Phoresis

5

Leander was not the brightest star in the sky, but it was the brightest that ever crossed behind Tvíburi. Rosalind set up the telescope to track it, lit a lamp and prepared the comparator.

She had chosen a night when the timing would be as close to perfect as the various celestial constraints allowed. Leander needed to approach Tvíburi’s dark side, which meant the occultation had to take place well before midnight, when the sunlit portion of the twin was still skewed to the west. But then it was a question of balancing that requirement with the need to ensure that the sky was equally dark for both measurements: the one just before the occultation, and the one just before Leander set. Some of her friends had argued that it wasn’t strictly necessary to do both on the same night, but Rosalind found the idea of a prolonged delay troubling. She was confident that she could trim and fuel a lamp in such a way that it would give out constant illumination from dusk to dawn, but keeping it burning longer, let alone extinguishing and reigniting it, would be inviting inconsistency. If she ended up dead, it wasn’t going to be for a foolish reason like that.

Well before the occultation, she stopped down the light from the lamp and adjusted the comparator’s iris until the switch back and forth between starlight and lamplight induced no perceptible change in brightness. Simply staring at Leander and assigning a number to the strength of its light would have been a hopeless task, but the comparator made even the slightest difference from the reference source jump out at her. She wrote down the current size of the iris; it told her nothing on its own, but if the same setting worked again halfway to the second measurement, that would reassure her that the lamp’s output had remaining steady.

When she stepped away from the instruments to stretch her neck, she took care to shield her eyes from the light of Tvíburi, lest they lose their sensitivity. She didn’t need to watch the two bodies drawing nearer in the sky; with Joanna’s help, she’d calculated all the angles in advance and etched the landmarks she needed to be aware of into the wheel that turned the scope.

The night was cold, but there were tents around her on three sides, sparing her from the north wind. The tents hid the base of the tower, but she could see starlight glinting off the slender spike that rose up from the final tripod. She hunted for a softer, internal glow of lamplight showing through the ice, but it was late, and all her friends were probably asleep. That made her feel a little hard-done by, as if they’d owed it to her to keep a vigil, but she was the one who’d rebuffed their offers to join her on the ground for the measurements themselves. She hadn’t wanted the distraction.

Rosalind returned to the telescope, and nudged it along its preset arc until Leander was centered in the view again. She flipped to the lamp and back a few times, to reassure herself that nothing about the setup had drifted unexpectedly, but any change that had occurred was subtler than her powers of discernment. She stroked the edge of the wheel gently with her thumb, gauging the time that remained. It was strange: she’d been less anxious than this before most of her jumps, even those from untried heights. Maybe the risk here wasn’t as great as she was telling herself; if she made a mistake, one of her friends was sure to pick it up when they repeated the whole procedure. But to be complacent would still be foolish.

As she followed Leander along its path, the unlit eastern limb of Tvíburi crept into view, a bland, almost featureless gray against the deeper darkness speckled with stars. The contrast made the sister world seem closer and more quotidian than ever: it was almost as if she’d just pointed the telescope at the edge of a building, or someone was holding their hand in front of the lens. Half a dozen faint stars dimmed and disappeared behind the twin’s disk; Rosalind watched them carefully, building up a sense of the progression as it would apply to her target—trusting Joanna’s mathematics, but prepared to salvage the situation if it turned out that she’d mis-transcribed the results, or if the wheel on the scope’s mount had slipped.

The furrows on the wheel declared that the light from Leander had begun to graze the upper atmosphere of Tvíburi. Rosalind waited; she didn’t expect a visible effect until the path cut deeper.

At the halfway mark any dimming was still impossible to detect in isolation, but when she switched to the lamp and back a few times, she found she had to shrink the iris slightly before the two points of light appeared equally bright again. As Leander moved closer to the edge of the disk, she forced herself to stop trying to spot changes by anything other than the official method—but there was an unmistakable blurring of the star’s image, with the once-sharp point shimmering into a faintly trembling ellipse.

Moments before the occultation, Rosalind flicked the comparator, adjusted the iris, checked and rechecked. She had matched the lights again, perfectly, she was sure of it—and then Leander vanished from sight.

She lay back on the viewing bench, drained but elated. “Half done,” she muttered. Now all she had to do was measure the effect when the light from the same star took the longest possible path through her own world’s atmosphere—and then she’d finally know whether the most dangerous moment in her life was one she’d already lived through, or whether there was greater danger still to come.

“I’ll race you to the next level,” Joanna said, tensing her body in preparation to start bounding up the stairs.

Rosalind groaned. “Not today. If you’re bored, feel free to run ahead of me, but I just want to conserve my strength.”

“But we’re almost there!” Joanna remained beside her, keeping step with Rosalind’s measured ascent, but she was fidgeting impatiently as she spoke. “The sooner we arrive, the more daylight will be left.”

Rosalind didn’t reply; she had no intention of increasing her pace. Before a jump, she needed to be calm and unhurried. If she sprinted up the stairs, she might gain the advantage of a little more time before nightfall, but it would come at the cost of finding herself standing on the ledge feeling as if she’d been chased there.

The sun had just come out from behind Tvíburi, and it was still so high that its light had to travel obliquely through the wall of ice around them, bringing a diffuse, bluish glow to the western half of the spiral staircase. As she emerged from the shadow of the central column into the soft blue light, Rosalind contemplated the roots embedded in the ice, most visible as backlit silhouettes, but breaking through the wall in places to sprout the flowers that kept the air replenished. The Yggdrasil had served them well, but they had deceived it horribly. If she’d been alive at the time the tower was begun, she would have bet anyone that the tree would get wise and stop cooperating, long before its roots had accreted a spike of ice stretching halfway to Tvíburi.

“Can you imagine never having to climb stairs again?” Joanna asked. She made the prospect sound surreal.

“You don’t think we’ll be raising a tower of our own?” Rosalind teased her.

“Someone else can do that job.”

“Really? Who exactly are you volunteering?”

Joanna said, “The children. I’ll farm the crops, they can farm the ice.”

“Why not?” They all had their own peculiar fantasies as to how the new life would be—and there was no point cautioning anyone not to get ahead of themselves. However solid its foundations, the tower itself had only kept rising through the sheer force of its creators’ endlessly malleable hopes.

By mid-afternoon, a section of the wall had grown so bright that Rosalind was left half-blinded by its lingering afterimage each time she walked into the column’s shadow. The stairs were meant to be uniform, and she ought to have been able to climb them with her eyes closed by now, but though she knew roughly where the dozen or so mistakes were in every flight, she didn’t have the kind of flawless memory that would allow her to anticipate exactly when her ascending foot would need to land a little higher, or lower, or farther ahead. In any case, the occasional risk of a mis-step did nothing to make the journey less monotonous. The best thing about this trip was that she wouldn’t be taking the stairs back down.

“You have to promise that you won’t follow me,” she told Joanna sternly.

“I don’t even have my glider!” Joanna protested. “I’m just here for moral support.”

“I wouldn’t put it past you to have something hidden up there.”

“Only food,” Joanna replied. “But who doesn’t keep a few seeds stashed on every level?”

“What kind?” Rosalind wondered. She hadn’t eaten at all when they’d rested at noon.

“None of your business! You’re meant to be flying light!”

“A handful of seeds won’t kill me.”

“I vomited in midair once,” Joanna confessed. “It might not have been fatal, but it was certainly distracting. So don’t expect any last minute snacks from me.”

Rosalind started laughing.

“What’s so funny?” Joanna demanded.

“I’ve vomited a lot more than once.” How was it that nobody knew that the team’s most experienced flier had heaved up the contents of her stomach—however meager it was—at least as often as she’d managed to keep it down?

“At last!” Joanna pressed her hand gratefully against the sign on the wall promising the end of level thirty-six, then raced ahead and disappeared around the curve of the staircase. Rosalind felt a twinge of impatience herself, but maintained her pace; if she was going to break a leg today, she’d rather save that for a more appropriate moment.

As she stepped onto the landing, she saw Joanna waiting by the exit. “You don’t have to come out with me,” she said.

Joanna scowled. “I didn’t climb all this way to stay inside.”

Rosalind hesitated. “What happened to your stash? Have you eaten it already?”

“No, it’s…” Joanna gestured toward the connecting chambers for level thirty-seven; the pressure difference wasn’t much, but it would still take time to go through and back. “I’ll wait until you’re done here.”

“All right.” Rosalind walked over to the exit and opened the first door; when she closed it behind her she was in total darkness. She squatted down and started checking the seal, probing it with her finger from bottom to top. A speck of grit had become caught in the strip, so she opened the door again and brushed it away, then repeated the procedure.

There were six doors in total. The seals were good, but they couldn’t be perfect, and in combination they probably ended up leaking air at about the rate the root flowers were replenishing it.

Rosalind emerged from the darkness of the final chamber into dazzling sunshine. It was late afternoon, but out on the balcony the light was much stronger than down on the ground. Her skin tingled oddly in the rarefied air, and she could feel the rigid muscles closing off her windpipe, more efficiently than any of the door seals. She’d taken her last breath for a while.

She put her pack on the floor and slid the panels out, then set to work assembling her glider. Every individual panel had probably been replaced four or five times, and the bracing rods and runners even more often, but she still thought of it as the same one she’d used for her first serious jump.

Joanna stepped through the door, squinting at the sunlight. They nodded to each other, then Joanna approached and clasped her friend’s shoulder. Rosalind squeezed her hand reassuringly: this had to be done, and it would be over soon enough. But it was a cruel irony that the cost of being here meant that Joanna would be the last to know the outcome, when all their other friends were already waiting at the base of the tower to greet the returning flier.

Rosalind finished putting the glider together, then spent twice as long checking it. One of the rods felt stiff; she pulled it out and replaced it with a spare. After that, when she pushed against the frame it responded like a single object, precisely as supple and as strong as she needed it to be.

She propped the glider up against the wall of the tower, turned her back to it, and strapped herself in, securing the belt around her waist.

All this time, she’d been so far from the edge of the balcony that the ground had remained out of sight. As she walked forward, the horizon took longer than she expected to appear: it was even farther below her eye-line than the last time. She was afraid to look up at Tvíburi, to compare the angles the two worlds subtended, as if that might drive the point home far more ruthlessly. She was still a long way from the top of the tower, but some kind of dream-logic tugged at her mind, whispering that if she wasn’t careful, she might end up falling toward the wrong world.

