On a wide and wondering world in a wide and wondering galaxy, there lived a mermaid. She was not the only mermaid who dwelled in the deep and dreaming oceans of her world. An entire society of mers shared rule of the seas with the whale-sages and the anemone-councils, among many others. This particular mermaid had named herself Essarala, which means seeks the stars in the language of tide and foam.

Essarala’s mothers and sisters and cousins understood the significance of her name, and they sometimes came to discuss it with her. On one such occasion, Essarala sat upon a rock jutting out from the sea, the waves lapping against her koi-spotted tail. It was nighttime, and she gazed longingly up at the constellations and the one bright planet that was visible to the naked eye. The stars in those constellations, she knew, were suns like the one her own planet orbited, a fact that fascinated her but which none of her relatives found of particular interest.

“We are navigators true and fierce,” said one of her younger sisters, whose name, Kiovasa, meant the sea and the moon are partners—a standard, conventional name, resurrected every few generations by proper-thinking mers. She swam in lazy circles around Essarala’s rock, her striped tail flicking in and out of the waters. “But I fear, Essarala, that you mean something other than simple navigation.”

“I want to visit the stars,” Essarala said. “There are other worlds out there. Why remain confined to this one, when I could see the plethora of galaxies that exist?”

Kiovasa playfully splashed water at her. Essarala accepted the drenching with good humor. After all, she had nothing to fear from water.

“I don’t think it’s about wealth, for you,” Kiovasa said. “If all you wanted were riches, why, we could find you plenty of plunder.”

Essarala had to admit this was true. The sailors who plied the waters made copious offerings to the sea, either in exchange for good luck or, more tragically, when their ships sank and their cargoes spilled into the ocean. From the moment of her birth onward, Essarala’s family had not stinted with their gifts, and when she grew older and more adventurous, she, too, had participated in scavenging expeditions so she could give gifts back in her turn. Her own sea-cave was filled with asymmetrical crowns set with spinels and sapphires, gilt-edged chanfrons, scrimshaw depicting sacrifices to eldritch gods, and more.

But these gifts, however well-intentioned and however gratefully received, did nothing to ease the itching in Essarala’s heart whenever she looked up at the star-wealth of the night sky.

Kiovasa spoke with Essarala a little longer and found that Essarala would not be dissuaded from her desire. Having established that, Kiovasa called out a song of farewell and dived deep, swam fast, leaving Essarala behind.

Essarala might have remained suspended in the land of dreams forever, coming to her rock on clear nights to gaze fruitlessly skyward, if not for the arrival of the traders.

The traders came from the sky in a great ship made of metal. It did not look like the galleons or junks or outrigger canoes that the mers were familiar with. But then, mers had little expertise in shipbuilding, so this did not alarm them unduly.

The ship landed on the coast of an island above the coral reef where Essarala’s family held their ancestral seat. From it emerged creatures the likes of which the mers had never seen before either; no two of them alike. Some of them walked on two legs and some on six, some of them had six fingers on their hands and some had tentacles instead, some of them had friendly waving eyestalks and others no eyes at all.

The mers’ interpreters worked day and night to communicate with these newcomers and find out what they wanted. Their visitors cooperated with this process, making offerings of shimmering metalweave fabrics and curious tools for capturing fish more efficiently. The mers found the former of more interest and smilingly declined the latter. After all, they had treaties with the fish nations and no desire to overstep them.

Essarala learned of the traders from her cousins’ gossip, and she lingered near the interpreters, watching and wishing. She longed to explore their ship and ask them to take her with them to the stars. But the more she listened, the more she learned, and one thing became obvious: their ship might carry water for its crew to drink, but it didn’t contain water for a mer to live in. Saddened by this obstacle, she withdrew, and at first no one noticed it.

In the meantime, the mers and visitors learned to speak to each other. They planned a grand feast, featuring the fish nations’ best offerings, as well as tasty morsels of sea urchin or sea cucumber and the finest kelp salads. The visitors, for their part, ran curious tests—to make sure they didn’t accidentally poison anyone, they said—and contributed strange delectations of their own, some resembling fruit, some resembling fish, and some concoctions that the mers had no word for other than delicious.

