She was nearly there. Forcing herself to her limits, she gave everything that she had to one final push—
—and failed. The pod was faster than she was, and the idea had come to her too late. Eunice surfaced, her six eyes searching in all directions. The sun was high in the sky, but she saw nothing but empty ocean.
As Eunice looked in the direction that the pod had gone, one of the whales sounded. A white plume appeared above the water, followed by its broad back, and she caught a glimpse of the paired flukes of its tail before the ocean closed over it again. She managed to mark the path along which it was moving. If this was their migration route, it would be a promising line to follow, as countless whales gave their bodies to its invisible shadow under the waves.
Eunice added this to her store of data and sank down. If riding a living whale would be denied to her, she thought, she would travel on the backs of the dead. Every language had its own word for the ocean, and in one ancient tongue, she recalled from her lessons, it had been called the whale road.
Days and weeks passed, and there were times when the way forward felt endless. Yet there was no denying that she was getting closer. Occasionally, Eunice allowed herself to feel hopeful—and then one last complication made her wonder if she had been deceiving herself all along.
It happened when she was retracing her steps to another whale fall. Eunice was still five kilometers away when she found herself faltering. At first, she thought that it was her imagination, but as she continued to slow, she realized that there was no denying it. She was running out of energy, long before she should have reached the end of her range, and if she failed now, she would never make it back.
In the end, she was saved by a stroke of luck. She was moving south, on the return leg of an excursion, which gave her another way to cover the remaining distance. Adjusting her buoyancy, she rose from her usual position near the seabed. At this level, she would be unable to detect any new falls, but this was less important than returning to the one that she knew was there.
When Eunice was three hundred meters from the surface, she felt the oceanic current, which was sweeping its way south. She powered down, retaining only her navigational systems and the bare minimum of maneuverability, and allowed herself to drift this way for four kilometers. As soon as dead reckoning told her that she was near the last known fall, she descended.
Eunice made it back with almost nothing to spare. As Wagner went to work, she anchored herself and pondered this new development. It had been only a matter of time before she experienced a breakdown, but this was less a straightforward malfunction than a reduction of capacity. She had been feeling tired in recent days, which she had chalked up to a combination of nervousness and uncertainty, but now she had to acknowledge that her range had indeed fallen.
There were several possible explanations, none of which was pleasant to contemplate. She suspected that a battery issue was to blame—by now, her power banks had been depleted and recharged hundreds of times—but it might also be a combination of factors. Wagner’s fuel cells could have suffered a loss of efficiency, and it might even be the result of the shark attack, which could have caused unseen damage that had become evident only now.
Eunice ran a series of diagnostics, which uncovered nothing useful. All that remained was to quantify the problem. Once Wagner had recharged, instead of setting out in search of another whale fall, she conducted a test, moving in a tight circle around her present location until her power faded. It took less than forty laps. Checking the distance that she had covered, she found that her range had fallen from thirty kilometers to around twenty-five.
The numbers were unforgiving. Based on her own data, the average distance between whale falls in this part of the ocean was ten kilometers. If her range fell much further, she would no longer be able to cover that distance without the risk of failure. The calculus of survival, which had always been unfavorable, had grown worse. Now every trip would be an even greater gamble.
It left her with a hard choice. If her range was reduced below twenty kilometers, or if she was stranded between falls, she would have no choice but to stop. She would keep going until she could travel no farther, and then she would float to the surface, switch on her emergency beacon, and power down, hoping that someone would find her before this last transmission died.
She shared none of this with Wagner, who grew even more silent, as if conserving his strength for the challenges to come. They were almost home, but now her progress became inexorably slower, tracing a curve that approached but might never reach its goal. She tried to focus instead on each step, and she managed for a while to put the map out of her mind.
One day, Eunice came across a whale fall that was different than the others. Looking for a resting spot along its spinal column, she noticed that hoops of some stiff material had been attached to its rib cage, and it took her only a second to realize that they were artificial.
Wagner seemed surprised that she hadn’t issued her usual instructions. “What is it?”
“Hold on.” Eunice tried to think. The hoops were made of metal, which had oxidized into red heaps of rust. Occasionally, she had found carcasses skewered with harpoons, but this was something else.
The answer gradually came to her. These metal hoops were ballast, and the whale had been sunk here deliberately. It was an experimental whale fall. Because natural falls were hard to find in the open ocean, she recalled, scientists had sunk carcasses on purpose to study them over time. It meant that human beings had been here before her, and that she was close to civilization.
According to her map, she was still a long way from home, but she was unable to resist taking a look. After Wagner had powered up, Eunice rose to the surface. They were far from land, and there was no sign of human activity, but when she turned on her radio, it was with an unusual degree of anticipation. She remembered how it sounded close to shore—she often heard noise from other sources, even if nothing was directly transmitting to her—and now she listened to it anxiously.
There was nothing there, but she felt her hopes rise. It had been so long since she had seen any trace of humanity that even this vestige of it, long since abandoned, seemed like a message. For the first time in weeks, she allowed herself to think that she might make it, and as she descended again, she realized that she had been waiting for a sign without knowing it.
Finally, on a day like any other, she arrived at her last whale fall. Checking her position, she found that she was thirty kilometers from home. Nothing was visible up top—the shore was just over the horizon—and her radio was still out of range. But there was no question that she was close.
Returning to the whale fall, Eunice forced herself to proceed carefully. Now that her destination was only a stone’s throw away, she wanted to go for it at once, but she knew that she had to be more careful than ever. There would be no more falls where she could rest. In shallow waters, a carcass would float, not sink, which meant that this was as far as she would get on the whale road.
After Wagner had attached himself again, they left the fall and headed east. Eunice allowed herself to look back once at the warren of fallen bones, knowing that she might never see one again, and then she turned to face what was coming. The rules of the game had changed. She had thirty kilometers to cover and an effective range of around twenty-five, so she had to draw on all of her available resources, which came down to herself and the current.