That depends. When she stepped onto the tarmac in Irkutsk, the sky crisp and glittering, she was wondering why it had taken her so long to come to Siberia. But earlier, when she boarded the stale plane in Beijing, she was trying not to think about the world’s first marathoner. (You know: the one who died.) And when her husband dropped her at the airport curb in Minneapolis, she was wondering if he’d miss her.

Would he?

He certainly would. They’ve been married eighteen years. Besides: Lately he’s been missing her even when she’s standing right in front of him. Last Sunday, after she’d returned from a fifteen-mile run, she’d been flipping pancakes on the stovetop while he scrolled through headlines on his phone at the counter across from her. There were no more than three feet between them. But when he glanced up and saw a bead of sweat slide past her ear to her chin, her face rosy from the heat of the gas flame, he’d been struck simultaneously by the urge to wipe it away and by the fear that if he tried, he wouldn’t be able to reach her.

What does that mean?

He can’t say, exactly. He knows it sounds strange. How absurd it is to long for a person who is right in front of you! But then he remembered that a colleague had described feeling something like this when she awoke in the night and leaned over the bassinet to gaze at her newborn child. “He was there, but he wasn’t,” she’d tried to explain when she returned to the English department from maternity leave. “I could see him growing up, changing.” She’d set down her tea and picked up a book. “It’s weird, I know. But he disappeared as I was watching.”

What does that mean?

He can’t say, exactly. He doesn’t have a child. All he knows is that he has been missing his wife for months. So when she finally vanished between the sliding glass doors of the airport terminal, his fingers grew cold around the steering wheel and he leaped out of the car and almost (almost!) dashed after her. He wanted to crush the warm weight of her to his chest; he wanted to tug her body back into his orbit and to resume his place in hers. But then the traffic control man began striding toward him with a menacing orange stick, and so he crawled into the Toyota and pulled away from the curb and turned the wheels toward home. With every tick of the odometer, the invisible thread between them tightened and stretched and grew closer to snapping.

Did she feel it, too?

Yes, she did. She does. The ice is violet in this light, perilous and beautiful, and with every step she takes across it, she senses her distance from her husband growing. As she runs, struggling to find her rhythm, she hears the gas bubbling from the bottom of the lake and striking the snow-dusted surface right beneath her slipping feet. At the halfway point she stops for water in a heated tent and sees one runner being treated for the frostbite on his nose. She lifts a hand to touch the tape she wrapped over hers. Another runner, a young man in his mid- twenties, is pale and trembling and asking one of the volunteers, over and over again, what he is doing here. That’s when the pressure in her ribcage grows so fierce that she doubles over. She remembers walking into the airport and easing herself down into a row of vinyl chairs beneath the windows. She remembers watching the Toyota roll out of sight. She remembers bending her head to steady her splintered breathing, her battering heart. What the hell was she trying to prove? At that moment, there was still time. So why didn’t she pick up her luggage and go back home?

Where is home?

Home is a drafty Victorian tilting on red clay bluffs over Lake Superior. The Toyota is parked now on the steep slope of the driveway, its wheels turned in and the emergency brake activated. The curtains are gauzy and the walls are painted indigo, and in the summer the wind whips off the lake and through the windows and the house feels like a moving, breathing thing. Days like that are almost enough to make a person forget about the rotting beams and the crumbling basement with its packed dirt floor that is, quite frankly, terrifying. Anything could be under there. More often than not, it is she who braves the spiders to reach the rattling washing machine. She’s always been more courageous than he. More useful. She can fix a flat tire in under eight minutes. She knows how to build campfires with kindling and flint. There is no reason for him to be worried about her. Right? There is no reason to be worried.

Is he worried?