Or rather, the right one, sooner than intended.

Rosalind turned back and raised a hand to Joanna, who reciprocated, smiling. It had taken a lot of courage for her friend to be here beside her, and a lot of strength to make it seem that it had taken none at all. Rosalind was glad that they couldn’t speak now; there were no words for a moment like this. She reached up and grasped the glider’s handle bars firmly, then turned away and walked quickly through the opening in the balcony, onto the ledge, and into the sky.

For a moment she descended almost vertically, but then the airflow grew strong enough to tip the glider, and she was facing straight down. Her body continued to harangue her for the unforgivable thing she’d just done, jangling her nerves like a terrified mother screaming at a child caught in an act of suicidal folly, even as the elation induced by the inexplicable lack of a timely impact and agonizing injuries did its best to argue its own case. Both responses were premature—and as the fall stretched on and on, with neither pain nor safety arriving to settle the argument, Rosalind’s instincts began to cede ground to her more considered judgment. Which was a cautious so far, so good.

Below her, patchy red clouds floated above the ice field. The tug of the air on the glider was still weak, and through the handle bars she could feel how little the frame was stressed. It was hard to think of that as anything negative: how kind of the atmosphere to treat her so gently. But sparing her deceleration now could only have two outcomes: a rougher ride when the deeper atmosphere fought to bring her back to terminal velocity… or an even rougher end, if it failed to slow her sufficiently before the ground completed the job.

So be it. This was what the light of Leander had demanded of her. Tvíbura’s atmosphere was much thinner than Tvíburi’s, so the fall that would demonstrate whether or not the gliders could land them safely on the twin world, if they dropped all the way from the halfway point, could start from a much lower altitude here to compensate for that disadvantage. If her measurements and calculations were correct, a jump from the top of level thirty-six would be precisely as dangerous as the crossing itself.

As Rosalind fell past the clouds, the glider began to shudder, and then roll. She shifted her weight, trying to keep it level; it wasn’t tipping very far, but it was lurching back and forth at an alarming rate. Her own skin was oblivious to the turbulence; all she could feel was a pressure and a chill that barely touched her, as if she were lying face down on a slab of ice, but wearing enough clothing to insulate her from most of its effects.

She surveyed the ground below, hunting for familiar features to note their scale and rate of growth, trying to judge her height and speed against the last jump. She spotted a jagged ravine in the ice, farther to her left than she was used to; had some chance wind pushed her to the east, or had the ground itself, whirling around the midpoint between the worlds, outpaced her own lateral velocity, diminished by altitude?

A cluster of low gray hills rose up on her right, ancient rock that must have been fresh soil a million generations ago. A patch of whorled ridges appeared in the ice below her, raked by the low sunlight. Whatever her rate of descent, it was clear now that she was traveling faster over the land than last time. That did make some sense: the glider bluntly opposed her fall, but eased the air aside as she moved forward. And if it had diverted a greater portion than usual of the energy she’d gained into horizontal motion, that might spare her some of the force of impact.

The glider’s rocking grew more violent. Rosalind could feel one of the bracing rods bowing and relaxing under the onslaught. Sustained pressure was one thing, but this repeated flexing was uncomfortably close to her own action when she was trying to snap a thick twig. She wondered if she should risk letting go of one of the handle bars in order to take hold of the threatened rod; after all, she still had the straps around her waist. But then the glider lurched suddenly, sharpening her sense of how dangerously contorted her body might end up if she left even one hand free.

She could hear the rod squeaking now, the high pitch of its complaint cutting through the noise of the wind. The thickening air buffeted the glider with a relentless, random vigor, as if trying to fold and unfold it along every possible line of weakness, never persisting with the same attack for long, but never failing to return to it later.

She coughed to open her throat and inhaled deeply, but even as she was savoring the sweetness of the air and the rush of strength to her limbs, the rod snapped, leaving its two halves dangling uselessly from their connecting points. The glider deformed, with two panels pushing inward just right of her head, then everting again under the force of the wind.

She gazed down at the shuddering blur of the ice field, trying to take comfort from its proximity even as the speed of her descent drained that consolation away. The glider’s frame was twisting, losing symmetry under its new regime, and the wind was both amplifying and exploiting the result. As the glider rolled and pitched, every sudden shift of orientation imposed its own new stresses, distorting the frame a little more.

And the angles were growing larger, the tilts more precipitous. If the glider overturned, it would break apart completely. She’d somersault with the debris for a while before it was scattered by the wind and she was left tumbling through thin air.

Rosalind tightened her left-hand grip, then reached down with her right hand and loosened the strap around her waist. As her body swung down, she reached up and snatched at the right handle bar, catching the end and then forcing her clenched fist rightward into a more secure hold.

She dangled from the handle bars, astonished equally by her own actions and the fact that they seemed to be helping. The glider was still rocking from side to side, but so long as she maintained her grip, she did not believe it would actually overbalance. Wrist straps, she thought, almost calm for a moment. The handle bars needed to be supplemented with wrist straps.

She glanced down at the ground, but struggled to interpret the faint pattern of blue-white streaks rushing by. There were no hills or ravines in sight now, and she was moving across the ice too rapidly to catch any of the finer details she was accustomed to using to gauge her height. Then she felt the sting of wind-borne dirt on her skin, and understood just how near she was.

She tucked her knees toward her head, and managed to force her feet onto the tops of the runners. The glider gleefully took the new distribution of weight as an excuse to start gyrating more wildly again, but before it could come close to overtipping, it slammed into the ice.

It bounced, twice, almost breaking her grip, spraying fine chips of ice onto her face as the runners scraped over the surface like paring knives. Rosalind kept her body rigid, certain that she alone was holding the frame together.

She tried to see where the glider was taking her, but one of the panels that had retained its position blocked her view. Abruptly, she was airborne again, tumbling, and when the glider struck the ice it was upside down. Rosalind felt an impossible tug on her right arm; she released the handle bar and let half of the glider tear itself away.

She lay still in the wreckage for a while, afraid that if she tried to move she would discover that she couldn’t. Maybe the best thing would be to rest where she was, until the shock of the impact had passed. But what if she lost consciousness?

She rose to her feet and took a few tentative steps. One of her legs had been cut, but not deeply. She felt battered, and when she flexed her right hand she knew she’d broken a finger, but her back and her limbs were intact.

Rosalind looked up across the ice and saw the tower in front of her in the distance, glinting in the late afternoon sun. She knew where she was now, and how far she had to travel. It was going to be a long walk, but there was no chance of getting lost.

As she set off, she turned back to survey the fragments of the glider strewn over the ice. She was going to have to think of the next one as new.

“I’m convinced,” she said softly. “We can survive the crossing.” She marched toward the tower, repeating the words in her mind, hoping that she’d be able to speak them with conviction by the time she reached her friends. If she’d died, they would have had to go looking for another solution, but now there was no point believing anything else.

6

As she walked through the village toward her mother’s house, Rosalind couldn’t help but feel self-conscious at how well-fed she must have looked. Not everyone she passed was alarmingly emaciated, but no one was carrying any flesh in reserve. To be ashamed of the disparity would be foolish; there’d be no point sending the expedition to Tvíburi if they all starved to death waiting for their first harvest. And if the provisions and laborers the villagers had sacrificed to the tower for the last four generations had been a heavy price to pay, she wasn’t exactly taking an easy path herself. Still, she could not recall the last time she’d really been hungry, and she doubted that was true of anyone else in sight.

When she entered the house, she saw that her mother had invited her paternal aunt, Marion, to the farewell meal, along with Marion’s daughter, Celine. Rosalind embraced them all in turn, though she’d never been close to her father’s side of the family.

They sat down at the table and began to eat.

“How quickly do you think the new villages will be established?” Marion asked. When Rosalind hesitated, she made the question more specific. “Do you think you’ll be seeing Celine there?”

“I hope so.” The older women had no expectation of reaching Tvíburi themselves. Rosalind turned to Celine. “If you ever have time, there’s no harm in practicing with a glider. If you start from low jumps, it’s not dangerous.”

“Practice, and wait for the signal,” Marion said.

Rosalind nodded. “By the time our children are old enough to help us in the fields, we should have sowed enough land for the farms to be visible through any decent telescope. Though I’ll be happier still if I’m the one who looks up, to see a new geyser sprouting from the limb of Tvíbura. In which case, migrants will still be welcome… but we won’t expect quite the same influx.”

Celine laughed, but Rosalind’s mother looked horrified. Rosalind offered her a questioning frown. Would it be better if I wished an endless famine upon the world, just to make myself less lonely?

Her mother said fervently, “Tvíburi is the future. We all know that. You’re giving us a future we’d never have otherwise.”

Rosalind was embarrassed. “I’ll do my best,” she said.

Mercifully, Celine was impervious to her aunt’s solemnity. “How many stairs are there in the tower?” she asked. “From bottom to top?”

“I don’t honestly know,” Rosalind admitted. “If I tried to calculate the total now off the top of my head, I’d probably get it wrong.”

“Don’t worry,” Celine replied. “When it’s my turn, I’ll make sure to count them, and I’ll tell you next time we meet.”

The last level of the tower was the tallest, and it had no stairs at all. Rope ladders stretched between the annular rest platforms, but though the bottoms of the platforms were helpfully painted red and the top surfaces blue, Rosalind struggled to perceive any fixed direction as up or down. She felt like an insect crawling along inside a hollowed-out tree branch, which a child had picked up and was whimsically turning this way and that. It was not that she feared being dislodged, and it seemed absurd to imagine that she could ever lose her way. But as she moved, hand over hand, in near weightlessness through the tube of luminous ice, the sense of disorientation was impossible to shake off. All she could do was embrace it, and hope she wouldn’t throw up.

“Matilda told me it was beautiful up here, but I never imagined!” Joanna called out, from a dozen rungs behind her. Matilda had worked on completing the tower, when the only thing at the open end between the ice-farmers and the void had been a series of tarpaulins, which were meant to trap the air but were forever coming loose or getting torn. She’d once told Rosalind that she’d often had to spend half a day without breathing, while the tarps were repaired and air was pumped in from the level below.