At last Kiovasa realized that she hadn’t seen Essarala hanging around the traders for some time. Concerned, she secured her sister an invitation to the feast. It wasn’t hard—no one would have thought of leaving her out—but Kiovasa made sure it had been handwritten upon a sheet of magical ice by one of the mers’ master calligraphers, all the better to reignite Essarala’s interest.

Kiovasa found Essarala on her rock as usual. The weather had been unusually fine, courtesy of the local dragon-spirit, yet Essarala had hardly interacted with her family at all during the past week. Still, she couldn’t refuse to welcome her sister.

Kiovasa presented the glittering invitation to her. “Come,” she said coaxingly, “you’ll hear more stories from the far-travelers, of the places they’ve seen and the things they’ve eaten. They’ve even brought foods from the stars.”

Essarala didn’t react with the delight that Kiovasa had expected. “Sister-sweet,” she said, turning the invitation around disconsolately in her hands, “I have heard their stories. What’s more, I have been listening to the murmurs of the waves and the wind about this ship of metal, and they have confirmed what I thought. This ship of metal is full of travelers from the stars, yes—but the ship itself has no water for a mer to live in.”

Kiovasa, who had been swimming clockwise around the rock, reversed direction, thinking. Her sister was right. All of the traders were land-dwellers.

“You should come anyway,” Kiovasa said. “At least you’ll get a glimpse of the faraway worlds that you’ve always loved.”

“No,” Essarala said, turning her face away. “I’m afraid that once I hear more stories, being left behind when the visitors leave—and they will leave, won’t they?—will be all the more unbearable.”

It was a young mer’s logic. But the only cure for that was time, and time was what they had so little of. “In that case,” Kiovasa said, “we must take more drastic measures. We must visit the witch beneath the waves, and she will have a solution.”

The witch beneath the waves lived at the bottom of a great chasm, one so vast and dark that even the mers visited it reluctantly. Swarms of lanternfish lit the way down to the witch’s dwelling, and even so, Kiovasa and Essarala struggled to see anything in the murky gloom of the waters.

At last they reached the witch’s dwelling. Strange phosphorescent worms and rocks indicated the entrance. “We have come to ask a boon of you,” Kiovasa called out, her voice distorted by the pressure of the waters.

For a long time all they heard was silence. And then the witch’s voice emerged from within: “I would hear from the one who wishes the boon.”

Essarala let go of her sister’s hand and swam toward the voice. She could not see the witch, and it made her afraid. “It’s me,” she said, almost in a whisper. “I wish to petition the travelers from the stars and ask to join their crew.”

A soft glow lit the witch’s dwelling from within, more worms waking and wriggling. The witch herself, however, only manifested as a sketch of inky lines, like half a silhouette. She was smiling, but her smile was sad.

“You would give up the sea you know, and your family, and the songs of gulls, to explore the worlds beyond?” the witch asked.

“I don’t think it’s such an evil thing,” Essarala replied, “to want to see new worlds and taste their waters.”

“Evil, no,” the witch said. “Difficult, yes.”

“If you can’t help me—”

“That’s not the kind of difficulty I meant,” the witch said. “I can give you two legs like the humans, that you might walk on land, or upon the deck of a starfaring ship for that matter. The rest, though—the rest is up to you. For there’s more to starfaring than having legs. You’ll have to familiarize yourself with their alerts, read oxygen gauges, watch out for toxic atmospheres and flesh-eating pathogens, and that’s just the beginning.

“You are well-educated in the ways of your people,” the witch went on. “I have no doubt that you can identify every fish in the sea by the way it swims, and the birds of the waters by their silhouettes. You know the language of the moon when she sings to the waters and how to read the writing of every civilization that has ever built ships. You can read the wind and the waves. But where you are going, it’s darker even than the chasm I call home, and there’s no wind in space, nor waves other than the spiral density waves of the great galaxies themselves.”

Essarala trembled, for while she didn’t understand much of the terminology that the witch had used, she recognized that she was out of her depth. If only she had spent some of that time star-gazing instead learning about the strange and chancy technologies that land-dwellers had invented, and which might keep them alive in the hostile void. But it was too late now. She had to choose, and choose soon, for the traders would not remain indefinitely.

