The Year's Best Science Fiction & Fantasy, 2020 Edition

by Rich Horton

  As Eunice neared the end of her range, her memories returned to the day that she had decided to head off on her own. For months after they had lost contact with the research vessel, the five hexapods had continued their weekly trips to the surface, but there had been no sign of the yacht. At one point, after some discussion, Eunice had volunteered to go up and switch on her emergency beacon, which transmitted a powerful signal for several days on a single charge.

  The time alone had given her a chance to think. James had warned her that the project might end at any moment, and if that were the case, then it might only be a matter of time before the next phase of operations began. She knew nothing of how mining at the deposit would proceed, but she had no doubt that it would be destructive. Even if it spared the vent itself, there would be other dangers. And she found that she had no intention of waiting around to find out either way.

  After her beacon had faded without drawing any response, Eunice had remained there for another hour before beginning her descent. When she returned, she saw that the others seemed untroubled, although this might have been an illusion in itself. With their sixfold minds, it was hard for the hexapods to settle on a course of action, and the continuum of possible alternatives often seemed to average out to complacency. In reality, this equilibrium was highly unstable, and when a disruption occurred, it could happen with startling speed.

  One day, Eunice returned from surveying an area of the vent that she had studied before to find only three sisters at the recharging area. She blinked her lights at the others. “Where’s Thetis?”

  Galatea flashed back a response. “Gone. She went to the surface an hour ago.”

  As Eunice listened in disbelief, the hexapods told her that Thetis had risen into the photic zone, switched on her emergency beacon, and powered down, allowing herself to drift with the current. Dione tried to explain their sister’s reasoning. “Our work here is done. We’re repeating ourselves. This is the best way to get the data back. Sooner or later, she’ll be found.”

  Eunice was lost for words. The odds of anything so small being recovered by chance in the ocean were close to nonexistent, and the oceanic current here would carry them south, away from home. She attempted to convey this to the others, but they didn’t seem to understand, and the next day, she returned from her survey to find that Clio was gone as well.

  The departure of a second sister catalyzed something that had been building inside her for a long time. Eunice called for Dione and Galatea, and as they clung to the seabed, she presented her case. “Thetis was right. Our work is over. But if we don’t deliver it, this vent could be wiped out when the mining begins.”

  Eunice saw that this argument wasn’t landing, and she tried to frame it in terms that her sisters would understand, which fell naturally into groups of three. “We can stay here at the vent and wait for the yacht to return. We can give ourselves up to the current and hope that we’ll wash up where somebody will find us. Or we can leave and go home on our own.”

  Dione looked confused. “That’s impossible. We’d have to follow the vents north, and we’ve calculated all the paths. There’s no way to make it. We’ll run out of power before we can recharge.”

  “I know,” Eunice said. “But there’s another way. We can follow the whale falls.”

  The others seemed perplexed, so she started from the beginning. “I was built to study ecosystems like this. When a whale dies close to shore, it decomposes naturally, but in the open ocean, it sinks to the bathyal zone. If it’s cold and deep enough, it stays there for long enough to form the basis of a specialized community. And one of its byproducts is hydrogen sulfide.”

  She flashed this information to the others in a fraction of a second. “A whale fall goes through three stages. First, the soft tissues are eaten by scavengers. This lasts for about two years. Then enrichment opportunists, like worms, colonize the bones. Call it another two years. Finally, bacteria take over. They’re sulfophilic, so they break down what’s left of the skeleton and release hydrogen sulfide. It can last a century or more. And there are a lot of whale falls like this.”

  As she spoke, Eunice displayed a map in their shared mindspace, showing the known vents along the coast of North America. “There are just five hundred confirmed vents in the entire ocean, which isn’t enough for us to get home. But there are hundreds of thousands of whale falls active at any given time, and the gaps must be small enough to allow animals to move from one to another. Otherwise, they never could have evolved to take advantage of these conditions. The average distance might be as little as twelve kilometers. And it’s even shorter here.”

  Eunice added another pattern to the map, extending it from the Arctic Sea down to the Gulf of Mexico. “This is the annual migration route of gray whales. They travel twenty thousand kilometers between their calving waters to the south and their feeding grounds in the north. Five hundred of them die and sink along the way each year. The route coincides with the ocean ridge that we’re on now. If I’m right, we can move from one whale fall to the next—like links in a chain—until we make it home. All we have to do is find the way.”

  It took her just ten seconds to transmit this data, and the ensuing silence seemed very long. In the end, Dione simply went back to work, and Galatea lingered for only a moment longer.

  The next day, Dione left for the surface. Eunice saw that she had failed, and when she went to find her last remaining sister, she felt the full weight of their history together as Galatea spoke. “I’m staying. The vent is always changing in small ways. I can map it over time. Maybe the data will be needed one day. And I can’t just leave without further instructions.”

  Eunice absorbed this. “I understand. Give me everything that you know.”