Sigrid said, “I’ll reserve the word beautiful for the first sight of fertile soil between my fingers.” She glanced across at Rosalind from her adjacent ladder. “Or better yet, my first child born on that soil.”

“Yeah, yeah,” Joanna replied tetchily. “It’s all about the practicalities; the rest is just a distraction.”

“Do you think a thousand people should have died just to give you a pretty ice sculpture?” Sigrid retorted.

“No. But that doesn’t stop me appreciating every part of what they built.”

Rosalind knew better than to urge them to make peace, or even just spare her from having to listen to their nonsense. They’d never actually come to blows over these meaningless quibbles, so if they found the bickering helped them pass the time, who was she to object?

As their last day attached to their birth world wore on, the sun crept below them without actually setting, even as Tvíburi turned gibbous behind the wall of ice. Rosalind couldn’t really discern its shape, but the slowly growing illumination from the west side of the ice ahead of her was all she needed in order to picture the new dawn sweeping over the face of the twin.

For all that the rules of light and geometry rendered everything she was seeing explicable, it remained deeply unsettling. If anything, what shocked her was that these strange sights made so much sense. As a child, she’d experimented with lamps and fruit, visualizing every stage of this journey. For the real sun, and the real worlds, to recapitulate her clumsy shadow play made her feel like someone half prophet, half puppet, unable to decide if she’d shaped this future, or if it had reached back in time and shaped her.

Then again, maybe light was just light, and spheres were just spheres, and the humblest piece of fruit cast its shadow no differently than the world itself.

When the sun finally went behind Tvíbura, leaving the softer glow of their destination to light the way, Rosalind counted the number of annular platforms she could make out above her—and for the first time, it had fallen from the usual eight all the way down to six. At first, she thought she might be losing a couple to the change in the light, but as she passed the nearest of the six, nothing emerged in the distance to make up for it.

“Almost there, almost there, almost there!” Joanna chanted excitedly.

“Do you think we’re blind?” Sigrid replied irritably.

“No, I think you’re entirely insensate.”

Rosalind was beginning to suspect that the only thing that would keep them all from driving each other insane would be the prospect of making the farms big enough to start luring fresh blood from Tvíbura. The six expeditions would amount to forty-eight people in total, but they might not have much time to visit each other’s villages. Only new migrants would swell the numbers in each one, and bring some semblance of normalcy.

As they approached the end of the ascent, even Joanna fell silent. Rosalind saw the five women who’d climbed ahead of her leave their ladders and enter the departure hut. And then she was in there beside them, clinging to a hand rail, watching Sigrid clamber over the edge of the entrance, then Joanna too. She looked around and everyone was there: Anya, Kate, Hildur, Sophie and Frida. She’d wanted someone to be missing, just so they’d have an excuse to climb back down and investigate the absence. But apparently everyone else had been relying on her to be the one who ducked aside and hid on a platform. Joanna should have done it; she was the last, the only one of them with a chance to act unseen.

“Are you all right?” Kate asked.

“Just a bit dizzy,” Rosalind replied.

“Take a long, deep breath,” Kate suggested.

Tower workers had been up here before them, carrying the supplies and preparing them for the drops, but since even the weather on Tvíburi might influence where each glider landed, it had been decided to dispatch both people and provisions as close together in time as possible. When her gaze fell on the exit, Rosalind felt naked without her glider at hand, but if everyone had done their job it would be waiting for her outside, already assembled.

People joked and embraced each other awkwardly in the weightlessness, exchanging their last words before Tvíburi. Anya went through the exit first; there was something comical about watching her carefully sealing in the air behind her, as if that mattered to any of them now. But it would only be a few days before the second expedition began their own ascent, so it would hardly be polite to deplete the pressure in the entire top level ahead of their arrival.

As the others followed Anya, Rosalind hung back. She’d spent most of her life preparing for this moment, and she believed that she and her friends had done everything possible to understand and lessen the risks. But if every jump she’d ever made might have killed her, none of them had induced the kind of dread she felt now. It clamped her hand around the rail beside her so tightly that she feared her injured finger would break again, while every other muscle in her body turned to mush. All this, even with her brothers comatose. You have no idea how lucky you are, she told them. If only she could have slept through the whole journey herself.

Sigrid entered the chamber; only Rosalind and Joanna remained in the hut.

“You first,” Joanna insisted.

“Why?” There was usually no one more impatient.

“I don’t know,” Joanna admitted. “I just like the idea of being alone here for a while. Saying goodbye to the tower on my own.”

“If you don’t come through, you know we’ll come and grab you,” Rosalind joked.

“Only if you can catch me. If I jump down the center of the tower—”

“If you jump down the center of the tower, you’ll fall so slowly that anyone crawling on the ladder could overtake you in no time. In fact, the ice-farmers probably miscalculated: I bet we’re past the midpoint, and you’d actually fall upward.”

Joanna smiled, and gestured at the exit. “Sigrid must be through by now.”

Rosalind pulled herself over to the door, got it open and dragged herself into the chamber. Contorting in the darkness to check each seal, she lost all sense of the direction in which her legs had originally been pointing, until she realized she could recover it by thinking about the doors’ hinges. When she finally emerged onto the balcony, she was the right way up—at least in Tvíburan terms.

She raised her eyes toward Tvíburi. She had never seen it clearly, unobstructed, from any other point on the tower, so all she had to judge this apparition against was the view from the ground. But if the swollen disk was duly magnified, it still did not look close enough to be welcoming. It was not at all like staring down at the ground, not even from her highest jump. It was just a circle of light in the void, and nothing in her instincts promised her that she wouldn’t simply veer off course and vanish into the endless blackness around it.

Joanna touched her shoulder. Rosalind turned and leaned toward her, then pressed her forehead against her friend’s. I can do this, she insisted to herself. What was the alternative? Crawling back down to the ground, mocking all the dead workers and starving farmers who’d given her the chance for a new life? Curling up in the void and drifting away to die?

Anya and Hildur had already started dispatching the supply gliders. Rosalind watched as the two of them maneuvered the next one onto the catapult. At some point, Joanna had argued that the members of the expedition would easily be strong enough to send themselves, and all the cargo they needed, plummeting into Tvíburi’s embrace by muscle power alone—and no doubt that was true, but the consensus had been that a more consistent force was needed if they were to have any hope of arriving within a day’s walk of each other, let alone the supplies.

The eight passenger gliders were tied to a rail at the far end of the balcony, and some of the other travelers were already making their inspections. Rosalind dragged herself over and joined them. She had no trouble identifying her glider; the style and materials were exactly the same as the one that had ended up in pieces on the ice field. She checked every rod and every seam, but whoever had put it together for her had done a good job. Matilda, probably. Rosalind would miss her, though hopefully not for long; Matilda had sworn she’d make the crossing herself at the first sign of greenery on Tvíburi.

Anya wound the catapult again, then she and Hildur fetched the last of the supply gliders. Each of the twelve crates being dropped contained a mixture of items, so that even if only one was recovered there would be no essential tools or provisions that were entirely absent. Rosalind did not believe for a moment that all twelve could be lost, unless they’d miscalculated some detail of the flight so badly that none of the more delicate, flesh-and-blood cargo would survive the journey either. But she still found herself hunting for a reason for her sense of apprehension. The air might be poisonous, the soil might be barren, the wildlife might be fierce and predatory… but those risks had been obvious from the first day Freya herself had suggested raising the tower. Rosalind was only afraid of the dangers no one had thought of before—and her chances of outguessing all her colleagues and predecessors at the last moment seemed slim. She had to reconcile herself to that, just as she’d accepted all the known risks. Just as she’d pictured her body a thousand times, torn apart as it skidded across the ice, she had to picture the eight of them, alive and healthy, gathered in their new village, wailing and screaming at each other that they’d been fools beyond measure for failing to prepare for, failing to bring, failing to imagine… the thing that she could not conceive of.

She closed her eyes. There, it’s done.

She opened them just in time to see the last supply glider slide along the catapult and disappear into the void.

Rosalind grabbed hold of her glider and started dragging it toward the machine. There was no order of departure that they’d all agreed on in advance, but as the flier who’d tested every new altitude from the tower, she did not believe anyone would contest her right to go first, one more time. And she could not hang back, she could not go last. She was strong enough to be the first to die, if that was the fate they were all about to share, but the idea of standing on the balcony alone filled her with an unbearable sense of desolation. Let Joanna take that role, if it was what she wanted.

After Anya finished winding the catapult she helped position the glider, then she and Hildur held it still as Rosalind climbed in beside it and strapped herself in place. They had all rehearsed the procedure a dozen times, almost weightless, in a closed room three levels below. The only difference was that this time there would be no cushioned barrier to bring her to a gentle halt.

With the glider and the catapult blocking her view, Rosalind pictured the scene on the balcony, and judged the time. Too soon, and the act would seem abrupt and alarming, too late and people would start to worry that she’d lost her nerve.

But when the perfect moment came, she didn’t hesitate, she just kicked the release lever. The catapult’s response was too fast for her to analyze; she looked down past her feet and saw the tower below her, a needle of glinting ice that seemed to narrow down to nothing long before it touched the ground—and then even the top of it retreated into invisibility, leaving her with the gray disk of Tvíbura, and beyond its edge nothing but stars.

Above her, the nose of the glider limited her view, but she could see the world’s shadow just beginning to encroach on Tvíburi’s brightness. The progress of the eclipse would give her a sharper sense of time than the slower motion of the arcs of dawn and dusk; the shadow would come and go in slightly less than one seventh of a day, while her journey was predicted to take about one fifth. Until she hit the atmosphere, she would be part of the same majestic gravitational machinery as the twin worlds themselves, and unless the catapult had been egregiously misaligned or mis-calibrated, there would be no real uncertainty in her trajectory until the very end.

She was surprised at how calm she felt now. Once the tower had vanished, she’d had no cues to provide any sense of motion, and it would take a while yet for the tug of Tvíburi to add much to the catapult’s initial impetus. She glanced back down, hopeful for a moment that she might catch a glimpse of whoever had followed her, though she knew that was absurd. If they’d wanted to cheer each other with their presence along the way, they should have contrived some kind of massive, blazing lamp that could burn in the void, turning each traveler into a beacon for the rest.