“Tell me your price,” Essarala said, speaking more loudly.

The witch nodded. “Someday you will want to come back home,” she said. “When you do, visit me, and we will speak of it then.”

“Is there nothing else you would accept of me?” Essarala asked, for the thought of returning to the chasm filled her with a nameless dread.

“That is the price,” the witch said. “Take it or leave it.”

“I will come with you,” Kiovasa said to Essarala, “when you return. You won’t have to do it alone.”

Much later, Essarala would remember the witch’s expression and the grief in it. At the time, however, all she knew was her gratitude for her sister’s kindness and loyalty. She reached out and pressed Kiovasa’s hand.

“I cannot do it here,” the witch said. “The depths would kill you before you could ask your boon of the spacefarers. But I can give you the means.”

The dark lines of the witch’s figure shifted and stirred. For a moment she resembled nothing so much as the abstract patterns that moonlight makes over the waves, except in reverse. Then the patterns reassembled, and the witch held out a knife, hilt-first.

It was made of shell, and in the eerie light of the worms and rocks it had an iridescent sheen. “It will hurt,” the witch said. “Certain kinds of desire always do. When you are ready, cut your tail in half, and your legs will emerge. If you change your mind”—and Essarala opened her mouth to protest that she wouldn’t, except the witch’s stern look quelled her—”then throw it into the sea, and it will find its way back to me.”

“Thank you,” Essarala said in spite of her trepidation, for a favor given must always be acknowledged. She did not speak the rebellious thought in her heart: that she would journey among the stars as long as possible, and perhaps in that time she would find a way to cheat the witch of her price.

The next night, Kiovasa and Essarala attended the feast. The sentinel sharks and dolphins recognized their invitations and let them in without comment. On any other occasion, the two of them would have noticed the splendid decorations that the creatures of sea and shore had labored over. Bright banners of fabric woven from hippocampus manes and the mers’ own long tresses waved in the wind; lanterns containing glowing fungus and dancing fireflies illuminated the long tables. The platters, of lacquer or beaten gold, carved jade or peerless celadon, contained every form of delicacy the peoples of the sea and the peoples of the stars knew how to prepare.

But Kiovasa could only think of how she was going to lose her sister, and Essarala felt the weight of the witch’s shell knife, carried in a pouch of gold-washed chainmail, as though it would drown her.

“Come join us!” the other mers called from their seats by the lapping waves. They were already drinking and singing, exchanging stories of navigators and mapmakers, and the occasional ballad of island-dwelling lovers. Kiovasa waved back, heavy of heart though she was.

“I must do it now,” Essarala whispered to her sister, “or I will lose all courage.” For beyond her many relatives she could see the visitors from the stars, supping in their various fashions, and even past them, the long silhouette of their far-voyaging starship. And the longing burned even more fiercely in her heart.

Mers have little notion of privacy, since everything that happens in the sea is known to one and all in short order. Even so, Kiovasa nodded and took her aside, a little way down the shore from the feast. Gulls and terns wheeled overhead, and the sandpipers cried out, whether in warning or welcome. No one watched, and why should they? They had other matters on their mind.

Essarala drew out the knife and passed the pouch over to her sister. She steadied herself with a deep breath, tasting the salt spray in the air, the sweet ether influence of the star-currents. Then she brought the knife plunging down.

The pain of the cut almost caused her to faint. But her sister caught her in her arms and steadied her as she swayed. The beautiful koi-spotted scales of Essarala’s tail peeled away, and she emerged with two legs, like the humans of her world.

Kiovasa kissed her on the brow. “Go,” she said to Essarala. “The stars are waiting for you.” And she watched from the shallow lapping waters as Essarala took her first uncertain steps.

One by one the mers noticed; one by one the traders noticed. And they all stared, murmuring in wonder among themselves, as Essarala made her way to the starship’s captain.

The captain dined at the head of the aliens’ table. They were a tall creature covered with downy feathers, and their head sported a magnificent crest that Essarala had originally mistaken for a hat. When they saw Essarala approaching, they nodded at her in welcome. “Have you had a chance to enjoy the food?” they asked her in her own language.

