reasoned, “then they wouldn’t have been content with a bluff, would they? They would have insisted on some genuine means to destroy the Surveyor if it turned rogue.”

“I suppose that’s true,” Tarquinia agreed. “Though over the last six years I’ve become pleasantly accustomed to not having to think about politicians at all, so I don’t know what my judgment is worth now.”

“If there’s a bomb, we need to find it,” Agata declared. “We need to cut it open and extract the explosive.”

Tarquinia swiveled on her couch, assessing this suggestion. “We need to locate the hidden, possibly tamper-proof bomb that’s been obliging enough not to kill us so far, and start prodding and poking at it now … because?”

“Because the test plots are failing,” Agata explained. “So we need to take the explosive up into the hills, turn some rock into soil for our-selves—against the Esilian arrow—and see if that imbues the soil with the properties it needs to support plant growth.”

“If wheat hadn’t failed to grow properly in weightlessness,” Tarquinia mused, “then Yalda never would have ordered the spin-up. And if Yalda hadn’t ordered the spin-up, the Peerless might well have been incinerated by antimatter. So really, I ought to be encouraged by history: anything that starts with crop failure ends well.” There was a sound of hardstone scraping against hardstone, then slipping.

“Can you see what you’re doing?” Agata aimed her own coherer down into the maintenance shaft.

“Yes, I can see,” Tarquinia replied. “It’s just that none of these bolts have been turned since the engines were assembled.”

“The bomb’s not going to explode just because you open that panel, is it?” Agata asked anxiously.

Tarquinia looked up at her, affronted. “However much pressure he was under, Verano would never have done anything so perverse. We’re entitled to inspect our own engines; that hardly amounts to an act of sedition.”

There was a long silence, followed by a rhythmic squeaking noise that was almost certainly one of the bolts being turned. Agata restrained herself from cheering; Ramiro was asleep.

It took Tarquinia more than a chime to loosen all six bolts and remove the access panel. Agata peered over her shoulder into the exposed cavity, where cooling pipes ran along the back of the rebounders. If one of the banks of rebounders had failed, someone could have squeezed in here to fit a replacement.

“Anything?” Agata asked hopefully.

“Nothing obvious,” Tarquinia admitted. “I thought this was the last place we hadn’t poked around in, but maybe I should sit down with the maintenance logs to confirm that.”

“Right.”

Tarquinia lingered, lowering her head part-way through the hatch and turning her face sideways. “There’s a big stone beam that goes right across the top of the engines, from rim to rim.”

“Could something be attached to it?” Agata suggested. “Out of sight from where you are?”

“I’m just wondering why it’s there at all,” Tarquinia replied. “The floors of the cabins should provide enough bracing for the engines. And why a beam that runs across one particular diameter of the disk, and not another one at right angles to it? Nothing about the stress from the engines picks out one axis like that.”

“No.”

Tarquinia said, “If I don’t come out in six lapses, send in Azelio with a rope.”

“Azelio?”

“No offense to you or Ramiro, but he’s the skinniest. There’s not much point in two people getting stuck.” Tarquinia climbed head first through the access hatch, slithering deeper and humming softly as the cooling pipes banged against her, until even her feet had disappeared from view.

Agata waited, listening intently for any cries of discovery or distress. She was starting to wonder if she should have kept her inspiration to herself. Tarquinia trapped in the guts of the Surveyor would not be a happy outcome—and if she actually located the mythical device there could be worse to follow.

Worrying silences were punctuated with thuds, pings and echoing curses. Finally, Agata heard Tarquinia returning, her steady advance eliciting a resonant hum from the maze of pipes.

“That was exhausting,” she said. “Can you give me a hand up?”

Agata jumped down into the shaft and helped her out through the hatch. The flesh of Tarquinia’s torso had become corrugated as she’d forced it between the pipes, giving her the appearance of a decoratively shaped novelty loaf on legs.

“Any luck?”

Tarquinia said, “There’s nothing hidden beside the beam.”

“Oh.”

“But the beam itself is hollow.”

“Really? How can you tell?”

“You can hear it when you tap,” Tarquinia explained.

“Couldn’t that just be to save mass?”

“In principle it could be. But when I got to the far end I found something peculiar: it looks as if the cooling air is actually routed through the beam. Why do that, except to make life harder on anyone tampering with it?”