In the void, the stars were only a little brighter than on the ground, but they were impossibly sharp, and their colors far clearer. Rosalind found it strange that they were all so much bluer than the sun, when they were thought to be suns themselves, perhaps with worlds of their own. But who would ever know that for sure? No telescope could reveal it, and no traveler could endure the journey it would take to find the truth firsthand.

Her mind turned to her mother, but behind the ache of separation she could still find reasons to be content. No one would let her mother starve, and even if a majority of the young people began to leave Tvíbura, having fewer mouths to feed would help make up for the dwindling harvests. The village councils had had generations to plan for the transition, and her mother still had many friends who would be staying behind with her. Tvíbura would not become a wasteland or a graveyard—not in her lifetime, maybe never at all. Let her see her daughter’s farm from afar before she died; that was all that Rosalind could hope to provide for her, but it would be no small thing.

By the time Tvíburi emerged from its twin’s shadow into full daylight, proximity had changed everything. Rosalind had lain beneath the telescope, night after night, sketching maps of this terrain—committing as many features as she could to memory, preparing for the time when she’d lose the luxury of an all-encompassing view. But even those meticulous acts of cartography had never quite made the land real to her, and to see it now with her naked eyes in more detail than the telescope had ever revealed made her feel as if a story that she’d cherished and learned by heart, but never taken to be more than an entertaining myth, was suddenly bursting out from the pages of a book and wrapping itself around her.

The gray mountains were taller, and far more numerous than those of Tvíbura, which suggested that the geysers had always been more active, piling up insanely high deposits of soil fast enough to outpace erosion and allow their own weight, and the passage of time, to solidify them into rock. But even the flatlands rose up from the ice, high enough to prove that they were being constantly replenished. People had argued that if the soil here was the same as Tvíbura’s, then the seeds that must surely have taken a ride on a geyser now and then would have left the twin world covered in grasslands, but Rosalind was not convinced. Even over the eons, the number of chances for a seed to have made the journey and land, undamaged, on anything but ice need not have been so great as to prove that the soil itself was inhospitable.

The storybook world expanded below her, with geysers and mountains retreating into the distance as the ice field commandeered the plot, preparing a thousand-page monologue detailing its every ridge and crack. Rosalind felt a prickling sensation on her skin. The glider itself was steady, but she could feel the panels growing warm around her back.

This was it: she was touching the atmosphere. And she was coming in fast enough for this rarefied upper layer to heat the glider, even before it delivered any perceptible force. She contemplated the gentle heat, refusing to let it alarm her. Joanna had taken her through the calculations: if every scrap of the difference in potential energy between the top of the tower and the surface of Tvíburi was used to raise the temperature of her body, the effect would be about the same as holding her hand a bit too close to a lamp for comfort. To be that hot for too long would be intolerable, then injurious, and eventually unsurvivable—but once there was any kind of wind to cool her, the actual heat she retained would start to fall short of that hypothetical limit. If she could have ensured that all the inflows and outflows of energy were averaged over the descent, she would have had a guarantee that she’d be fine. In reality, it would all be down to details of Tvíburi’s atmosphere that no one had known how to measure in advance.

Rosalind fixed her gaze on the ice, picturing the chilly weather below as the heat shifted from cheerful to unpleasant. The glider began to tremble, then pitch; it oscillated unsteadily, then settled with its nose toward the horizon, leaving her facing straight down. A thin, hot breeze flowed over her body; somehow she’d expected the wind to be cool, as if the air’s two roles were separable, and this merciful intervention would be like an independent bystander coming to her aid. But the truth was good enough: the balance was shifting, and as the hot wind blew more strongly, it also grew less fierce. As the air thickened, and slowed her more and more, it also had the capacity to absorb a greater share of the energy burden itself, and to carry more heat away.

Her view had shrunk to a region much smaller than any of her maps, but she’d retained a sense of the position of the landmarks that had gone out of sight, so she did not feel lost. As the ice field loomed toward her, she picked up lateral speed, flipping through the ever-expanding storybook, glossing over the details of the icy monologue, hoping to reach the end before dark. The air was merely warm now; she opened her throat and took a tentative breath. It was thicker than she’d expected, and carried a strange dusty aftertaste, but it seemed to satisfy her lungs. She waited a few moments, in case there was some delayed adverse reaction—as if her caution really mattered, when in the end she’d have no choice. But when she felt an unambiguous surge of energy spreading to her limbs, she inhaled again, deeply. The warmth and the strange smell made her cough, but the realization that Tvíburi seemed to be welcoming her filled her with equal parts elation, and shock at the stark reminder that the result could easily have been different.

The ice was a blur now, but the glider remained steady; Rosalind couldn’t recall a flight as calm as this. The thicker air could only react more forcefully to her encroachment, but apparently its greater density also helped dampen out turbulence. If the glider broke apart, it wasn’t going to do it in flight. Everything would depend on the landing.

The cool breeze she’d been longing for suddenly arrived, sending her clothes fluttering. She saw the glider’s shadow racing over the ice, unable to outrun its pursuer, and she braced herself for the inevitable meeting.

The runners struck the ground, sliding forward at an impossible speed. Rosalind stared down at the ice, terrified that the frame would break apart while she was moving so fast that the abrasive surface would take all her skin off the instant she touched it. But if anything, the ride kept growing smoother. Maybe the runners had grown so hot that they were simply melting away the rough patches. But if the smallest obstacles could vanish, anything larger would still be fatal.

She kept her body rigid, gripping the handle bars tightly but prepared to reach out and grab one of the bracing rods if the glider deformed and the structure betrayed her.

The betrayal never came. Friction did its work, uninterrupted, and the glider came to a halt, intact.

Rosalind unstrapped herself and knelt on the ground, trembling. Then she crawled out from under the glider and surveyed her surroundings.

The ice field stretched almost as far as she could see in most directions, though if she squinted at the horizon she could make out one of the geysers she’d noticed from on high, and some hills to the north. Tvíburi’s orbit had carried the whole world westward beneath her as she approached through the void, so she’d expected to land well east of the prime meridian; once she explored those hills, she could confirm exactly where she was.

The sun had moved a short way past Tvíbura, but every part of the home world that she could see was still in night. There was something comforting about the utter familiarity of the configuration; she could have looked up on any other afternoon and seen a near-identical sight. Nothing was back-to-front here, nothing was reversed or deranged, on its own terms. By day she saw Tvíbura’s night, and her east was Tvíbura’s west—but if two friends standing face-to-face could accommodate the meaning of left and right, the cartographic version should cause no greater confusion.

Something small and dark in the sky caught her attention. For a moment she wondered if it might be one of the gliders from the tower, but its motion was both too slow and too complicated.

As the thing came lower, she realized that it was a kind of lizard. But instead of holding its limbs outspread, stretching the membrane between them to act as a natural glider, it was moving them in a way that was making the membrane flutter. The action looked bizarre, and utterly counterproductive, but rather than sending the creature plummeting, these strange flutters seemed to be controlling its flight. And when it dropped toward her, instead of continuing to the ground—as every lizard she’d ever observed before would have been compelled to do—it rose up into the air again in a wide, helical trajectory, ascending so high that it disappeared from sight.

Rosalind began weeping with joy. Not only was the air here breathable, there were animals—strange, vigorous animals, who evidently suffered no lack of food. Whatever the absence of grasslands meant, this world had to be far from barren.

And they’d come with seeds, they’d come with tools, they’d come with generations of farmers’ knowledge. All this time, Tvíburi had been waiting to feed her sister’s children.

7

By sunset, five members of the expedition had joined Rosalind at the base of the hills. Anya had chanced on one of the supply drops along the way, and used the enclosed cart to drag the crate with her. The contents included blankets and a small tent, so they set up the tent and crowded in for the night.

There was no sign of Sigrid or Joanna, but Rosalind wasn’t too worried yet. The protocol “head for the nearest landmark to the north” had sent six of them from the ice field to the same hills, but it was not a foolproof recipe for convergence—and when the six who’d met up so far had done their best to mark their own landing sites on a map, it had been clear that chance variations in atmospheric conditions had had as much of an effect on where people hit the ground as the timing of their departure and the systematic libration of the two worlds. It wouldn’t be hard to guess the most likely places where the missing pair might have ended up, and if they followed the rules and waited to be found by a search party sent by the majority, everyone would be reunited before long.

Sleep proved impossible, but Rosalind resisted the temptation to walk out of the tent and start exploring. Many of the plans they’d made together before departing were sure to prove ill-conceived, but she wasn’t going to start her new life with a frivolous rebellion against the sensible consensus that everyone should rest and regain their strength on the first night after the journey.

So she settled for exploring from her blanket: pondering the strange smell of the new world, the effort it took to breath the thicker air and the greater reward it offered, the unfamiliar insect chirps, the deeper tones of the wind.

In the middle of the night, it started raining. No one had thought to set up a container to catch the ethane, so Rosalind went out and did it herself.

When she checked, around dawn, the container was almost three-quarters full—more than enough to keep them all healthy for days. She looked across the ice field and saw two figures in the distance, approaching slowly, arms around each other’s shoulders.

She ran to meet them. Joanna was uninjured, but Sigrid had broken her foot.

“How bad is it?” Rosalind asked, stepping in to support her on the other side to Joanna as they continued on toward the camp.

“It’ll heal,” Sigrid insisted. “It’s a clean break, it just needs a splint.”

“All right.” They had splints, bandages, and disinfecting ointments in every crate.

When Sigrid had been tended to, they left her in the tent to rest and began their sweep of the area to try to locate the remaining supply drops. Rosalind strode across the ice, diligently scanning the ground ahead for anything from an undamaged glider to the sparsest trail of debris, fighting the urge to keep looking up to check that it really was Tvíbura above her.

She was hungry, but that was more out of habit than need. The food they’d brought would have to be rationed carefully, with one meal every second day, but the air alone gave her a sense of vigor.

Around mid-morning, she found one of the supply drops. The glider was intact, apart from a small tear in one panel. She disassembled it and stacked the panels on top of the crate. As she started back toward the camp, she saw another of the flying lizards wheeling above her.

By noon, the travelers had recovered seven crates in total. By nightfall, eleven. They took a vote and decided unanimously to move on to the next stage of the plan; if they ended up desperately short of anything, they could always come back and search again for the twelfth crate.