For her part, Essarala was embarrassed that she could not speak the captain’s tongue, although she knew very well that it contained sounds that no mer could make. “My name is Essarala,” she said, “and like my name, I wish to seek the stars. I beg a boon of you—that I may join your crew, and travel to distant worlds with you.”

The captain glanced at the koi-colored scales that clung still to Essarala’s bare legs and knew the sacrifice that she had made. “Of course you may,” they said kindly. “But you will start as the least among my crew, not because we wish to insult you, but because there are a great many protocols involved in life on a starship that you will have to learn before you can be trusted with more.”

“I do not mind,” Essarala said, her heart leaping within her.

“You will,” the captain said, “but no matter; you will also have friends and comrades to share the journey with you.”

And with that they invited her to squeeze in to their right, and to join with them in the feast.

The next morning, the captain and their crew prepared to say farewell to the mers and the people of the sea. Essarala, however delighted with her good fortune, was not so overcome that she forgot her sister. She sought Kiovasa out by the ocean’s edge and ran out into the water to embrace her one last time.

“I hope you see every world around every star,” Kiovasa whispered into her ear. Kiovasa, who had never thought much about the sky except the fact that her sister yearned after it so much, had no idea how many worlds there were in the universe, or stars either. But Essarala accepted the blessing in the spirit in which it had been given.

“I will sing your name to each of them,” Essarala promised.

“I will listen for it every night,” Kiovasa said. Then she shoved Essarala lightly. “Go! I don’t want you to miss your opportunity.”

Trepidation seized Essarala’s heart, but she had come too far to turn back now. She ran through the splashing waves to the starship, which gleamed pink and orange and silver-bright in the sunrise. Already she was acclimating to her new legs, and to the sensation of her feet in the wet sand, and then on the cold metal of the starship’s ramp.

The captain welcomed her aboard and introduced her to the crew members who would show her the basics of life on a starship. “Listen always to Ssen,” the captain said, indicating a snakish alien whose mechanical suit provided them with tentacle-like grippers in the place of hands. “They will watch over you. I will see you at ship’s mess.” And the captain dismissed her.

“Come with me,” Ssen said through a translation device. They showed Essarala how to strap herself into a couch for liftoff and warned her not to panic when the couch engulfed her with oxygenated gel to cushion her from the ship’s acceleration. “As a member of the crew,” they added, “you will have to study the fundamentals of physics, and the functioning of the ship, and how to help with its maintenance. We’ll speak more of that after we’re underway.”

As a kindness to her, although Essarala would not realize it until later, Ssen had given her a couch across from the viewport that would give her the best view of her world as she left it for the first time. Her heart beating rapidly with mixed worry and excitement, Essarala braced herself for liftoff. Ssen need not have been concerned about her reaction to the protective gel, for it was not so different from the waters she had swum in all her life.

Nevertheless, while Essarala’s innate magic as a mer protected her from the crushing depths of the sea, and the variances in pressure, it gave her no such defense from a starship’s acceleration. As the starship blasted off for a destination whose name she didn’t know, she caught only the merest glimpse of her native ocean from above, and the glittering of sunlight on the waters, before she lost consciousness.

Ssen apologized profusely once they had safely left the world’s gravity well. “I should have expected that you would need more protection,” they said, “and prepared your couch accordingly. I will teach you how to do that yourself, so this incident is not repeated in the future.”

It wasn’t the only thing Ssen showed her. Essarala learned that Ssen usually took on the task of training new crew, partly because they had infinite patience, but partly because they never slept and could remain vigilant for the inevitable mistakes. She had cause to be glad of both traits, for she always had someone to listen when she despaired of achieving basic competence in her assigned tasks, and Ssen ensured that she would never put the ship in danger.

From Ssen she learned that the ship had two propulsion systems, one used for short distances and landing on and departing from planets or starbases, and a fancier one that enabled it to travel near the speed of light. “The latter is the domain of the engineer-priests,” Ssen told her, “and unless you choose to become initiated in their mysteries, it will be of no particular concern to you. But you will need to study orbital mechanics, for everyone’s safety.”

