Help is a billion years away when the wave closes in on Okana. I aim all my cameras at the spot she disappears. She should have deployed her airbags by now, should have surfaced in a white protective ball of reinforced polymer, but there is only an avalanche of whitewash. The wave towers above me, a mountain about to fall. Travel back, that’s the plan if all else fails. I wait as long as I can, until the mountain is collapsing on me, then I signal Ken.

An intense cold, like I’ve been dunked in the Arctic and snatched out again so quickly that I don’t get wet, then I am bobbing on my surfboard in the pool at the university. I strip out of the spacesuit.

“Is she here?”

Ken, the freckled post-doc who runs the time machine, points into the water below me. The locator nodes that Okana wore on her spacesuit, identical to the nodes Ken used to pull me back across the epochs, lie in the bottom of the pool. The wave ripped hers off.

“Send me back. I have to find my wife.”

Ken shakes his head. “Takes a while to recalibrate the machine.”

“She’s out there all alone. I have to go now.”

“What’s the hurry? It’s a time machine.”

I pack up everything into our little electric car, strap the board to the roof rack, and then I am back at our home in Hana. I don’t remember the hour and a half drive. I go inside and load the footage into my studio’s servers. As I’m going through what I captured a billion years ago, I bring up more recent history on another monitor.

The video is almost twenty years old, filmed on a GoPro I stole from a tourist in Kihei. Okana is all gangly eleven-year-old limbs and sun-browned skin floating on her too-long longboard.

“One day, I’m going to surf the biggest wave in the world,” she says.

Droplets of water blur the lens so I can’t see her expression.

“We should probably go in,” I say from out of frame. We’d been surfing for hours.

“Not yet. I’m not ready to go back.” Back to the shack where she and her eight brothers sleep beneath the leaking roof, she means. She starts to paddle. “Here comes another set. Get a decent shot this time.”

I stop the video. I’ve followed that command ever since.

There are so many of these clips, thousands of hours of her life, but that’s the first clip I can find where she mentions the big waves. The really big waves.

On the main monitor, the biggest wave ever surfed is frozen mid-curl, nine hundred feet high, Okana a tiny white speck halfway up its face. Messages from our producers and sponsors fill my inbox, asking when I’ll be ready to send them the footage of Okana on the uberwave, but I ignore them all. I go through everything I collected, frame by frame. There has to be something. Why did she strip off her locator nodes?

I queue up another clip on the side monitor.

I pilot the jet ski that tows Okana into Peahi. At fifteen, she’s the youngest woman to attempt to surf Jaws. Surf reports put the wave at forty feet, maybe forty-five. Her expression is pure concentration: little furrow of her brow, mouth clenched tight. I capture the footage on GoPros—one strapped to the nose of her board and the other to her wrist. A drone flying twenty feet above her streams footage to the console on my jet ski. I keep the focus on her athleticism, her arms as she paddles into a wave, wide-angle shots to show her mastery of the board, dried salt on the muscles of her shoulders.

She releases the tow line and drops in. I remember my heart hammering as she wavered on her board.

I scroll through the footage of her coming out of the barrel, and I stop when I see her face as I swing back around to pick her up. Ecstasy and awe and pride all wrapped up in one huge smile as she crawls up onto my machine.

I deleted the footage the drone captured of what happened next. At the time, I wanted our first kiss to live only in memory. Now I wish I could see it again.

It’s after 9 pm when I call Ken. He says the machine will be ready for another drop tomorrow morning. She is back there, one billion years ago, lost in the primordial ocean. The Earth back then is a rocky orb without atmosphere, without life. A thin skein of ocean sloshing across its still-cooling skin. Meteors strike at whim.

When she came up with the idea last year, it had been so romantic. “We’ll be the only two people on the planet.”

“It’s too dangerous,” I said. “No one has surfed anything close to that size, and we’ll have to do it in space suits.”

We were lying in our separate beds beneath our water-tight roof, both of us propped up on our elbows as we stared at each other.

“We can do it. You know we can.”

“A meteor strike causes the wave. Surfing it is insane.”

She stepped out of her bed and slid under the sheet in mine. “When have we let insanity stop us?”

I run the uberwave footage in reverse. From the mountain of foaming spume, Okana emerges on her board, going backward. She rides up the colossal face of the wave. She tames it the higher she climbs; she coaxes it back into the primordial ocean. The fire burning the atmosphere rolls back from the horizon, over Okana’s head. She pushes the wave back to the point of impact. The ocean heeds her command. Waves from all directions converge on the point where the meteor struck. She is a goddess healing the Earth; for now, the ocean spits out the flaming meteor, throws it back into the sky, out into the dark void. The infant Earth is whole again.

At the end, it is just the two of us sitting on the wine-dark protosea, the sky full of alien constellations.

I pause the video there and go looking through the old files. Hard drives full of her. It takes an hour for me to find what I am looking for.