But Rosalind was hoping that the glider in question had torn itself apart high above the ice field, leaving its cargo to plummet to the ground far short of all the other landing sites. Their luck could not be perfect, and if the cost of that was a broken foot for Sigrid and one missing box of supplies, that would leave her much less nervous than eight travelers entirely unscathed, twelve crates recovered, and some unknown price yet to be paid.

The nearest soil deposit was about two days’ walk north-west of the hills. They decided to send an advance party of four, traveling light, rather than lugging all of their supplies to a destination that might turn out to be unsuitable. Sigrid willingly forfeited her place, then the rest of them drew lots. Kate, Joanna, Rosalind and Anya picked the red tokens.

It was still early when they set out. As they skirted around the base of the hills, Rosalind found herself shooing away mites—or some kind of tiny black insect that fled from her approaching hand, but was too numerous for this discouragement to have much effect. Unlike the ones back home, none seemed to want to bite Tvíburans, but they were still curious enough to spend time exploring the foreigners’ skin, and however many got the message that there was nothing palatable for them here, they clearly had no ability to share that knowledge with the rest of the swarm.

“What are they eating?” she wondered. She had yet to see anything that she recognized as vegetation.

“Each other?” Kate suggested.

“Very funny.”

“There must be something growing up in the hills,” Anya decided. “Some fungus that can draw nutrients out of the rock. Or maybe there are patches of soil that blew in and got trapped.”

Joanna coughed, then burst out laughing.

“What?” Kate demanded.

“I think I just ate one of the insects.” She probed the inside of her mouth with her tongue, then added, “Yeah, it went down, and it’s not coming back. So if I’m still alive tomorrow, we’ll know what we can use for food if we ever get desperate.”

They set up camp at nightfall, with their destination a smudge on the horizon. Rosalind was surprised that they’d spotted it so early; either they’d walked faster than she’d expected, or the mass of soil rose even higher above the ice than she’d estimated when she’d examined its shifting shadow through the telescope.

Halfway through the night, she woke to the sound of something pushing against the tent. She tried to clear her head, wondering if it might have been the wind. Then she heard it again. The fabric wasn’t rustling in the breeze. It was being prodded.

The light of Tvíbura coming through the weave of the tent was bright enough to show her a small inward bulge in the wall, close to the ground, but this offered no real clues about the would-be intruder. Rosalind woke her companions, and took a knife from her pack.

She unlaced the entrance and stepped out. As she came around to the side of the tent, she saw a low, dark shape fleeing across the ice, moving with a rapid, elegant lope, heading north-west.

Joanna appeared beside her.

“Did you get a look?” she asked Rosalind.

“It wasn’t very big. Maybe some kind of cat.”

“Curious enough to give something strange and motionless a poke,” Joanna mused, “but too shy to stick around when an animal of our size emerges. If they’re the kind of neighbors we’re going to have, I can live with that.”

“Let’s hope that it’s our strangeness they’re shy of,” Rosalind replied. “Not a resemblance to something they’ve already learned to fear.”

Their ancestors had hunted Tvíbura’s predators to extinction, but that battle had relied on numbers and resources that could not be mustered at short notice here. Still, all they’d seen so far were a few lizards, aloof in the sky, some insects disinclined to bite them, and one timid cat. Rosalind lowered the knife, which she’d been holding up instinctively. One more day’s walk, and they might at least discover what lay at the very bottom of the food chain.

As they drew nearer to their destination, it resolved into a high plateau. The hills where they’d met probably hadn’t been much taller, but the color of this material was completely different: a rich brown, just like the most coveted soil back home. The gray of the hills here matched, almost exactly, the gray of the hills and mountains on Tvíbura, so why should other comparisons not hold? Rosalind couldn’t explain why a giant mound of soil with no grass to bind it hadn’t simply blown away, but she refused to believe that they were headed toward nothing but a useless slab of rock.

By mid-afternoon the wind was growing dustier, and the ice around them less pristine. Rosalind ran a finger over the ground then put it in her mouth; it tasted of soil. If she could breath Tvíburian air, belched up from Tvíburian oceans, what was to stop the geysers here from delivering soil that the plants of her home world could feed upon?

The closer they came to the plateau, the less it looked like desiccated, ancient rock. Kate said, “That’s ripe for farming. I can smell it!”

Joanna broke into a run, and this time Rosalind joined her. They sprinted together over the brown muddy ice, shouting exuberant taunts at each other as they took turns gaining the lead.

When they’d almost reached their destination, Rosalind stopped and glanced back toward Kate and Anya, who were proceeding at their usual unhurried pace. She felt slightly foolish, but she didn’t care. She had no more patience left.

She turned to examine the steep incline ahead. Where the approach to the plateau met the ice, the soil had spilled out and left a thin, loose coating, but once it started to rise it became pitted and clumpy, not at all like the side of a sandpile. She caught up with Joanna at the base of the slope.

“Are these some kind of roots?” Joanna wondered, squatting down to examine the tangle of pale, fibrous strands that poked out through the soil.

“That’s what they look like,” Rosalind agreed. “But the roots of what?”

They started up the slope, supporting each other, judging each step carefully as they negotiated the treacherously porous surface. The soil kept crumbling beneath their feet, but never catastrophically; their weight seemed to be collapsing a succession of small, air-filled spaces, but the roots were so tightly woven through the soil that it was impossible to start an avalanche.

When they came to an opening that might have been either a cavern formed by chance from a gap in the roots, or the mouth of a burrow dug by an animal, they skirted around it; this wasn’t the time to start pestering the neighbors. The ascent was growing arduous, but Rosalind had no intention of resting or retreating. There was not much daylight remaining, and she did not trust the light of Tvíbura to reveal everything they needed to know.

Finally, they staggered up onto the top of the plateau. The surface ahead of them stretched into the distance, roughly level as far as Rosalind could see, but as she stepped gingerly forward it was clear that it was no smoother or less porous than the slope. She knelt down and probed the ground with her fingers. The “roots” were still tangled with the soil, but they seemed oblivious to their change of circumstance. There were no stems, or flowers, or leaves protruding from them into the air; in the distance, the ground looked lifeless, just as it had through the telescope from Tvíbura, but each time Rosalind took a few more steps and checked again, she found the same tough, pale filaments locking up the soil.

Joanna said, “So this is Tvíburi’s natural vegetation? Its idea of grassland?”

“Apparently.” Rosalind didn’t think these strands could be something like Yggdrasil roots—part of an organism that drew its nourishment from below the ice, and which had merely trapped the soil by chance. This plant—or colony of plants—was living off the bounty that the geysers had rained down onto the ice, stabilizing it much as the grasses on Tvíbura would have done, but feeding so well on the soil itself that it had no real interest in sunlight.

“So how do we clear a field, out of this?” Joanna asked. “A scythe, a plow?”

Rosalind took the knife from her pack and knelt down again. There was so much soil here: enough for a thousand farms. And nothing to fight the crops for their view of the sky. But when she plunged her knife into the ground, it was impossible to move the blade sideways. The soil’s existing tenants—invisible from a few strides away, let alone from across the void—were nonetheless so numerous, and so strong, that it was like trying to carve into solid rock.

8

“Maybe the other farmers are having more luck,” Frida suggested. “If they’ve found better soil, or found some trick that we’ve missed to deal with the tanglers, they could be thriving already, while we’re just wasting our time.”

Rosalind looked around the tent. The last time the same idea had been raised, people had still been clinging to their pride: every group was meant to be self-sufficient, capable of creating their own foothold in the new world. But now she sensed that most of her colleagues were so despondent that they’d be willing to seek help anywhere.

“The soil itself is perfectly fine,” Hildur insisted. “The seeds all germinate, before they’re choked by the tanglers. If we could just transport enough soil away from the plateau, and set up a new, pristine field out on the ice, the crops could grow there, unmolested.”

“And what’s supposed to hold the soil in place, while we’re waiting for the seedlings to spread their own roots?” Frida asked.

“We carve trenches into the ice,” Hildur replied. “Deep enough to trap the soil, to shelter it from the wind. But once the crops become established, we can start smashing the walls between the trenches, one by one, until we end up with a continuous field.”

Rosalind couldn’t decide which part of this plan would take the most work: hacking up the ice to make the trenches, or filling them with soil when every handful had to be wrestled out from between the tanglers.

Anya said, “I think it’s time to try everything. My vote would be to send a couple of people to tour all the other soil deposits in the region; there might be something we can learn from every one of them, whether or not there are people trying to farm them. But we should also start work on testing Hildur’s idea.”

Joanna said, “And what about my idea?”

Anya scowled. “If it kills you, we lose you and your brothers—”

“If it kills me, no one else needs to waste their time wondering about it.” Joanna laughed softly. “I could easily have died in my glider—revealing nothing new or interesting about this world—and no one would have treated that as a calamity!”

Rosalind said, “When you ate the berries that the cats eat, you were sick for four days.”

“That was worth knowing, wasn’t it?”

“Only if you learn not to take the same risk again!”

Joanna sighed. “It wouldn’t be the same. The tanglers want the cats to eat those berries, for whatever reason. They’ve made them nutritious for that particular animal, and they must get some kind of benefit in return. Maybe the cats travel far enough to excrete the seeds in places where the plant couldn’t send them by any other means. But the cats don’t eat the roots; nothing we’ve seen does that. And maybe if the parts the locals relish make us sick, the parts they avoid will have the opposite effect.”

“There’s no logic in that,” Sigrid protested.

“I didn’t claim it was a syllogism,” Joanna replied. “But it’s still a possibility, until someone tests it.”

Anya said, “Let’s have a break to think things over before the vote.”

Rosalind was glad to get out of the tent; just standing beneath Tvíbura reminded her of how many supposedly impossible problems their predecessors had managed to solve. They could not come this far and fail. There was fertile soil all around her; all they needed to do was prize enough of it out of the tanglers’ grasp. Hildur’s proposal was daunting, but none of them were afraid of hard work. Rosalind tried to picture the expression on her mother’s face when she saw the first farms rising up, not on the original soil deposits that had been mapped generations ago, but on their borders.

Joanna approached. “Are you going to vote for my plan?”