“So if there’s a bomb,” Agata said, “it might be anywhere inside a hardstone beam that spans the diameter of the Surveyor. And the only way we’ll ever know for sure is if we cut the whole thing open—in a place where there’s barely room to move, let alone the space to wield tools safely.”

Tarquinia inclined her head admiringly. “Trust Verano to find a civilized solution.”

Agata hummed with distaste. “Is there such a thing as a civilized bomb?”

“Well, no,” Tarquinia conceded. “But the Council would have asked him to fit a booby trap, and at least he made that idea redundant. There’s no way that Ramiro alone—or even the four of us—could have taken that hiding place apart and left the Surveyor functioning. A booby-trapped bomb would probably have been triggered by accident, long ago. We can thank Verano for finding a way to make the thing as good as tamper-proof, without turning it into a death sentence.”

Agata said, “I’ll send him flowers when I get back. But if we can’t get the bomb out and leave the Surveyor functioning—”

“We couldn’t have done it in the void,” Tarquinia interjected. “But with an external atmosphere, there’s no comparison. I think even the most paranoid Councilor would have reasoned that if Ramiro had proposed the mission merely as a cover for an attack on the Peerless, he would hardly have been willing to spend twelve years actually detouring all the way to Esilio just to remove this thing.”

“You really think you can go back down there and slice the beam open?” Agata gestured at the curves still imprinted into Tarquinia’s body.

Tarquinia said, “Not just like that. First we take out most of the cooling pipes. Then we drill inspection holes in the beam, to see what we can see. The whole exercise could take a while, but it’s not impossible.”

“Assuming there are no other problems. Assuming there really is no booby trap.”

Tarquinia said, “Yes.”

Agata slumped against the side of the shaft. Before she’d approached Tarquinia, she’d been picturing the bomb hidden behind a false wall at the back of the pantry, requiring nothing more to disarm it than the snip of a cable.

Tarquinia began smoothing out the kinks in her flesh. “I’m not going to try something like this without unanimous assent. And just because you raised the idea yourself doesn’t mean you can’t change your mind.”

As Agata described her plan to blast their own arrow into the Esilian soil, she could see an expression of delight growing on Azelio’s face—as if she’d slipped a drawing of a flourishing garden sprouting from a bomb-shattered hillside into the stack the children had left him. There was skepticism too, but she was sure now that he would understand that it was at least worth trying.

Ramiro, though, remained as dispirited as ever. “If we do set off this explosive,” he reasoned, “shouldn’t we be able to see some evidence of that already?”

Agata said, “You mean a crater?”

“Yes.”

“If we found a site like that, it would be useless to us. It would imply that after we set off the bomb, the crater would be gone and the sand around it would be rock again.”

Ramiro scowled. “Esilio doesn’t care what’s useful or useless, or it wouldn’t have killed the plants, would it?”

“Esilio doesn’t care,” Agata agreed, “but why would we go ahead and set off the bomb there, knowing that it would do us no good?”

“Because the crater would prove that we did!” Ramiro replied heatedly.

“But as far as we know, there is no such crater.” Agata met his gaze openly, trying to reassure him of her sincerity: she wasn’t playing some verbal game just to annoy him. “There is no crater, because if we saw it, we wouldn’t choose to make it. Esilio can’t force our hand; whatever happens has to be consistent with everything, including our motives.”

Ramiro said, “It can’t force our hand, but there could still be an accident.”

“That’s true. But if we saw such a crater, we wouldn’t even go near it with the explosive.” Agata would have liked to have taken comfort from the fact that there were no signs at the landing site of any future accident, but if the blast was capable of imposing its own arrow that meant nothing.

Ramiro’s hostility wavered. “I don’t know how to think about any of this,” he admitted. He ran a hand over his face. “If the plants can’t bring their arrow to Esilio, why should a bomb do any better?”

“The roots of a plant aren’t entirely passive,” Azelio replied, “but they do rely on the state of the soil. I don’t think the bomb going off will rely on anything like that.”

“But in Esilian time,” Ramiro protested, “all the soil we’re supposedly going to make with this bomb has to mesh perfectly with a backward explosion in such a way that it forms a solid rock. How likely is that?”

“How likely are the alternatives?” Agata countered. “How likely is it that the explosive will fail to detonate? How likely is it that we’ll allow it explode in an existing crater instead—just to pander to Esilio’s arrow?”