Of course he’s worried. Only a crazy person wouldn’t be worried. The official marathon website boasts the race as one of the most extreme in the world. Twenty-six miles across the earth’s deepest, coldest freshwater lake. The ice shivering underfoot as hidden hot springs bubble and thunder beneath the surface. The clefts and gaps on the course; the unexpected splits. The snow that can storm down from the Eastern Sayan Mountains without warning, spinning around the runners, slipping beneath their soles, powdering their face masks and obstructing their vision. Sometimes the conditions plummet so quickly that the race is canceled after it’s already started, and the runners have to be tracked down and rounded up in heated tents. He’d researched the marathon for months, the computer screen glowing in his darkened office while his wife dreamed in their oversized bed at the other end of the hallway, and so he knows that two years ago, a strapping young runner from New Zealand collapsed and died only a mile from the finish line. No cause or explanation. His heart simply stopped. “That’s Lake Baikal,” the bearded Siberian organizer had told news cameras with a shrug. Sunlight slanted off the snow behind him, and the wolf fur that ringed the hood of his parka framed his face in spiky shadows. “What can we say? She is tough, she is cold. She does not show mercy.”

“She”?

Yes, he noticed that, too. It’s not uncommon for the locals to refer to the lake as a living being. Some of the runners, he’d read, embrace the shamanistic element by kissing the ice at the starting line or talking to it between increasingly ragged breaths as the miles lurch by and their loneliness swells with their feet. It’s bleak out there, beneath the flat granite sky. Glacial, silent. This isn’t the New York City Marathon, it’s not Boston or Paris or Tokyo, where spectators throng the streets with handmade signs and applaud from the balconies of high-rise apartment buildings. On Lake Baikal, if you want to hear people cheer you on, you’ve got to imagine them. You’ve got to conjure up your own illusions, look for mirages in the crystal fog of your own breath.

What kinds of mirages?

It depends on the runner. Take his wife, for instance: as she continues to drift across the ice, step by ginger step, she dreams of her husband waiting for her at the finish line. A mug of cocoa in his plush down mittens; an apology on his cracked dry lips. To her surprise, she dreams of children waiting, too: trotting on the crusty snow in tiny boots and parkas, waving smudged drawings of the famous Baikal seals.

What children?

Their children. The ones they didn’t have.

Why didn’t they?

Oh, the usual reasons. Money, work. He figured they’d eventually get around to it. Then his parents died. He had that thing with April. In retaliation, she had that thing with Max. And before they knew it, well—he was arranging the tea lights around the living room for her fiftieth birthday party, and the house was filling up with friends bearing books wrapped in tissue paper, and there were trays of catered cheese puffs and rock songs pulsing through the speakers, but there wasn’t a child in sight. He stood in the doorway to the kitchen, watching her slice limes with hands that struck him suddenly, shockingly, as bony and weathered, her hair twisted up into a braid more silver than brown. His heart cracked open with a longing so fierce that he almost didn’t recognize it as his. They had waited too long, he realized. The window had closed.

Who are April and Max?

April and Max are not the point. He doesn’t want to think about them right now. Right now, he only wants the phone to ring. The world outside the kitchen windows is wrapped in the black velvet coat of early morning; the moonlight is spindly and gray, and in the distance he can hear the roiling waves of Superior crashing against ice that lines the shore like a high lace collar. He is squinting at his watch, which he has set to Irkutsk Standard Time. So he knows that currently, on Lake Baikal, it’s four in the afternoon. She’d promised him that she would call as soon as she’d crossed the finish line. The cut-off time for the marathon is six hours. If she hasn’t reached the end by now, something has happened. A twisted ankle, maybe; or a spontaneous snowstorm that has blown the runners off their course. Or maybe she’s gone crazy out there, alone on the ice for hours.

Is that a possibility?

Let’s just say that it wouldn’t be the first time that a fatal combination of sun and ice has confused and beguiled a fragile human in the cold. Plenty of Arctic and Antarctic explorers have perished in pursuit of such a fata morgana. Some locals believe, moreover, that the lake possesses spirits. Powers. On Shamanka Rock, priests used to remove curses. Legend has it that travelers who try to reach Ryty Cape usually die mysterious deaths, and those who succeed in setting foot on the point claim to see creatures from other worlds.

Does she believe this?

No, she doesn’t. She’s a scientist. When she sees the spray of silver bubbles frozen beneath the surface of the lake, she recognizes them not as the breath of some slumbering sea dragon, but as methane gas. Pure and simple. Similarly, the silent turquoise guardians ringing the edge of the far shore at dawn are not monsters or spirits, but ice-encrusted pine trees. And the spindly white trails in the ice, the lines that crosshatch its cold black surface, might look like treasure maps or blueprints to a secret world below, but the truth is that they don’t signify anything and they can’t lead a person anywhere. They’re cracks. Only cracks. She knew that there would be cracks; she knew that the ice would shift and hiss below her. (Still: She didn’t expect the rumbling of the lake to grow louder as she stumbled across the course. And yet: Isn’t it?)