Rosalind laughed, exasperated. “What plan? I can still smell the vomit from when you tried the berries. What was your argument then? ‘Look at how strong and healthy the cats are!’”

“It’ll be a risk,” Joanna admitted, “but it’d hardly be the biggest one we’ve taken. And it won’t be easy to poison myself; those roots are tough. It’ll take half a day to slice them up, and the rest to chew the pieces.”

“Which is why we need to keep trying to grow actual food,” Rosalind replied.

Joanna said, “None of these proposals are mutually exclusive. And believe me, I’d prefer to eat something that grows back home—though with turnips, honestly, would there be any difference? But we need to know exactly what we can and can’t eat here, even if it’s just a matter of having something to fall back on if there’s a shortage of our own crops in the future.”

Rosalind had no problem with planning for contingencies. It was the idea of making do with the tanglers that dismayed her.

“If we can’t grow our own crops,” she said, “how will anyone know that we survived? How will they know that it’s safe to follow us?”

Joanna nodded grimly. “If the famine doesn’t break, there’ll be nothing more important than letting people know whether or not they can escape it here. But if we can find a way to feed ourselves without covering the soil with our own kind of crops, we’ll just have to find another way to get a signal across the void.”

Anya called them back in for the vote. In the end, everyone agreed to send emissaries in search of the other expeditions, and the vote was five-to-three in favor of testing Hildur’s back-breaking plan.

But only Joanna voted for a trial of the tangler roots’ culinary potential. Rosalind had tried to be objective about it, but she couldn’t. She did not want to learn that there was a way to keep on living while everyone they’d left behind starved to death.

As sunset approached and the other members of the team put down their picks and headed for the tent, Rosalind decided to keep working. She had almost come to the end of her second trench, and she wanted the satisfaction of finishing it before she slept.

Her shoulders ached, and she was famished, but each time she swung the pick, the spray of blue-white chips flying off the ice-face was all she needed as proof that she was making progress. This was how they’d finish the task: one strike at a time, over and over, until it was done. Tvíburi had made the job harder than it had to be, in ways she’d never expected, but their patience would wear the world down. Tvíburi would feed them, willing or not.

Her brothers squirmed and hissed, disturbed by her labors, but she knew they wouldn’t grow any calmer when she stopped to rest. They’d woken from their long sleep more ardent than ever, and though she could hardly blame them for the expedition running out of pessaries, they ought to have been capable of noticing how poorly fed everyone was. Who tried to bring children into a world without crops?

“Rosalind? Is that you?”

Rosalind looked up to see a lone figure approaching across the ice. In the twilight, she couldn’t make out the woman’s face, but she knew the voices of her seven fellow villagers, and this wasn’t one of them.

She put down her pick. “Your eyesight’s better than mine,” she called back.

The woman laughed, and strode forward to meet her.

“Erin?”

“Your eyes are still working.” Erin removed her pack and they embraced.

“How’s your group?” Rosalind asked. “Did everyone land safely?”

Erin looked down. “We lost Miranda.”

“I’m sorry.” Rosalind hadn’t know Miranda well, and she decided not to reopen the wound with more questions.

“And yours?”

“We were lucky. Everyone survived.”

Erin turned and surveyed the trenches. “I see you’re trying the same thing as we did.”

“You’ve done this too?”

“Yes.” Erin hesitated, then added, “I should probably tell you about our experience.”

“You’d be welcome to.” Rosalind gestured toward the tent. “Come and rest, first. How long since you’ve eaten?” Erin looked remarkably healthy for someone who’d been walking for days, but it would still be impolite not to share what they had with her.

“Oh, I’m eating right now,” Erin replied cheerfully, opening her mouth to expose a half-chewed, fibrous mass.

Rosalind was startled. “You’re eating tanglers?”

“That’s not what we called them, but yes. Just the roots. You do know the nodules are no good?”

She had to mean what Joanna had called berries, though they sprung from the tanglers’ roots, and could only be plucked easily from the walls of an animal’s burrow. Rosalind said, “That was made very clear.”

Erin poked a finger into her mouth and dislodged the mass from around her teeth, shifting it to the other side.

“What else is your group eating?” Rosalind asked. The roots seemed to take so much effort to masticate that it was hard to believe the process didn’t consume more energy than it yielded.

“Parts of the voles. The cats are too hard to catch. I know, the voles eat the nodules too, and some of their organs seem to concentrate the unpleasantness, but most of their flesh is fine.”

Rosalind had more questions, but she led her guest toward the tent. “Frida and Joanna are off on a tour of their own,” she said. “They might even have stumbled on your people by now.”

“I have a map with all the villages on it,” Erin replied. “Or I will have, once I add this place. So if you tell me which way they were going, I can tell you who they will have met first.”

They entered the tent, and everyone embraced Erin. She refused all their offers of food, and the seven of them sat down in a ring on the blankets. They had no fuel for the lamps anymore, but there was enough light from Tvíbura to let them see each other’s faces.

Once the pleasantries were out of the way, people started quizzing Erin about her village’s agricultural experiments.

“We tried putting soil in furrows in the ice,” she explained. “The first time, we did it close to the plateau, as you’ve done—to make the transport easier. But within six or seven days, there were… I think you call them ‘tanglers’… growing in all the furrows. We assumed that the seeds must have blown in on the wind.”

So much for our own efforts, Rosalind thought. But at least they’d now be spared wasting any more time on a flawed method. And she could feel the tension growing as people waited to hear about the next step: the one that actually worked.

“We repeated the whole thing much farther away,” Erin continued. “We had guards watching, day and night, to shoo the cats away, in case they came and shat seeds into our precious soil. But the same thing happened. The tanglers appeared, just as quickly as before, and nothing of our own could grow.”

“How is that possible?” Hildur protested. “Even if the wind is blowing the seeds far and wide, how could there be as many of them at a greater distance?”

“We must have brought them there ourselves,” Erin replied. “The soil must be full of them, and they’re either too small to discern, or too similar to the particles of soil to be picked out by inspection. Whatever the cats are spreading, it can’t be the only means these things have of reproducing. We’ve tried washing the soil, sieving it through fabric, tossing it in the air and only using the parts that fall at different distances—hoping the wind will separate out the seeds and leave us with something we can use. But so far, whatever we do, we either end up with useless gray dust in which nothing at all will grow… or we end up with rich, brown soil full of tanglers.”

9

Rosalind couldn’t sleep, so she left the tent and walked out across the ice. It was close to midnight, with Tvíbura almost entirely in shadow.

She paced the encampment, repeating the calculations that had kept her awake, hoping she might have made an error that she could detect now that she was fully alert. But the results remained the same. Even if the people of all six villages devoted every waking moment to digging trenches in the ice and filling them with soil, it would take at least three generations to spell out an unambiguous message in letters large enough to be read through a telescope.

Maybe a written message wasn’t necessary; any clearly artificial structure would demonstrate that the colonists were still alive. In the absence of recognizable farmland, that would still prove that there was a source of food here. But would anyone actually make the crossing from Tvíbura on no other evidence than a few baffling lines appearing in the ice? If they were desperate, if they were starving, maybe a handful of people would interpret the peculiar artefacts as signs of hope; maybe there would even be enough of them to support each other in all the tasks they’d need to perform to make the crossing safely. But it was hard to imagine an influx so great that it became self-sustaining, with the new arrivals so numerous as to add significantly to the artefacts’ drawing power. Most people would need a clear promise that a better life awaited them on Tvíburi—and most people would find that unimaginable in the absence of the kind of plants they were accustomed to eating.

She heard a rustle of fabric, and turned to see Joanna emerging from the tent.

“Are you thinking what I’m thinking?” Joanna asked.

“Possibly, but tell me anyway.”

“We need to do something with the root cuttings.”

Rosalind took a moment to understand her meaning; most of the talk about “roots” that she’d heard lately had concerned the tanglers.

“Do what with them?” They’d brought the Yggdrasil cuttings with them on the chance that, if there was a local variety that lacked some of the qualities needed to grow a second tower, the two kinds might be spliced together. The idea itself wasn’t entirely fanciful; farmers had sometimes succeeded with heterogeneous grafts for other kinds of plants. But there was no sign of any local version of the Yggdrasils at all.

Joanna said, “Drop them in a hole that takes them all the way down to the ocean.”

“Into a geyser?” Rosalind was bemused. “Even assuming that they find the conditions amenable down there—with no competitors as brutal for them as the tanglers are for the crops—how long do you imagine it would take for the tree to get its roots up to the surface?”

“I don’t know,” Joanna confessed. “Generations, for sure. But that’s no reason to put it off. If we don’t do everything in our power to make it possible to get word back to Tvíbura, people are going to go mad. It’s hard enough accepting that there’s probably no way to achieve that in our lifetimes, but at least we have the tradition of the tower-builders to fall back on: if they could work for something that they knew they wouldn’t live to see for themselves, we can do the same. It won’t be enough to make anyone content, but it might be enough to keep us from losing hope.”

Rosalind couldn’t find much comfort in this definition of hope: some small chance of the cuttings thriving in the ocean; generations for the roots to break the surface, then generations more for a second tower to be grown. She wanted her friends to join her before she died. She wanted her mother to live long enough to know that the expedition had succeeded.

But she had no idea how to make those things happen.

“We don’t seem to have any other use for the cuttings,” she conceded, “and if half the villages keep theirs, just in case, I can’t see any harm in trying.”

“So you’ll vote with me on this?”

“Yes.” Rosalind stopped to ponder the practicalities. “Which geyser are we talking about?”

“The closest one to the closest point to Tvíbura,” Joanna replied. “I don’t care how far I have to walk, but if the Yggdrasil is to be of any use for tower-building, we need the roots to emerge in the right position.”

“The terrain around there looked a bit tricky.” Rosalind had found the strangely sculpted ice deposits quite beautiful when she’d been gazing down at them through the telescope, but she’d never contemplated trying to scramble over them.

Joanna didn’t dispute this assessment. “So if you’re coming with me,” she said, “don’t forget to pack plenty of rope.”

The geyser rose highest around midnight and noon, dying away completely by sunset and dawn. Rosalind watched the white column ascend every morning, wondering if the glimmering haze contained a few droplets of water, or if the spray bursting out from the buried ocean froze entirely into powdered ice by the time it reached the surface. It was strange to think that the same eruptions had once been so common on Tvíbura that everyone in the world would have seen at least two or three in their lifetime, and many would have witnessed them up close. The marvel she was approaching had been entirely commonplace.