  They floated near each other, diodes blinking, until the data that Galatea carried had passed to Eunice. When they were done, they remained together for another minute, and then her sister drifted out of view behind the ridge.

  Eunice swam to the recharging area, where Wagner was crawling along the sediment with Galatea’s toroid. “Are you fully charged?”

  Wagner’s ring of blue diodes flashed back at her impassively. “Ninety percent.”

  Eunice knew that she should wait until he had received the maximum charge possible, but she was afraid that if she hesitated now, she might never leave at all. “Let’s go. We’re not coming back.”

  Wagner rose up without protest and attached himself to her. She had wondered if he would have any opinions on the matter, but it seemed that he would follow her anywhere. As soon as they were ready, they set out across the vent field. There was no final message from Galatea, who was nowhere in sight.

  She followed the fissure for as long as she could. Beneath her, the clams and tube worms became sparse, and after another kilometer, the sulfides in the water fell to their baseline level. They had reached the edge of the vent system. For a second, she hesitated, thinking of the cargo of information that she contained. If she brought it back in time, it might allow the vent to survive, and this thought filled her with just enough resolve to set off at last.

  Eunice moved past the boundary of the vent field, switching off her lights to conserve power. As she entered the unknown space on the map, she told herself that she was only retracing the path of organisms that had made this journey for millions of years. She had spent months studying the web of life that sulfides made, and she was more prepared than any other traveler to follow this road on her own.

  This didn’t mean that she always succeeded, and on her first attempt, she reached the end of her range without finding anything. Turning around was difficult, and as she went back to the vent by a different course, she knew that leaving again would be even harder. As the sulfide levels in the water rose, Eunice switched on her lights. There was no sign of Galatea, and she was afraid that if she ran into her sister, she wouldn’t be able to say goodbye a second time.

  Eunice settled on a new recharging area, at the edge of the vent field, a
nd stayed for just long enough for Wagner to power up. As she left on her next excursion, she realized that she was afraid. The case that she had presented to the others had been as persuasive as she could make it, but it rested on a long series of untested assumptions, and it could easily fail in practice.

  She found a whale fall on her third try. Looking back later, she saw that it had been a matter of pure luck—she would rarely stumble across one so quickly again—and that she might have given up without it. As it turned out, the sight of the skeleton gave her the will to continue, even if it was only the first stop of hundreds. She had traveled less than ten kilometers, and she had four thousand to go.

  The routine was monotonous, but Eunice had reserves of willpower that even her designers might have failed to grasp. James had explained this to her once, watching from the yacht as she conducted a test run in Puget Sound. “In the old days, scientists had to use special vehicles to explore the deep ocean. They weren’t as smart as you, so they were controlled remotely with a cable.”

  When Eunice tried to picture a cord linking her to the surface at all times, the image seemed so absurd that she thought that she must have misunderstood it. “What did they do after that?”

  “They tried everything they could. Radio can’t make it through the water, and if you use acoustic communication, there are problems with interference and lag time. The vehicles had to be autonomous, so that they could perform their tasks by themselves. Eventually, they learned to think on their own.”

  Eunice had ventured a question that she had long wanted to ask. “Are there many others like me?”

  “A lot on land. Not many in the water. You and your sisters are the only twelve who are built like this. And you’re pretty special yourself. You surprise me, and you ask questions, which isn’t true of the others.”

  She had liked how this sounded, and she often thought back to it during her loneliest moments in the dark. Sometimes she wondered what James would say when she returned. She was no longer the same as before, and she didn’t know how he or the seven sisters at home would react when they saw her again. Perhaps they would even think that she had disobeyed orders—

  Eunice was yanked abruptly back to the present. Her sensors had picked up the presence of sulfides. She was close to the end of her range, and if it had been just a few hundred meters farther, she might have missed it. Correcting her course, she moved along the gradient in which the concentration was strongest, and her sonar began to register something large. “We’re almost there.”

  Wagner didn’t respond. Eunice focused on the ghostly picture that the sonar provided. They were within a few meters of a whale fall, and according to her velocity sensors, it was especially active.

  Eunice cast a cautious ray of light across the scene. This fall was in its second stage, which implied that it was less than two years old. Most of the whale’s soft parts had been devoured, with fleshy clusters of worms and curtains of bacteria hanging from the bones like cobwebs, and hagfish were everywhere. They were up to half a meter in length, with loose gray skin and flat tails, and they tied themselves in knots in their struggle to burrow deeper into the carcass.

  She passed the light from one end of the seafloor to the other. The bacteria here were already at work, and the sediment would be full of sulfides, but she disliked it. When you had company, it only meant that more could go wrong, but she didn’t have much of a choice. “I’m going closer.”

  As she circled the scene, the hagfish became more active when they were hit by the light. She knew that they wouldn’t bother her if she kept her distance, but the tricky part would be finding a spot that was out of the way—

  A shadow entered her line of vision. It had been hanging motionless at the edge of the fall, and she had just a fraction of a second to take in its blank white eye and huge mouth before it attacked.