Does he believe this?

He isn’t certain. He’s a poet, after all. He teaches his students that black on a white page can be transformed into something ineffable, transcendent. He believes that meaning is made, not discovered. Myths and legends have origins. Sources.

Is she a poet, too?

No. Generally she doesn’t have the patience for it. But he used to read it to her when she was suffering from migraines. He’d carry her up to bed like a bride (or a child) and he’d lay a cool hand on her forehead and she’d close her eyes and listen to the staccato of his voice and the whisper of pages turning. Sometimes, as she tilted over the towering precipice of sleep, her temple throbbing and her skin burning, she’d think she heard something between the lines: something the poet was reaching for but couldn’t find the words to say. The poem behind the poem. When she woke, she always forgot to ask her husband if this was what he meant by the ineffable. The transcendent. Something you move toward but never quite reach. Something like the finish line of this very race, in fact, which she could see from the starting point but which has not grown any closer over however many hours—three? five?—she’s been out here. It’s simply hovered in the distance—teasing her, flirting with her. Sunshine flags strung on twin poles, rippling over dark blue ice.

Is she going crazy?

Probably not. The bearded Siberian organizer had described this phenomenon the night before the race, while the runners were shoveling forkfuls of lukewarm rigatoni into stomachs taut with anxiety. She was sitting between a runner from Estonia and one from Hong Kong. She’d see them again at the starting line in the morning, hopping on their toes to keep warm, marveling over the indigo cast of the ice. At dinner the windows steamed from the heat of their bodies, and she tugged at the collar of her cable-knit sweater in a futile attempt to cool herself down. What’s strange is that you can see the finish line from the moment you begin, the organizer had said. But no matter how many steps you take, it never seems to grow closer.

What else did the organizer say?

Since it was the fiftieth anniversary of the marathon, he talked about its history. He thanked everyone for coming all this way. And then he made what was supposed to be a surprise announcement: this year would be the final year. These runners were the last runners who would ever race across Lake Baikal. After this, the marathon would be indefinitely suspended.

Was she surprised?

No, she wasn’t. But the others were. She listened to their musical exclamations with an expression as cold and clear as the ice that was shifting outside on the surface of the lake. She knew the ice was withdrawing. She knew that the waters were warming, the diatoms vanishing, the algae invading. She knew that holding the race even now, one more time, was risky. Bold. She guessed that there could already be patches of ice, indistinguishable from the rest, that couldn’t bear a human’s weight. And so she wasn’t surprised, either, when the bearded organizer admitted that some city officials had argued that no one should be racing this year at all. He handed out an extra set of smudged release forms to be signed.

Was she frightened?

On the contrary: She felt invigorated. In the anxious clamor that followed the organizer’s announcement, it was she who stood up and pushed back her chair and assured her fellow runners that they would be fine.

How had she known?

That was their question exactly. The answer: It’s her job to know.

Her job is Lake Baikal?

No, her job is Lake Superior. When classes are in session, she rises early and catches the number seven bus over to the state university campus in Duluth. In the morning she gives lectures; in the afternoon, she’s on the shore or in the lab. By dusk, she’s sitting in a pool of yellow lamplight at the dining table, analyzing data and writing up results that she has never tried to publish. Her husband makes dinner. Cauliflower soup. Ratatouille. Spaghetti with clams. It used to be that when he saw the crescent-shaped wrinkle where her forehead meets her nose, he strode over and bent down and dropped a kiss in her hair. He would have liked for her to tell him why she was worried, but she didn’t volunteer it, and he knew better than to ask.

Would he have understood her fears if she’d explained them?

Maybe. But then again, their work is so different. While she arranges zooplankton onto slides or collects samples from the rocky shores of Lake Superior, he gives elegant lectures to classrooms packed with English majors. For two decades, he was famous for his passion for the material. Then came April, and now he is famous for that.

Who is April?