“Don’t ask me,” Ramiro replied bitterly. “I only live here.” Tarquinia reached over and squeezed his shoulder.

Agata said, “I can’t predict anything with certainty either, but surely it’s worth doing the experiment.”

Azelio turned to Tarquinia. “You think you can extract the explosive safely?”

Tarquinia phrased her reply carefully. “I’m as sure as I can be that Verano wouldn’t have allowed anything on the Surveyor that could kill us from a bump or a broken connection. Whether I manage to set it off anyway is another question.”

They spent three more chimes talking over the details, then Tarquinia called for a vote.

Ramiro’s gloom had given Agata pause. Even if the plan succeeded, he might well end up back on the Peerless warning his fellow anti-messagers that the crops counted for nothing when Esilio itself would rot their minds. Why should she risk her life if it would make no difference to the fate of the mountain?

Azelio said, “I’m for it.”

Tarquinia followed him quickly. “I am too.”

Ramiro was silent. Agata willed him to mutter a surly veto, sparing her the need to make a decision, but having advertised his confusion already he kept his resolve much longer than she could.

“I’m for it,” she said, unsure now if she had any better reason than her wish to see Azelio hopeful again.

Ramiro stared at the floor. Agata felt a twinge of sympathy for him: he’d come here with nothing but good intentions, hoping to grant both of the warring parties a chance to live exactly as they wished. It was not his fault that Esilio wasn’t so accommodating.

“I’m for it,” he said finally. “If we balk at the risk we could still get killed by a Hurtler on the way back—but we can’t go back without trying everything. If people can survive here, they need to know.”

Tarquinia said, “Right.”

As she rose from her couch Ramiro added, “To be honest, though, there’s a better reason to do this than anything it can tell us about the crops.”

Agata was confused. “What’s that?”

Ramiro said, “The look on Greta’s face when we tell her exactly what we did with her beautiful bomb.”

Agata sat in the tent, wearing her helmet so she could hear the audio link clearly over the noise of the wind. Every chime or so the footfalls and gentle clanking echoing in the empty engine cavity gave way to the bone-shaking whine of hardstone being drilled. Tarquinia was making holes in the beam, hunting for the bomb.

Agata pictured the scene as she’d left it, with mirrors angled into the cavity to bring in as much Esilian sunlight as possible. But even the safety lights in the cabin above would be off now, leaving Tarquinia to work with nothing but the view through the time-reversed camera. Exposing the bomb to ordinary light might trigger a tamper-prevention device, but it wouldn’t have made much sense to include the means to detect time-reversed light, when any act of sabotage had been expected to take place close to the Peerless, where the only source would have been distant starlight.

The camera could amplify the faint image obtained by a periscope inserted in each inspection hole, with sunlight introduced by a second mirrored tube. But so far, all Tarquinia had been able to report was that there were dozens of baffles inside the hollow beam, blocking the view along its length, leaving her with no way to proceed but trial and error.

Ramiro lay on the floor of the tent, one arm covering his faceplate; Azelio was crouched beside him, his head bowed in thought. They had spent eight days stripping as much as they could out of the Surveyor, preparing themselves for the grim contingency that an explosion might leave the hull damaged but not entirely beyond repair. Tools and medical supplies filled the tent; its three neighbors held the rebounder panels, parts of the cooling and navigation systems, and their entire stock of food. Agata understood now why there’d been so much dust around in the preceding days.

“I’ve found it,” Tarquinia announced calmly. “Six strides from the rim of the hull.”

Ramiro sat up. “What is there, exactly?”

“About what you’d expect,” Tarquinia replied. “A UV receiver on a board with a photonic processor. And a cable leading from the processor into the explosive.” Agata felt sick. She could see the blue dust that had filled Medoro’s workshop; she could picture it spilling from the broken hull to mix with the Esilian soil.

“No other components on the board?” Ramiro pressed her.

Tarquinia said, “Remember when we shot up into a high orbit, to maintain contact with the probe? If that didn’t set this thing off, nothing will. There’s no accelerometer here.”

“Is the beam warm?” Ramiro asked.

Tarquinia buzzed curtly. “Yes! I just drilled a hole in it.”

“You should leave it for a chime and see if it cools down completely,” Ramiro pleaded. Agata understood his logic: a passive system that needed an external signal to wake it would not be generating heat, but the kind of photonics required to detect an incision in the cable would have to be constantly active.