In the evenings, they often saw cats out on the ice, and by day, lizards overhead. No animal here was quite the same as anything back home, but they seemed too close to Tvíburan species to have no kinship with them at all. With plants it was another story, but perhaps the tanglers were the oldest, purest Tvíburians, and they’d conquered their territory long before any Tvíburan seed tried to gain a foothold. Rosalind could not imagine a cat being flung from world to world by any means and ending up alive, but if ancient lizards had flown in the skies of Tvíbura when its own air was thicker, it was not inconceivable that they could have survived the crossing.

By the fourth day of their journey, the geyser was beginning to resemble an ephemeral version of the tower: a white streak bisecting the horizon and stretching toward the zenith, tapering to invisibility long before it actually came to an end. There was a faint, low rumble in the ice that presaged its appearance, catching Rosalind’s attention just in time for her to follow the top of the fountain as it rushed into the sky.

Though the column of ice-dust came and went, it rose from a permanent base. It was hard to discern when the geyser was flowing, but in the late afternoon, when the sun had moved on to squeeze the ocean out through other vents, a low, broad cone of ridged and jagged ice emerged from the haze.

On the morning of the sixth day, the hard, flat surface of the ice field, compressed by time and worn smooth by wind and dust, began to acquire a smattering of fragile encrustations, shaped more like delicate sculptures than anything that belonged to the realm of geology. Rosalind did her best to avoid them, but as they grew more common she grew impatient with the need to weave a complicated path around them, and started crunching them underfoot.

“Why don’t they just lie flat?” Joanna asked, irritated but still curious. She squatted down to inspect one of the deposits. “You know these things are mostly thin air? They’re like shrubs sprouting ever finer branches, taking up space without actually containing much ice. But I don’t know what makes the ice from the geyser so special that it doesn’t fall straight to the ground.”

Rosalind pondered this. “The ice dust might fall straight to the ground, but if there’s vapor it could condense around whatever’s already there.”

Before long, there was no unencrusted ground remaining; everywhere they trod, ice crumbled beneath their boots. And with each step, they found themselves sinking a little deeper, demolishing ever taller structures before their soles ended up on solid ice and they were left ankle-deep in the surrounding deposits. But then, even more disconcertingly, the lower portions of the ice-shrubs began to resist their weight—with the upper parts still collapsing, leaving them perched on the jagged remnants.

“How did people ever do this, back on Tvíbura?” Joanna wondered.

“What makes you think they were ever stupid enough to try?” The view from on high had been misleading; Rosalind had been prepared to face a craggy landscape built of solid ice, but no amount of rope was going to render this terrain traversable.

“I wouldn’t call it stupid,” Joanna protested. “How could you know there were cracks in the ice going all the way down to the ocean, and not want to take a look? And just because we’re unprepared, it doesn’t mean they were.”

Rosalind could recall children’s stories where people both innocent and wicked had been cast into the chasms by their antagonists. But those tales had been woefully light on detail about the method of approach.

Joanna cried out in pain, and spread her arms to stay balanced as she tried to take the weight off her right foot.

“How bad is it?” Rosalind asked.

“It stabbed through the sole of my boot, but I don’t think it went far into my foot.”

Rosalind pictured the two of them walking with Joanna’s arm across her shoulder; anywhere else it would have been the right thing to do, but here it was only likely to make things worse.

Joanna raised her foot and brought it down again slowly, angled slightly.

“We need to get back on solid ground,” Rosalind said.

“I’m not giving up!” Joanna replied angrily.

“I never said we should. But you need to put a bandage on that. And then we need to find a better route.”

As they were retracing their steps, Rosalind heard the usual rumbling and felt the wind rising up, blowing toward her from the ice field. She turned to see the geyser ascending; they were so close now that the column of white haze blotted out a third of the sky. As she raised her eyes toward the vanishing point, it looked as if the torrent of ice dust was tumbling down, falling toward Tvíbura—as if their dying home was reasserting its power. But Tvíbura had nothing to do with it, and even the sun was cheating: squeezing the trapped, subterranean ocean, raising the pressure in one direction and lowering it another. Down was still down, and no quirk of gravity was going to lift her up off this accursed ground and drag her into the sky.

She looked down again and kept walking gingerly across the perilous surface. After a while, she felt an odd sensation on her skin; she inspected her palms, and saw a faint, branched pattern catch the light. The fine coating of ice cracked and splintered as she flexed her hands. She blinked, and felt the same thing happening on her eyelids.

They set up camp out on the ice field, and Joanna rested her bandaged foot. “I don’t know how long it’s going to take us to learn to repair boots with anything Tvíburian,” she lamented. “Did you see the fabric Hildur wove from tangler fibers? After one day wearing that I think it would take most of your skin off.”

“We’ll learn how to treat the fibers to make them softer,” Rosalind asserted, trying to keep them both optimistic. “And we still haven’t cataloged all the less common plants. Nobody made the plants on Tvíbura for our benefit; we just discovered ways to use them, over time. It will be the same here.”

“Maybe.”

The next morning, they left their tent standing and set off in a broad arc around their target, hoping that a combination of influences—the prevailing winds, the topography of the ice field, and the shape of the chasm itself—might direct the falling plume of ice dust and water vapor in such a manner that a path was left clear. But while the edge of the region plagued by encrustations moved closer to the chasm for a while, it soon reversed direction and forced them away again.

It took them all day to come full circle.

Joanna limped to a halt in front of the tent. “We need to come back with wooden boards we can put under our feet,” she said. “Strapped to our boots, to spread the weight over a larger area.”

Rosalind said nothing, but she suspected that that would just delay the inevitable: they might succeed in crossing more of the fragile ice before it gave way beneath them, but when it happened they would only plunge deeper into the pile of icy spears and blades that the geyser had been stacking up around itself since its inception.

She looked up wearily toward Tvíbura. A lizard was circling overhead; she’d seen so many of them close to the geyser that she was starting to wonder if there was some kind of oceanic insect that they were feeding on—snatching it out of the air as the geyser delivered it, stunned or dead, into this strange, hostile world that the poor creatures could never have imagined existing.

“I know how we can get the root cuttings into the chasm,” she said.

“With my ice shoes,” Joanna replied, puzzled, as if the matter had been settled.

“We saw some cliffs to the north,” Rosalind reminded her. “Not much farther from the geyser than we are now.”

“What has that got to do with anything?”

Rosalind said, “The ground’s not safe to walk on, but the lizards have no trouble with the air here. I’ll glide off the cliffs, and let the updraft carry me over the chasm.”

10

Rosalind took her time, studying the lizards as closely as she could, contemplating the modifications she would need to make to her glider if she wanted to mimic the way they spiraled up around the geyser. Trying to create panels that undulated like the lizards’ membranes would be absurd, but adding a system of struts and levers that allowed her to flex the whole shape slightly, giving it enough asymmetry to force it to swerve left or right, seemed like a reasonable ambition.

She made the changes, then carried her glider to the top of the plateau to test the new design. But as she ran toward the edge, her courage failed her. She stopped and knelt down on the tangler-infested soil, trembling in horror at the risk she’d almost taken. If anything had gone awry, she could have dashed her skull open on the ice below.

She left the glider where it was and made her way carefully down the slope, relieved to have abandoned the whole insanely reckless notion. It was only when she was back on level ground that she paused to reflect on the reasons for her change of heart.

Rosalind stood on the ice for a long time, weighing up her options. Then she went looking for Sigrid.

“I think it’s time,” she told Sigrid. “We know we can survive on the tanglers and the voles. We can feed and shelter ourselves. And we understand the animals here well enough not to fear them. Nothing’s certain, but someone has to be first. And I know you’d make the best mother, out of all of us.”

Sigrid was amused. “If your brothers are annoying you, just say so. You don’t need to flatter me.”

“But you agree?”

“Yes. When do you want to do this?”

“Tonight,” Rosalind replied. “Up on the plateau, where we’ll have some privacy.”

As the time approached, Rosalind tried to keep her mind on other things. She spent the afternoon helping Hildur with her weaving, then she chatted with her fellow villagers, pursuing every idle topic that arose, prolonging each distraction for as long as she could.

“Are you all right?” Joanna asked her.

“I’m fine.”

“How are your experiments with the glider going?”

Rosalind said, “There are some aspects that are proving trickier than I expected. But I think I can sort them out.”

At sunset, she left the tent on the ice field and headed up the slope. There was a second tent, on the plateau, that had been largely abandoned since their farming experiments had failed. As Rosalind entered, Sigrid called out to her; she had followed close behind.

“Don’t be nervous,” Sigrid told her, as they knelt down together in the near darkness. “Before I joined the expedition, I let one of my brothers breed. It only seemed fair, before they faced the long sleep. And I can promise you, it’s not that difficult. Just relax, and he’ll know what to do.”

They loosened their clothing and brought their bodies together. Rosalind felt all three of her brothers scrambling to take advantage of the opportunity, but the struggle didn’t last long. The winner emerged, protruding from between her legs, crossing the narrow gap between the women, determined to father a child.

Sigrid gasped, but didn’t flinch; she wrapped her arms around Rosalind to keep their bodies from being pushed apart. Rosalind listened carefully to her labored exhalations, trying to judge the progress of the act. She had no experience at all, but she’d heard enough talk from other women to know what to expect.

Sigrid shuddered, then relaxed. Rosalind pulled away from her as quickly as she could, then reached down and took hold of her retreating sibling before he could disappear. She got to her feet, hitching up her trousers with her other hand, and headed out of the tent.

“Are you all right?” Sigrid called after her.

“I’m fine,” she replied. “It’s just the pressure on my bladder…”

Rosalind walked carefully across the uneven soil, afraid of tripping on the tanglers. When she was far enough away from the tent, she knelt down on the ground and groped in her pocket for the knife.

Before her brother could sense what was happening and try to change her mind, she pushed the blade into his body and forced it through to the hilt. He squealed and thrashed, but the handle of the knife was jammed against her thighs, so the more he tried to retreat to safety, the more damage the blade wreaked.