Over the passing days, weeks, months, Essarala grew proficient in putting on the spacesuit that Ssen designed for her and produced using the ship’s matter spinner. She only once forgot to check the oxygen tank, which Ssen lectured her gently about because it was a serious matter. As she grew in proficiency with the ship’s systems and the simple maintenance tasks that Ssen assigned to her, she started taking pride in her work, however simple. She started to sing at her work, songs of the sea to remind her of the home she’d left behind.

In her leisure hours, she sat by the viewports of the starship and gazed at the stars streaking by. She saw wonders up close, from the dust-forges where stars are born to the hot glow of the accretion disks around black holes. She saw planets of different colors spinning like enchanted beads, and their diadems of moons. And all these visions reminded her of her sister Kiovasa, who had helped her attain her heart’s desire, and the fact that they were now parted; but she was not sorry, not yet.

Next the starship visited a starbase to restock on supplies. While Essarala wasn’t present for the negotiations, given her lack of expertise, she helped Ssen stow the supplies in the ship’s hold. Despite the labor involved, she enjoyed figuring out how to fit the containers most efficiently into the available space. In the sea, she’d never had to worry about space before, but it was, of course, an ongoing concern in the confines of the ship.

Afterwards, the captain gave the two of them permission to explore the station while the ship was docked. “You don’t mind my following you?” Essarala asked Ssen, for she wondered if they wanted some time to themself.

“No one should have to brave a starbase alone on their first visit,” Ssen said. “Of course I don’t mind.” And they took Essarala to the starbase’s zero-gravity gardens with their fantastic floating plants and intoxicatingly perfumed flowers, and clusters of lanterns that changed color according to the designer’s whimsy. After that, Ssen introduced her to other pleasures, from restaurants that served crisp honeyed insects to lounges where people traded poetry new and ancient, from cafes where one could pet small furry aliens who told one’s fortune to monuments where spacers carved the names of those who had been lost to pirates, or radiation, or other hazards.

Not least of all, Ssen took her to the observation deck of the starbase, where Essarala caught her breath at the sight of the stars all around them, as though everyone lived inside a constellation of splendors. Ssen told her the names of the brightest stars and the peoples who lived on their worlds and visits they had made in times past.

At the end of these journeys, Ssen took Essarala aside in a quiet lounge, their expression serious. Essarala shivered with dread, for she feared that she’d performed so poorly aboard the ship that they were going to abandon her here. But Ssen hissed in concern when they smelled her fear and bought her a soothing cup of broth.

“If you ever weary of life on our ship,” Ssen said, “we will find you a new home, or return you to your old one. This starbase, for instance. It’s known for its hospitality, and you could make a life here if you chose, not just with the skills you’ve learned with us, but with your singing.”

Essarala knew she had a fine voice, like every mer. She hadn’t realized that Ssen had listened to her singing during her chores. “Do you wish for me to leave?” she asked in a small voice after taking a sip of broth.

“Not at all,” Ssen said, their voice softening. “But you should always live on a ship because you’re there by choice, not because you’re out of options.”

“I love the ship,” Essarala said. It was true. She loved its metal sleekness and the way it hummed when it accelerated or decelerated. She loved the views of whorled nebulae and globular clusters. She loved the starbase, too, with its vast exterior symmetries and asymmetries; the way it housed a variety of aliens even more diverse than those upon the ship. She could not imagine giving up her shipboard life, not yet.

And if she dreamt sometimes of her sister’s kind smile, and the sea’s embrace, and the moving constellations of glowing jellyfish or the whale-sages’ vast chorales as they deliberated upon matters judicial, or what it had been like before she’d given up her koi-spotted tail to walk upon two legs—why, that was the price she had to pay, in exchange for this bounty.

In the years to come, Essarala grew expert in the ways of life upon a ship, until she almost forgot what it had been like to live upon a single planet and no more. The starship visited other starbases, each more wondrous than the last, and paid calls to other worlds as well. By now, Essarala herself helped Ssen orient the ship’s newcomers and occasional guests, and she took great pleasure in sharing her hard-earned knowledge.