“If it gave out a heat signature that would defeat the whole point of trying to hide it,” Tarquinia replied.

Ramiro said, “I think they would have imagined the cooling system still running while we were doing this.”

“All right,” Tarquinia agreed reluctantly. “I’ll wait.”

Agata caught Azelio’s eye and they exchanged grimaces of relief. Tarquinia’s unwavering conviction that Verano would have gone out of his way to make the bomb “safe” was probably justified—but impugning the man’s honor was quite low on everyone else’s list of calamities to avoid.

Ramiro took off his helmet and rubbed his eyes. “I should be doing this,” he muttered. Agata offered no opinion; in the end it had been Tarquinia’s decision.

“Is anyone hungry?” she asked. “I could go and bring some loaves.” She hadn’t seen Ramiro eat all day.

Azelio said, “I’ll go with you.”

As they unzipped the entrance to the tent a gust of wind entered, sending the walls ballooning out and loosening the stake holding down one corner; it was only the collection of heavy tools arrayed across the floor that kept it from peeling up from the ground. Ramiro went and put a foot on the wayward corner, and Agata dashed out to fix the stake. With the wind pelting her with dust the food run seemed like more trouble than it was worth; she returned to the tent.

Tarquinia’s voice came over the link. “The beam’s down to ambient temperature,” she announced. “There’s no heat coming from the bomb.”

“How’s your visibility?” Ramiro asked anxiously. They could hear the wind rising; the dust had to be obscuring the sunlight entering the Surveyor’s window.

“Good enough,” Tarquinia assured him. “I’m going to cut the cable.”

Ramiro said, “You’re tired now, and there’s not much light. Why don’t you wait for the storm to pass?”

Agata heard the drill start up again; Tarquinia would need a third hole to insert the shears.

Ramiro paced the tent. Azelio crouched in a corner, staring at the floor. The whining of the drill came to an end, replaced by a gentle scraping noise as the folded instrument was maneuvered through the hole.

“I’ve got the shears around the cable,” Tarquinia announced. Agata saw Ramiro’s faced contorted with fear. There was a soft click of the blades meeting.

The wind rose up, pelting the wall of the tent with dust. But one word came clearly through the link.

“Done.”

As Agata trudged up the rocky incline, the patch of bright ground beside the Surveyor remained visible in her rear gaze, but it looked so out of place against the dark valley floor that a part of her mind began to discount it, treating it as nothing but a flaw in her vision. The first few times she felt it vanish from her mental map of her surroundings she panicked, scanning the view for the comforting beacon until it snapped back into focus, acknowledged again as real. But after a while she stopped worrying and let it fade into the landscape. Tarquinia and Ramiro were not going to turn out the lights and hide from her. When the time came she’d have no trouble finding her way back.

Ahead, above the gray hills, the sky could not have marked the way more clearly. The direction along Esilio’s axis that they’d chosen to call “south” pierced the bowl of stars about a twelfth of a revolution below its bright rim, and from this valley in the southern mid-latitudes that celestial pole remained perpetually in view, with the rim twirling around it like a burning hoop and the stars in between never setting.

Azelio walked beside her, carrying two of his potted seedlings from the final dozen he’d held in reserve. He wasn’t complaining, but she could see him struggling with the weight as the slope increased.

“I’d be happy to take one,” she offered.

“Thanks, but I’d rather you had nothing to distract you from your own load,” he replied.

Agata raised the bomb effortlessly above her head. “It hardly weighs anything. And even if I drop it, it’s not going to go off.” Tarquinia had assured her that the explosive could only be triggered by a bright pulse of light at a specific wavelength, and the only means of delivering that pulse was strapped securely to her tool belt.

Azelio said, “I’m more worried that you might damage the detonator and we won’t be able to set it off at all.”

“Fair enough.”

Azelio had identified a promising outcrop in the images they’d taken from orbit—a body of rock whose spectral signature suggested that it could give rise to fertile soil. No one had objected when Agata had volunteered to accompany him to the site, but she still felt slightly guilty at having wormed her way out of the tedious business of moving everything back into the Surveyor. Blowing up a hillside would be vastly more enjoyable than reassembling cooling pipes and restocking the pantry.

“Can we rest for a bit?” Azelio suggested.

“Of course.” Agata placed the bomb gently on the ground then sat beside it, positioning her body so she’d be blocking its way if it began to slide. Azelio did the same with his plants.