Listen: He was grieving. Aren’t people allowed to make bad decisions when they’re grieving? For months after the funerals, he dreamed of black roads slick with ice. Hairpin turns, bends between trees. He woke shivering in his own sweat, his wife resting a warm hand on his chest in an attempt to calm his careening heart. He waited for her to ask him what he was dreaming, what he was feeling.

Why didn’t she?

Maybe she thought that she already knew.

Had she lost both her parents, too?

No, but she’s lost plenty of other things. Her childhood best friend to cancer, for instance; her coastal hometown to the rise of the Atlantic. Moreover, couldn’t she argue—although she hasn’t—that she is losing her parents a little bit every day? To Alzheimer’s. To heart disease. To old age. With every single minute that passes, they—and she, too, she knows; she isn’t exempt from the spinning of the globe—are diminishing. Cell by aging cell. Wrinkle by wrinkle. Every hour, they are less than what they were.

Does she often think about her age?

More and more. She can remember the first time she thought about it: when she hit her thirties and realized that her hangovers lingered for days. In college, she had been able to close down the bars, stumble back to the dorms, and then rise at dawn to lace up her sneakers and jog through the silent streets. She used to feel the alcohol rolling away from her skin as the morning fog rolled off the silver surface of the lake.

And now?

As she’s grown older, she’s found that nothing rolls away quickly. Not hangovers, not sprained ankles, not the occasional aches in her hips or her knees. Not the image of April’s bare legs wrapped around her husband’s waist. She’d been worried about him after the funeral, so she’d stopped by his office with a coffee and entered without knocking. She’d dropped the coffee on the hard blue carpet—it is not true that she hurled it at the two of them, though that’s the rumor that seeped into both of their departments—and part of her still feels ashamed that someone from maintenance had to be called to come clean up her mess.

Her mess?

His mess. Theirs. Because of course, after that, there was Max.

Who is—

It’s not important. Why dwell on the details of their mutual betrayal? He sought solace in someone else’s arms; a little later, so did she. This is neither interesting nor new. It’s simply what happens to a marriage when it feels as though the world is ending.

Is the world ending?

Yes and no. The seas are rising, the bees are dying. Etcetera, etcetera. We’ve all read the reports written by scientists like her. (Although we haven’t read hers.) On the other hand, the world’s been ending since the day that it began. In different moments of crisis, other generations worried that the world was ending. Whatever happens, she intends to be prepared. That’s why she taught herself to make a fire with flint and kindling. And that’s why, after she taught herself, she taught her husband. Because that’s what marriage means. When she walked into that office and discovered that her world was ending, her first instinct was to save herself. Her second instinct was to save him.

Did they talk about it?

Here’s what they did. They went out to a tiny Italian place on the north side of town, where they considered each other over bread rolls and butter flowers. He apologized first; she apologized second. She laid her hand on the tablecloth, and he reached out and squeezed it. Together, they decided to move forward. She didn’t ask him why he’d done it. He didn’t ask her what she’d been thinking. Questions of motivation, psychology, and desire were left untouched on the tablecloth beside the breadbasket.

And then what happened?

Oh, you know. Life. The number seven bus. The essays to grade, the lab reports to complete, the groceries to purchase. They fell back into their rhythm. They were gentle with each other, cautious, as if they were carrying Fabergé eggs on spoons across a rocky beach. He left notes for her in unexpected places; she brought him wave-worn pebbles from the lakeshore. One day passed. Then another.

Until?

The week before her fiftieth birthday party, she went to hear a guest speaker at a department function, a scientist from Irkutsk who’d been offered free dinner in exchange for his insights about Superior’s sister lake, Baikal. He spoke about the similarities between the two bodies of water. Calcium deficiency, mining industries, water clarity, photic zone depths. Warming temperatures, loss of species. Nothing new there. And then he said, almost as an aside, that by next year the marathon might have to be suspended.

The marathon?