Now at mess she knew all the crew by name, and the captain nodded to her in greeting when they passed each other. She knew the astrogator and her fondness for fruit preserves, and the engineer-priests with their incantations and calculations. She knew the ship’s pilot, the gunner who defended them against pirates, the cook. And they in their turn knew her, and sometimes, in moments of leisure, asked her to sing the songs of her world for them.

Essarala learned to fly in skysuits in vast and turbulent gas planets, some of which had corrosive atmospheres. She saw twin sunsets over methane seas and meteor showers flung across brilliantine nighttime skies. She walked through forests of towering trees sharded through with crystal and breathed in the fragrance of flowers that bloomed only once a millennium. And she kept her promise, too: for every world she visited, she sang her sister’s name.

Someday I will go back and tell her of the things I have seen, Essarala thought again and again. But not yet, not yet.

But Ssen was not done teaching her, as expert as she had become in the starfarer’s life. Now that Essarala had mastered the pragmatic skills she needed to survive, and to contribute to the crew, Ssen sat with her during their spare hours and taught her theory. They started with the simplest principles of mechanics and chemistry, then progressed to special relativity.

And it was in learning about relativity that Essarala finally understood the price that the witch beneath the waves had exacted from her—or, more accurately, warned her about.

She looked at the equations, at the time dilation factor that had emerged from such deceptively simple premises: the constant speed of light, the fact that no inertial frame of reference was privileged over any other. In the years that she had spent away from home, decades upon decades had passed for her sister Kiovasa. And mers lived long, but they were not—quite—immortal.

Ssen saw Essarala clench her hands in distress and asked why.

“I must return to my homeworld,” Essarala said. “However long it takes—but sooner is better. For I left unfinished business there, and I did not realize it until now.”

“It is out of our way,” Ssen said, “but we can petition the captain. Even if we cannot take you there, we may be able to find another ship that can.”

Indeed, the captain summoned Essarala to their stateroom. They listened attentively as Essarala explained her dilemma. “I will do whatever it takes to get back home,” she said. She feared it was already too late—but that, she would not say aloud, even to the captain who had so generously welcomed her to their crew.

“It’s true that it’s a long way for us,” the captain said. “But we will make the detour, and we will wait as long as you need. I know what it’s like to be far from family.”

Essarala bowed her head. “You won’t need to wait,” she said. “I will not be leaving my home again. Thank you. This is a kindness I cannot repay.”

The captain’s crest stirred in the manner that Essarala had learned, by now, meant sympathy. “You are not the only one who gave up a lot in exchange for the long dream of stars,” they said. “We will miss you; but so does your family, I imagine.”

“Thank you,” she said again, and left the captain’s stateroom a little easier of heart.

The captain was as good as their word. They did not head straight back to Essarala’s homeworld, for they had trade contracts and obligations to keep, but they did guide the ship closer and closer to it, in a zigzag path. Essarala pored over the star-maps, dreaming of her return.

One by one, the other members of the crew, whom Essarala had come to think of as friends over the course of her journey, stopped by to give her small gifts. These included fruit preserves from the astrogator (of course), circuit jewelry from the engineer-priests, petrified wood from a certain extinct forest on a certain museum world, and cubes that spindled out performances by radiant holographic puppets. Even the captain gave her a feather from their crest.

Last of all came Ssen, teacher and companion. Ssen gave Essarala a bracelet of star-metal carved with the constellations of the night sky as seen from Essarala’s homeworld during that long-ago visit. “I will think of you,” Ssen said, “even if we never see you again.”

“You have been the best of teachers,” Essarala said, quite overcome. “I will wear this always.”

Ssen smiled their snakish smile, and that was that.

All too soon, for her impatience, Essarala strapped herself into her couch for the landing on her homeworld. This time she didn’t require Ssen’s assistance, and this time she didn’t lose consciousness as the ship decelerated. The world came into view, a whorled marble of blue and green and violet and pearly streaks, and her breath hitched at its splendor; the old made new again.

The ship touched down, and Essarala freed herself from the couch. “I hope it’s not too late,” she said to herself as she and Ssen made their way to the ramp.

“There is only one way to find out,” Ssen replied. “Go, and be well.”