“Do you think they already know how this ends, back on the Peerless?” he asked her.

“I expect so.” Unless there’d been an ongoing campaign of sabotage, it was hard to believe that the messaging system would not have been completed by now.

“In some ways that takes the sting off the separation,” Azelio mused. “If the children are already in contact with me, that’s almost like being there.”

“This from a man who voted against the system,” Agata teased him.

Azelio said, “If the vote had gone against the system then we wouldn’t have needed to be here at all.”

“Hmm.” Agata didn’t want to start arguing with him over the attribution of blame.

“So long as there’s peace, I don’t care about the system,” Azelio admitted wearily. “People can use it or ignore it as they wish. We managed not to go to war over shedding; we ought to be able to live with anything after that.”

“We ought to, and we will,” Agata declared. “The fanatics who can’t accept that will be free to leave.”

Azelio buzzed wryly. “Fanatics carrying the necessary stocks of explosive?”

“Maybe we can send all the bombs they’ll need in a separate craft,” Agata suggested. “We could bundle off a whole lot of freight to Esilio in an automated vessel at high acceleration, then let the settlers follow. It’s not an intractable problem; we’ll think of some way to do it safely.”

“Assuming this works at all.” Azelio nodded toward their own bomb.

“It has to work.” Agata searched the dark valley for the speck of light that marked the landing site. “If the soil is right and the arrow is right, the plants will grow. Nothing else would make sense.”

The rim of the star bowl was almost vertical as they came over the rise. Agata wished they could have chosen a landscape with more rock than dust from the start; it would have spared them the worst of the storms, and they could have passed the time just sitting outside gazing at this glorious celestial clock.

“There it is,” Azelio announced, pointing ahead. Agata could barely distinguish the hue of the outcrop from that of its surroundings, but she trusted Azelio. He’d studied the image of the hills for half a day as he’d plotted their route, and he had too much at stake to be careless.

The approach was downhill, but the ground was uneven and strewn with small, loose stones. As Agata advanced the stones began jostling her feet, accelerated from a span or two away by time-reversed friction before coming to a halt against her skin. She glanced at Azelio; he was struggling to keep his footing, distracted by the bizarre bombardment.

“Can you leave the plants here?” she asked. Once they’d set the charge they’d be retreating to about this point anyway.

“Good idea.” Azelio set the pots down and they continued.

When they reached the hillside Azelio switched on his coherer and played it over the pale brown rocks. “This is the target,” he confirmed. He gestured toward the center of the outcrop. “Anywhere about there should do it.”

Agata handed him the bomb and waited for him to step away to a safe distance, then she started swinging her pick into the rock face. Small chips of stone flew out from the point of impact, stinging her forearms, but the rush of power and freedom she felt at the sight of the growing excavation was more than enough to compensate. In Esilian time, the chips were rising from the ground, propelled into the air by conspiracies of time-reversed thermal diffusion, just to aid her as she rebuilt the rock. What stronger proof could there be that the cosmos had a place for her, with all her plans and choices? One day it would kill her, but until then the contract was clear: hardship and frustration and failure were all possible, but she would never be robbed of her will entirely.

She made the hole as deep as she could without widening it excessively; the idea was to confine the pressure wave within the rock as much as possible. When she stopped swinging, Azelio approached and held the bomb up against the opening. It didn’t quite fit at one corner. She set to work removing the obstruction.

On the next attempt, the bomb’s cubic housing entered the aperture without resistance. Azelio gently pushed it deeper, then Agata aimed her coherer into the hole. There were some small gaps around the edge of the housing, but she didn’t think they’d be enough to dissipate the energy of the blast.

She took the detonator from her tool belt. Ramiro had removed most of the original components and added a timer in place of the remote trigger. She started up the photonics and it ran a self-test; a short summary on the display panel reported that everything was working as expected. She plugged the detonation cable into the bomb, and tapped the switch to start the timer. The countdown showed nine lapses and falling. She rested the detonator in the mouth of the hole, then the two of them walked away.

The loose stones harassed them again as they crossed the ground, and although the mild pressure on their skin was exactly the same as if they’d merely been dislodging the things, the timing was still disconcerting. Agata imagined the settlers’ children, raised with all of these quirks of nature and entirely unconcerned by them. She could sympathize with Ramiro’s discomfort, and she’d even shared it at times, but she felt no unease at the prospect of generations of innocent descendants of the anti-messagers living out their lives beneath the stars here. They’d have more comfort and freedom than anyone on the Peerless. So long as the crops grew.