Her question exactly. That night, while her husband dreamed in their oversized bed at the other end of the hallway, she called his computer to life and clicked through search results that sent her imagination reeling. The description of the distant runners as tiny black birds drifting across an ice-white sky; the image of frozen rubble bubbling cold and hard from cracks in the surface. Over and over again she read clauses that painted the angling blue shadows cast by mountains. The thick, soft quilt of gray clouds. She lingered on photographs that captured scenes as otherworldly, as unlikely, as a peacock with its wings outstretched, skimming over the foamy waves of Lake Superior. She leaned back in her husband’s chair, her mind fluttering on moth wings toward the light of his computer screen, and an idea began to emerge in the dark like the haunting mass of an approaching iceberg.

Did she tell her husband?

Not yet, no. She waited a week. She waited until the night of her fiftieth birthday party, when he crawled into bed beside her after loading the dishwasher with highball glasses and scrubbing frosting from the counter. She didn’t know what he’d been thinking earlier that evening as he’d watched her slicing limes. And so she didn’t understand why, when she wondered aloud if she might be too old to attempt it, he didn’t immediately reply: “No. You’re not too old at all.”

If he didn’t say that, what did he say?

Nothing.

Why not?

Maybe he was grasping for words in the dark. Maybe he just couldn’t reach them.

Did he know that he was being tested?

He knows that she takes her Earl Grey with cream and cinnamon. He knows that her ankle cracks with almost every step because in high school she played hockey on a broken foot and the bone never healed correctly. He knows that she can identify birds by their shadows. And so he also knows that when she said that she felt old, he was supposed to correct her.

Why didn’t he?

He was angry about the children.

What children?

Their children. The ones they didn’t have. And so he didn’t correct her. And now he is certain, as he stares through his dark kitchen at the lump of the landline on the wall, willing the phone to ring over the sound of black waves thudding against the cold shore, that this is why she went.

Is that why she went?

She’s trying not to ask herself that question. She’s trying to focus on the movement of her legs and the placement of her feet. She’s trying not to think about her husband, or her house. She’s trying not to think about how much time has passed, or about the sound of the ice growing louder beneath her shoes. She’d read that once you start the race, you shouldn’t look at who’s in front of you and who’s behind. That’s why she is pretending that she’s not the last one on the course. She’s fixed her gaze on the ice that’s five yards ahead of her so that she won’t see the volunteers waving frantic flags in her direction. She won’t see the tourists with their mittens over the black circles of their mouths. Her heart is in her ears and the wind is picking up, and so she can ignore the voices that are calling out to her.

Is she frightened?

Of this lake? This race? No. She’s prepared. As a girl, she used to speed skate around lakes. The frigid wind chapping her cheeks, her lips. Her limbs tingling, thrilling as she soared beneath black, leafless branches. Since none of the ten thousand lakes in the state freeze long enough anymore, she trained for the marathon at the indoor rink where Olympic skaters used to race. It was airy, empty, clean, cold. Haunted by the ghost of a sport that no longer exists.

What is she feeling?

The groaning of the ice. The sudden change in temperature. She was serious when she told the runners that they would be fine, but she didn’t tell them what she meant by fine. She did not describe what she already feels for this sister lake of Superior: that familiar, intoxicating combination of longing, guilt, and dread. She could not have explained to them, just as she could never explain to her husband, how her passion for the lake consumes her, how her fear for it laps like hard, cold waves against her heart, how she has always known in her bones that the love she possesses is as finite as phosphorous or coal and that she would not have been able to drill down in her soul to find the reserves she needed to love a child. She is not a poet, after all. She doesn’t have the words.

What does she have?

She has her husband, five thousand five hundred and twenty miles away, yanking the heavy receiver from its ancient cradle to place an emergency call to Siberia because it has been seven hours and she’s still on the course.

She has her body, half a century old and hurtling across a body of water that is tens of millions of years older than that. She has her thudding heart, her pumping arms, the blood in her ears that sounds a lot like open water.

She has words bubbling up like hot springs in her chest: all the things they haven’t told each other. Suddenly, out here beneath a slate-gray sky with the sting of the wind in her eyes, she has no idea why they’ve both kept silent.

And so?

And so if she is picking up her pace, if she is breaking into a headlong sprint, it isn’t because she senses the ice that is falling away behind her. It isn’t because of the wake she is leaving, the cobalt water shimmering like a contrail, the lake opening wider with every thundering step.

Is she trying to outrace her fate?

She’s trying to catch up to it.

Is it too late?

That depends. How fast can she run?