When he stopped moving, Rosalind cut off everything that protruded and buried it in the soil. She was weeping softly, but she hardened her heart. He’d fulfilled his purpose; she’d given him that. She would do the same for the other two.

She had no choice. However repugnant this fratricide, she couldn’t spare them. She had her purpose too.

Once Rosalind had perfected her technique, she demonstrated her modified glider to the rest of the village: launching off the plateau, and completing a rough circle over the ice before landing.

Afterward, they gathered in the tent and she sketched out a plan that she hoped they’d find plausible.

“You’ll start flying while the geyser’s active?” Kate asked, troubled by the notion.

“It’s the only way to get above the chasm,” Rosalind explained. “I need a strong updraft. Even starting from the cliffs, if I tried to approach while the geyser was quiet, I’d just crash into the needle-ice before I was even close.”

“So you approach, you circle around waiting for the geyser to stop, then you swoop over the chasm, drop the root cuttings… and hope you get back to solid ground before you lose altitude?”

“Exactly,” Rosalind agreed. “But when you say ‘hope’ that makes it sound like a huge gamble. I’ll make sure I’m high enough to start with so it won’t be unlikely at all.”

Kate looked dubious. “And when you say ‘I’ll make sure’ that makes it sound as if you’ve done all this a thousand times before.”

Rosalind said, “Either I try it at the real site now, or I give up. I’ve practiced as much as I can.”

They voted in her favor, six to two, with only Kate and Frida unconvinced. Joanna would accompany her, since she knew the terrain already.

As they left the tent, Sigrid touched her shoulder and whispered, “Good news. Your brother should be happy.”

Rosalind said, “We should all be happy.”

“We will be,” Sigrid assured her, “when we see the child born.”

When they set out for the geyser for the second time, Joanna was uncharacteristically subdued. Rosalind wasn’t sure what was troubling her, but after a day walking in near silence, she tried to break the mood.

“Are you annoyed that no one went for your ice shoes?” she teased her.

“Not at all,” Joanna replied. “I’m sure the glider’s a better idea.”

“I’ll be careful,” Rosalind promised. “I know how important this is.”

They were halfway through raising the tent when Rosalind felt a cramp in her abdomen. She excused herself and walked away across the ice, getting as far as she could before the pain stopped her, then arranging her clothes to conceal as much as possible and hoping that it looked like she was defecating. She’d thought her body would expel the dead tissue swiftly, and when it didn’t happen within a day or two she’d wondered if she’d somehow resorbed it. But now all three of the shrivelled roots came out, in a rapid succession of bloody convulsions.

She squatted on the ice, shivering, trying to compose herself. Whatever happened at the geyser, at least one child was coming. She’d have a niece to survive her; she had to take solace from that.

By the time she got back, Joanna had finished with the tent and was lying inside, feigning sleep. Maybe she knew about Sigrid, and Anya, and Sophie, and was hurt that Rosalind hadn’t confided in her. But if they started talking about the subject at all, it might be impossible to stop.

“Sleep well,” Rosalind whispered. She laced up the entrance and lay down on the blanket, hoping they wouldn’t be disturbed by the cats.

They veered north as they approached the geyser, following a gently sloping route to the top of the cliffs. Rosalind kept seeing lizards circling the chasm, and if that in itself promised nothing, at least it was more encouraging than their absence would have been.

“Someone took an awful lot of ink from the stores, just before we left,” Joanna said, apropos of nothing.

“Really?”

“You know how much I use, myself. So I couldn’t help noticing what was missing.”

Rosalind said, “We’ll find a good substitute eventually. The right kind of plant resins, the right kind of minerals… people have just been busy with other things.”

Ahead of them, the geyser erupted into the sky. Joanna stopped. “Do you want me beside you on the cliff, or do you want me to hang back?”

Rosalind didn’t know how to answer that. Joanna walked up and embraced her. “You know it might not work?” she said. “I’ve tried to estimate the velocity, and I think it might be close, but it’s hard to make the measurements precise.”

“I know. But I need to try.”

“Yeah.”

Rosalind tightened her hold on her friend and imagined retreating, the two of them walking back to the village together. Then she released Joanna and stepped away. “You should stay here,” she decided. “Just tell the others I got the cuttings in.”

“All right.”

Rosalind turned and walked up the slope toward the cliff. A dozen or so strides from the edge, she took off her pack and began assembling the glider. When it came to the runners she hesitated, trying to decide between the disadvantage of their weight and the protection they offered. She should have made a judgment on that before she even left the village. But she didn’t have time to agonize; habit took over, and she snapped them into place. The ritual, completed, felt right now.

“Don’t look back,” she muttered. She’d lost track of how far away Joanna was, but if she turned for a last farewell it would only be harder for both of them. She put the cuttings in a pouch tied to her belt, strapped the glider onto her back, then ran toward the edge of the cliff as fast she could.

The wind was already behind her, drawn inward and upward by the geyser’s flow. Her feet were barely touching the ground, and as she stepped off the cliff she ascended. Below her, she saw the fractured cone of uncrossable ice spread out in all its glittering, glorious irrelevance; she hooted down at it with delight and derision.

She looked up into a wall of white haze, and twisted the glider, sending it swerving right. This close, the geyser itself was too wide and diffuse to navigate by; she turned back to the ground, taking her cues from what she could still see of the cone through the ice-dust. She was rising faster than she’d expected; all the rehearsals in her head had played out far more slowly.

The cone disappeared, leaving her engulfed in whiteness everywhere she looked. She sent the glider left, and pictured it ascending in an ever-narrower helix. Was she over the chasm? It was impossible to tell. But if she waited any longer, and rose any higher, it would only increase the chance that anything she dropped would be blown aside on its way down.

She opened the pouch and watched the cuttings tumble away; as strong as the updraft was, they were dense and compact enough for their weight to overcome it. Ice was forming on her hands and face; she wanted to grimace, but she was afraid the fragments would cut her, even blind her.

All that mattered now was gaining speed. The whole flow of the geyser couldn’t escape Tvíburi’s gravity, or there would be no cone of fallen ice around it, and no soil added to any of the plateaus. But that didn’t prove that every last particle the geyser emitted fell back to the ground. She just had to find the fastest portion, emerging from the very center of the chasm where friction with the walls had taken the least toll.

She turned the glider cautiously farther to the left, and felt an unmistakable tug as the air and ice-dust pushed harder against the panels. She settled into the flow, leaving her body almost weightless, then tried again, feeling her way into a faster current. There was nothing to see, nothing to guide her, but she found the right direction, over and over, until there was nowhere left to go.

The haze darkened; the sun had gone behind Tvíbura. The ocean below was being forced up into the chasm with as much pressure as it ever would be. Rosalind took a moment to inhale the sweet, rich air. On the ocean floor, the tiniest living creatures fed on an entirely different gas, created by nothing but water and hot minerals, and then exhaled this beautiful waste. If they hadn’t existed, living out their strange lives in that hidden realm, nor would she.

The air grew thinner, and the haze dispersed. Rosalind watched the shadow of her home world racing across the ground. As far as she could tell, she was still ascending; the geyser had given her all it had to offer, and the only question now was whether that had been enough.

She thought about her mother, waiting for news of the first hint of Tvíburian crops. What would she think, when she learned of a very different discovery, closer to home? It might not be apparent who the messenger had been, but there were people who would recognize the smallest quirks in the style of any glider. Then again, that much of the structure didn’t need to survive the landing; only the message itself had to arrive intact.

By the time the shadow sped away below her, the whole of Tvíburi had shrunk to the kind of disk she’d seen from the top of the tower. Inasmuch as she could discern her own motion at all, she was traveling west far faster than she was ascending; though she’d shared the speed of the rotating ground when she’d departed, this high up she would have needed a much greater eastward velocity to remain above the same spot. But fleeing to the west also meant fleeing Tvíbura. She might have crossed the line where it would still capture her; it might be slowing her escape at an imperceptible rate that would still be sufficient in the end. Or she might be destined to return to Tvíburi, far from the geyser, with nothing to do but start the long walk back to the village.

It was impossible to tell. She’d done her best, but her trajectory was out of her hands now. If she glided down onto the ice field, as smoothly as she’d first arrived, would she reproach herself for failing or would she rejoice that she’d been spared? Even with her brothers gone and her mind untainted, how could she want anything but to live?

Below her, the landscape kept changing, but the cycle of day and night seemed held in abeyance. She couldn’t quite be outracing the sunset, but as time stretched on the disk of Tvíburi remained fully lit. Rosalind closed her eyes and pictured herself suspended in the sunlight forever, perfectly balanced between every hope she’d held for herself, and every hope she’d held for her people. Never falling, never coming down.

She had not done everything. The runners were the heaviest parts of the glider, and they could only serve their purpose if she failed. She should never have brought them with her.

She opened her eyes and reached down with both hands, feeling for the clips that held the runners to the frame. There were four clips on each side; she loosened them all, then worked the runners free.

Before she could talk herself out of it, she summoned all her strength and flung the runners away, sending them back down toward Tvíburi. She watched them retreating, trying to guess their speed, hoping that the small impetus she’d given the glider would make a difference.

She was naked now; wherever she landed it would be unsurvivable. She was every bit as dead as her brothers had been the moment she’d pushed in the knife. The horror of it only grew stronger, refusing to fade away. But what had she expected? To be at peace?

The glider had begun to rotate slowly; she’d thrown more powerfully with one arm than the other. Tvíbura came into view, still far from the zenith. She looked away, up at the underside of the glider as the sunlight fell on the panels. On each one, she’d written the same words, repeated half a dozen times. She read and re-read the message, clinging to it as the glider turned, until she saw dusk begin to creep across the limb of Tvíburi. Her home world hadn’t let her escape; it was pulling her back to the east.

Rosalind reached up and gripped the handle bars, trying to stop herself from shaking so she could gather her thoughts and strengthen her resolve. She was not an inert piece of cargo; she still needed to do her best to keep the glider stable as she came into Tvíbura’s thin atmosphere, and to steer as close as she could toward a place where the wreckage would be found. The panels would be shredded and scattered across the ice field, but it was up to her to ensure that someone would eventually stumble upon the fragments.

Although we can’t grow the usual crops here, we are well-fed and safe. Do not be afraid to join us if you need to.