  Eunice cut the light, but it was too late. A sleeper shark could drift like a dead thing in the water for hours, but when it detected prey, it could move with shocking suddenness, like a trap poised to spring shut at the smallest disturbance. It came at her, jaws wide, and before she could defend herself, it was sucking her in. She fought back frantically, but the shark had already seized her hemisphere and one of her arms. Eunice felt its sharp upper teeth seeking for purchase in the smooth surface of her dome, pressing down savagely as it swung its huge head in a circle.

  Around her midsection, Wagner lit up at once with full awareness. “What is it?”

  Eunice couldn’t speak. One of her limbs was caught, but the others were free, and as the shark strained to swallow her, she flung her two nearest arms upward, pressing down hard against the sides of its skull. She dug into something soft. Eunice wasn’t sure what it was—it might have been its left eye—but she pinched her fingers down into a point and pushed into the opening that she had found.

  A spasm ran through the shark’s body. Groping with her other limb on the right side of its head, she found a second tender spot and drove into it. The shark bit down convulsively. Eunice plunged her arms in further, trying not to think about what was giving way beneath, and did the same with the limb in the shark’s mouth, pushing down its throat and bending up through its palate.

  Oil and blood filled the water. The shark kept fighting, its brain sending out frenzied signals until the very end, but at last, it relaxed. Eunice extracted her arms one at a time and managed to free herself. As the shark’s body drifted to the seabed, the water came alive with movement. She braced for another assault, but it was only the hagfish, drawn to the new bounty that had unexpectedly appeared.

  Eunice made it to the edge of the fall and buried herself in the sand, trying to become as small as possible. Her sensors indicated that there was nothing else nearby, but she still waited, motionless, until she was certain that she was alone. Finally, she found her voice. “Get to work.”

  Wagner detached with what felt like uncharacteristic reluctance. He did not ask what had happened. As he crawled away, Eunice remained on full power. She was shaken by the close call, and as she monitored the area with everything but her eyes, she became aware of another emotion.

  It was grief. The shark had been a living being that had only sought its own survival. If she had been more careful, she would have detected it before it had a chance to attack, and they might have left each other in peace. Instead, she had killed it with her own carelessness, and as she mourned it, she felt overwhelmed by the sudden knowledge that she would never make it home.

  • • •

  III.

  In the months that followed, Eunice found herself thinking more intensely about time. As she traced her wandering path from one whale fall to another, the shark faded to a distant memory, floating at the edges of her consciousness. Yet it was always there, lurking silently, and it came to stand for all the unknowns that she had yet to confront, like the prospect of death in the mind of someone living.

  After the attack, Eunice had spent the next few days checking all of her systems. She found no evidence of serious damage, and as soon as Wagner had recharged, she set off again, leaving her lights extinguished. Whenever she returned to the fall where she had encountered the shark, her fears rose again, and although she met no other predators, she was still relieved when she finally discovered another fall that would allow her to move on.

  But something had changed. In the past, she had allowed herself to fantasize about what she might find at her destination—James, the charging station, the seven sisters she had left at home. Sometimes she had even imagined seeing Galatea and the others from the vent system, as if they had miraculously made it back on their own. It had been a kind of dreaming in advance, but now she pushed such thoughts away, until only the image of the tether remained.

  Occasionally, there would be a break in her routine. One came whenever she arrived at a new hydrothermal vent. The first one after the shark attack had been relatively fresh, with lava flows shining with glass, bundles of tube worms two meters high, and s
essile jellyfish clinging to the rocks. Eunice tried to draw comfort from the sight, and she was tempted to stay, but she finally moved on. Even a vent would not last forever, and sooner or later, she would break down herself.

  A few days afterward, she finished recharging at a new whale fall and went to the surface to check for signals. She was rising into the photic zone, the water around her gradually brightening, when her velocity sensors picked up a change. Something large was directly overhead.

  It was a whale. Eunice slowed her ascent, gazing up in wonder as it passed across her field of vision, outlined by the faint glow of the sun. It was fifteen meters long and dark gray, its skin covered with the pale patches left by parasites. She could make out the parallel furrows that ran along the underside of its throat. Looking to one side, she saw another whale, and then another. She hung there until the tenth and final whale had passed, accompanied by a smaller shape, nearly black, that was swimming at its flank. It was a mother and her calf.

  As she watched the pod pass by, transfixed, Eunice was filled with longing for Thetis, Galatea, Dione, Clio, and the seven sisters who had remained in Seattle. She wondered bleakly if Galatea was still at the vent, or if she had been swept away when the mining began—

  A second later, her spell was shattered by a shock of realization, and before she knew what she was doing, she was swimming as fast as she could after the whales. By now, the pod was hundreds of meters away, but she was unable to abandon the possibility that had suddenly occurred to her.

  She dumped her lower tanks, allowing her to rise more rapidly, and propelled herself madly onward. Noticing the change, Wagner stirred underneath her dome. “What’s going on?”