Three years ago, Okana silhouetted against a half-set sun. “Out here is the only place I really feel alive. Everything else is interstitial. Like I’m waiting for the next wave.”

I learned not to interrupt during these moments long ago. Surfers think they are philosophers, a conviction that comes from years of having one’s head held underwater, but my wife is a true thinker. Yet I am silent out of more than just professional courtesy. Our life is those moments between surfing sessions. The conversations about having a child, the home we’ve built together, the plans for the next big wave. I am the interstitial.

The first time we used the time machine, we went back to Lituya Bay in Alaska, 1958. I cue up the footage and tell myself I will go to bed after I watch it.

The rock slide occurred in the middle of the night, so my drones were equipped with infrared cameras. Had we tried to use lights, Ken had told me, we would never have been allowed to travel back here. Not by him, but by history itself. The machine wouldn’t have been able to send us there. The witnesses who survived the Lituya Bay tsunami did not describe lights on the face of the wave, so we can’t use visible lights.

When humans perform some delicate scientific experiments, Ken said, the act of observation affects the outcome of the experiment. It’s called the Observer Effect. But history protects itself from even that. When we travel through time, we have no impact on events. Our boards cut through the water, but the ripples we make are devoured by the vast wave of history.

I’m on a board that is a prototype of what we will use for the meteor strike: retractable turbines so we can get up on the wave, avalanche airbags strapped to our wetsuits in case we get swallowed.

“We don’t have to do this,” I tell Okana in footage that we never aired.

“This is what we were born to do.”

A deafening crash echoes across the bay as half the mountain collapses.

I speed up the video by a factor of ten. The wave rushes across the bay, picks us up, tosses us around like toys. I follow when she starts to surf, stay close to get the best angle. We surf right over the La Chaussee Spit and are launched out into the Gulf. Here I slow it down.

Okana is on my board. We’re peeling the wetsuits off each other. The Gulf is frigid but we are warm as we make love in the churning darkness.

After, we lie shivering on my board, Okana on top of me.

“We should get Ken to bring us home,” I said.

“There must be something bigger than this.”

“This was the biggest wave in history.”

“Before history. Before man. The meteor that killed the dinosaurs landed in the ocean, right? Or even bigger ones before that.”

The wave she dreamed of hangs mid-collapse on the main monitor. The whitewash where Okana disappeared fills the screen, but it’s not the whitewash I am looking at. I don’t know how I didn’t see it before. In the dark, tumbling water, there is the hint of a shape below the surface. A person on a surfboard, pointed toward the wave.

The wave didn’t strip off the nodes: Okana pulled them off.

The sun is rising above the Pacific. I’ve forgotten to sleep. I call Ken as I get on the road.

“I need to stop her from going.” Maybe I can go back to that day when she first said she wanted to surf big waves and talk her out of it. Or further back, to the flash flood that swept her parent’s car away. “I think she wanted this. I think she wanted to be alone. I have to stop her”

“We went over this. The machine only lets us observe history, not participate.”

“But it let her stay back there.”

“It’s strange, I admit,” Ken says. “My theory is that she is inconsequential back then. There is no history to disrupt. That’s why she was allowed to stay.”

His words run through my head as I drive to the university.

Ken sends me back. Ice-cold immersion, and then I am sitting on my board in the primordial sea. The sky glows red, the sea sloshes, peaks twenty feet high roll past, but they don’t break. No one could surf these. I send out my drones, and in minutes they’ve found her.

She is hunched over her board. Her labored breathing rasps over the radio. She barely moves as I arrive beside her. “Had to come to record the ending, didn’t you?”

“I didn’t bring cameras,” I say as I screw one of the spare oxygen canisters into her suit. Her breathing improves. I hand her the mesh bag with the locator nodes. “Put them on, please. We can still go back.”

She doesn’t take the bag. Light from the still-burning atmosphere shines through her visor onto the face I’ve watched for so long. “The next one will be bigger.”

Another wave lifts us. From that height, I spot a dark wall of water that hides the horizon.

“There will always be another wave,” I say. “When will it be enough?”

She starts her thrusters and steers toward the wave. “I’ll let you know.”

I push my thrusters to catch up, my mind churning as quickly as the propellers. She might live for the waves, but I’ve been living behind the camera. Watching, only watching. She’s always been my subject first, my partner second. “This isn’t the biggest.”

She doesn’t look back. “This is the biggest impact after the oceans formed.”

“Before the oceans. The impact that made the moon. It turned the whole surface of the Earth into a sea of lava.” It will take years to develop the tech we need for the ride, maybe decades. Interstitial time. Time enough for both of us to learn new roles. “Think of it. Surfing molten rock. You and I.”

She sits on her board and considers me for a moment. I hand her the locator nodes. This time she takes them, then points toward the nearing horizon. “We catch this wave, then call Ken.”

I gesture toward the wave and say: “All yours.” Old habits.

“No,” she says. “You go first this time. I want to see what you’ve got.”

I turn my board toward the wave and paddle beneath the incandescent sky.