Azelio reached the plants; he squatted protectively in front of them. Agata turned to face the hillside.

“I forgot to use my stop watch,” she confessed.

Azelio hadn’t; he glanced down at his belt. “Still a bit more than two lapses.”

Agata groped preemptively for an antidote to disappointment. “If this doesn’t go off, I think we could probably smash enough rock for a test plot by hand.”

Azelio buzzed. “Not finely enough.”

“I’m serious! We could start with a pick but then mill down the rock chips—like making flour from grain.”

“If it does come to that, I’ll be reminding you that you volunteered. One lapse to go.”

Agata felt her gut clench painfully. Her body was bracing instinctively for danger, but silence would be far worse.

The hillside erupted with light. She flung an arm in front of her eyes, but with her rear gaze she saw her shadow stretched out behind her. The ground shook, and she hummed softly, remembering the blast that had taken Medoro. But this was its opposite: a force that might finally heal the mountain, as much as it could ever be healed.

A warm gust of air struck her skin, carrying dust but nothing harder or sharper. The light had died; Agata lowered her arm and waited for her eyes to adjust back to the starlight.

A great, loose mound of debris lay at the base of the hill. Azelio rose to his feet and put a hand on her shoulder; she realized that she was shivering.

“It’s all right,” he said.

“Yes.” At his touch Agata ached to feel more of his skin against her, but as an internal voice started weaving a story of the only fitting coda to this triumph, she shut off the absurd fantasy quickly, less afraid of any prospect of fission than of making a fool of herself with Azelio. “Let’s go see how it looks.”

They approached the blast site cautiously. In the planning meeting Tarquinia had raised the possibility of a delayed secondary collapse, but as they drew nearer that looked less likely: the new rock face was almost vertical, but they hadn’t created an unstable cave or overhang.

Azelio strode forward to inspect the mound. He knelt and picked up a handful of debris. “It looks fine enough,” he announced warily. “There’s some coarser grit in there as well, but that shouldn’t matter.” He turned to face Agata. “I think we’ve got a real chance.”

Hearing the hope in his voice, Agata felt the sense of fulfillment returning more strongly, but it was stripped now of any desire to follow her instincts to the end. She had all she needed: Azelio’s friendship, and the satisfaction of having played a part in this scheme. It was enough.

Azelio shone his coherer across the top of the mound. “That could feed a lot more than twelve plants,” he said gleefully. “I’m just glad we didn’t have to do it by hand.”

“Maybe the settlers will put their first farm here.” Agata chirped, delighted by an absurd thought. “Maybe there are traces of them around, already—a few marks that they’ll unmake in the rock.”

Azelio said, “If we can prove that they’re going to be here, will I still need to go ahead with the crop tests?”

“Yes—or they’d never come!”

“What if I lied and said I’d finished the tests?”

“Then we’ll find some graffiti here, cursing you as the cause of the great famine.”

“Which would shame me into doing the tests,” Azelio replied. He raised the beam of his coherer from the mound to the rock face.

“What’s that?”

“Where?” Agata couldn’t see anything.

“About three strides up. It looks like writing.”

Agata was sure he was joking, but she aimed her own coherer at the same spot, and the slanted light revealed the shadows of a host of narrow ridges. It really did look as if part of the stone had been carved away, leaving these lines in relief—on a surface that the blast had just exposed for the first time.

“This is too strange,” she said. She stepped onto the mound and walked across the fresh soil. She could feel herself leaving footprints, but unmaking some as well.

On a closer view, it was clear that Azelio was right: the lines on the rock face formed symbols. The sides of the ridges appeared softened and eroded, as if a generation’s worth of future dust storms had left their mark. But she could still make out most of the message.

“… came here from the home world,” she read. “To offer thanks and bring you … courage.”

Azelio said, “Who thanks whom for what?”

Agata had never been less discouraged; she had never felt less in need of this grace. But here it was: for Ramiro in his darkness, for Azelio and Tarquinia, for everyone back on the Peerless, for six more generations of struggling travelers yet to be born.

“It’s from the ancestors,” she said. “They’re going to come here and write this. They’re going to come here to tell us that everything we’ve done and everything we’ve been through was worth it in the end.”