Essarala’s feet met the shore, the same one where the ship had landed on its first voyage to this world. This time she wore a spacer’s suit with its magnetic boots. It had served her well in her time aboard the ship.

She looked over the sea with its ever-crashing waves and the wheeling gulls, then took off the suit. “I won’t be needing this anymore,” she said to Ssen. “You can go ahead and recycle it.”

Then Essarala waded out into the ocean, and as she did, koi-spotted scales grew to cover her legs and feet. With a last shuddering breath, she reclaimed the heritage that she had set aside in exchange for the stars and dived into the waters. As she did, her legs fused into a proper mer’s tail.

Essarala hadn’t forgotten her promise to the witch, and besides, the witch might know where—if anywhere—to find her sister. So she swam deep, beyond the colorful coral reefs with their shy darting fishes, beyond the pods of dolphins, until she found the lanternfish that lit the way to the witch’s dwelling. The sea was cold and dark, but it was, after all, no colder and no darker than space.

“I have returned,” Essarala called out, wondering what she would do if the witch had perished in the interim.

But witches are not so easily escaped. The worms began to glow, as they had all those years ago, and the witch of the waves emerged. “You have indeed,” she said. This time Essarala could see her face more clearly, and it was not so dissimilar from her own.

“You gave me my heart’s desire,” Essarala said. “You said you would name your price once I returned. Well, here I am.”

“Indeed,” the witch said. “I am ready to summon my death. It will take its time coming; but it will come all the same. When it arrives, you will take my place as witch beneath the waves. For you, too, have tasted life among the stars, and you have the wisdom that your journeys have given you.”

It was a hard price, but not an unfair one. “Understood,” Essarala said. “I have a question for you, if you are willing to answer it.”

“Ask.”

Essarala steeled herself for the answer she didn’t want to hear. “What became of my sister Kiovasa? Where can I find her?”

“She is old and ailing,” the witch answered, and Essarala’s heart almost burst with relief. “You will find her by the rock where the two of you spent so many hours gazing at the stars. She has never forgotten you. But you should hurry. She doesn’t have much time left.”

“Thank you,” Essarala said. And then she shot upward through the waters, swimming with all her might toward the rock. It would be terrible if she had come all this way only to be too late after all.

At last she broke the ocean’s surface in an explosion of glittering water and rainbows. “Kiovasa!” she cried when she saw her sister lying upon the rock.

Mers do not age as humans do, but they age nonetheless. Streaks of shell-white had appeared in Kiovasa’s hair, and the stripes of her tail were so faint they were almost invisible. But her face lit when she saw Essarala. “You’ve returned,” she murmured. “You look the same as you did the day you left.”

“It is a magic of the stars,” Essarala said, “which I will explain to you if you wish.” She swam up to the rock and took a seat next to her sister. They hugged each other fiercely. Essarala added, “I will not leave you again.”

“But your dream of traveling among the stars,” Kiovasa said. “I would not take you away from that—”

Essarala grasped Kiovasa’s hands, then craned her neck back to look at the afternoon sky. “You haven’t,” she said.

Kiovasa shook her head, bemused. “I don’t understand.”

“What I did not know before I left,” Essarala said, “is that every planet is traveling through space, and every star, and every galaxy, and more beyond, in a great celestial dance. I wanted to visit other worlds, and so I have. But now that I understand the motions of celestial bodies, I don’t need to leave home in order to journey through the universe.”

“I don’t understand,” Kiovasa said again, “but I look forward to learning, in the time that remains to me.”

for Yune Kyung Lee, best of sisters

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Yoon Ha Lee's short fiction has appeared on Tor.com, in Clarkesworld, and nine times previously in Beneath Ceaseless Skies, including “The Starship and the Temple Cat” in BCS Science-Fantasy Month 4, which was a finalist for the Locus Award and the Sturgeon Award. He is the author of the Machineries of Empire trilogy, and his standalone fantasy Phoenix Extravagant is forthcoming from Solaris Books in June 2020.  Yoon lives in Louisiana with his family and an extremely lazy cat and has not yet been eaten by gators.  Visit him online at www.yoonhalee.com.