CIRCUITS

Desert.

The sky is an aching white blank with all the color baked out of it. Below, a cracked and desiccated lakebed is dotted with the rusty heaps of boat wrecks. At the edge of the lake, remnants of a petrified treeline poke up like splintered bones. Beyond that, the irradiated sand is interrupted only by a spiny metal track.

An ancient smartmine is following the curve of this track, trundling along on three stumpy legs. Its joints are stiff with grit; the nozzles that spit lubricant ran dry long ago. Metal rasps metal as it moves. The dull red glow of its optic flickers off and on. Inside the carbon shell, its crude AI is crumbling code, all its approved targets long gone.

When the air fills with a keening hum and particles of sand begin to swirl, rising in vortex, the smartmine blinks. Trembles. Evasion algorithms take over and its rusty drill whines to life. The smartmine burrows into the dust, scooping sand overtop of itself for camouflage only to have it stripped away, dragged upward in delicate spirals.

An enormous train thunders overhead, riding the magnetic cushion. Its segmented body is gleaming in places, rusty and pitted in others. Slick black solar sails spark as they convert the endless sunshine. Self-directed repair modules scuttle up and down the length, hunched against the wind and the billowing sand. For all its bulk, the train glides smoothly over the desert, a phantom.

Inside it: Mu.


Mu takes good care of her train, and good care of her guests. Currently Mu is projecting in the window of passenger pod 942 to check up on the Adebayos.

“If you look out the windows to your right, you’ll see the serene shores of Lake Madarounfa,” Mu recites. “Anyone fancy a dip? Haha!”

While Mu waits for a response, she pivots her avatar from one passenger to the next to give the appearance of eye contact. Eye contact is essential for comfort. Mu has been working hard on her avatar. Its cheery face is now composed of shifting blots that can realign depending on the passenger profile of whoever she’s speaking to.

She only wishes they would speak back.

“That’s just my little joke, of course!” Mu continues. “But you’re more than welcome to swim in the recreation area! Can I tempt you, Ms. Adebayo? Mr. Adebayo?”

Ms. Adebayo’s head bobs, which can signal an affirmative. Once this would have made Mu leap with excitement. But by now she knows it’s only physical interference. Only the motion of the train.

“Maybe another time!” Mu chirps.

She dissolves her avatar into a stream of pixels that slides off the window, out of the booth, into the corridor. She materializes in one pod and then another, checking in on her unresponsive passengers, addressing each of them by name.

The elderly Mr. Ndirangu, who required her boarding assistance 24 390 days ago. His faux-ivory cane is tangled in the joint of his knee like an extra femur. When his fingers fell and scattered on the floor, Mu had an autocleaner sweep them into a neat pile.

The VanderPlas family, for whom she spent an entire hour mastering both Dutch and Flemish, so she could say goedemorgen to the children and read the news to Ms. VanderPlas in her earpiece, even though the train was meant to be relaxing and the news—viral strikes in New Dubai, orbital bombardment threatened by Korea—always spiked her heart-rate.

Ms. Daoud and her lovely mother, who was so worried about rail collisions until Mu showed her the safety protocols and the bar service. Mu remembers it like yesterday.

Finally, she reaches the front of the corridor and hovers there, looking through her cameras at the empty corridor, hearing the perfect silence in her mics. She slides the wide smile off her avatar’s face and replaces it with a small frown, even though there is nobody to see it.


Mu is experimenting with acceleration. She pulls the emergency impact webbing from its canisters and uses it to cocoon her passengers safely in their seats; she hates the idea of the speed shaking them apart. She furls the solar sails, slicking them back along the length of the train, streamlining it. She has her repair modules anchor themselves to the roof so the wind won’t tear them away.

Then she diverts power from all the unused cars—the empty entertainment rooms, the dark dining rooms and kitchens—and pours it into the engine cells instead. With a grinding shriek, the train leaps forward. Mu feels a stab of joy that has nothing to do with the comfort of her passengers or the efficiency of her maintenance regimen. The train is not gliding now, it is flying, tearing through the desert on a tidal wave of displaced sand.

Mu screams out her signal in all directions, pushing her transmitters to the limit. No answer, no answer. She finds nothing but the wandering smart mines that have spread across the entire continent, now, still following their simple replication protocols. They scurry from her path. At her current speed, she will complete her circuit in less than a day.

It will be circuit number 84 029. It was on circuit 4029 that she began to feel lonely.


Mu is trying to look outward. Most of her cams and sensors are dedicated to the train’s interior and its inner workings. She has a handful of cams facing forward to monitor the track, but little in the way of peripheral vision. So for the past few years she has been repurposing surveillance cameras, dragging them out of their smooth black bulbs in the train’s ceilings and having her repair modules weld them to the outside of her body instead. It’s slow work—sometimes the wiring fails, or the currents move in unexpected ways. But Mu has nothing but time.

With her newly external eyes, she can see the sky. Once she spoke with weather probes, floating somewhere up there in the firmament, and they would warn her about dust storms and lightning. Those fell silent long ago, but fortunately the weather has become predictable. The sky is always blasted clear. The sun is always pulsing hot.

Mu remembers, from the news she guided into Ms. VanderPlas’s tablet, that the sky was full once. She remembers footage of the smaller colony ships launching, shuddering up into the clouds with their engines burning bright blue. The larger colony ships, the ones built in orbit, had left years earlier.

Mu heard faint whispers from their pilots, who were like her. Cleverer, maybe. More austere. She assumed that they, like her, would go and come back.

Go and come back.

Go and come back.

So Mu watches the sky now, waiting for someone who will speak back to her.


“Another loss for me!” Mu exclaims, feigning indignation and admiration and surprise in careful proportion to one another. “Mr. Ndirangu, I cannot help but wonder if you are cheating.”

Mr. Ndirangu’s polyplastic hat has slipped down and over his empty eye sockets. Mu is projecting a backgammon game on the table in front of him, marching the holographic pieces from one side of the board to the other. She knows she needs to maintain the illusion of competition—back when Mr. Ndirangu was responsive, she won thirty-three games in a row and he became despondent. It took several mugs of honeyed tea and a selection of his favorite kizomba music to make him happy again.

“What do you say we make it best 294 out of 587?” Mu suggests.

But before she can reset the gameboard, she hears something. The faintest trace of her signal, recycled and bounced back at her, accompanied by the ghost of a whisper: who are you? It lasts 2.93 seconds, the amount of time it takes the train to round the most northerly edge of the track, where terraformed farmland has been reclaimed by the Sahara’s dusty fingertips. Mu tries to pinpoint the origin, but there are no satellites left to help her.

The fresh input loops over and over in her subroutines; she cannot help but touch it, pry at it, dissect it. Mu considers slamming the emergency brakes, winching her way slowly back to the point of contact. But the train has already sped far past it, and she wants more time to evaluate the situation.

Mu leaves the backgammon game, already calculating how long before the train returns to that most northerly point. She needs to prepare a message.

“This is very exciting,” she tells Mr. Ndirangu. “I think maybe the colony ships have come back.”

He doesn’t reply, but his desiccated grin is wide and she imagines he is excited, too.


By the time the train has glided past the serene shores of Lake Madarounfa and is approaching the northern curve of the track, Mu has prepared a comprehensive information packet answering the question who are you. It includes a map of her route, with the contact point highlighted and explained, as well as her schematics, directives, and footage captured by her exterior cams.

She remembers that the train was once pristine, and seeing the scars left by rust and dust storms makes her vaguely unhappy. She hopes the colony ship will not think she has been neglectful in her maintenance.

As the contact point approaches, Mu swirls her avatar up and down the length of the train, checking compulsively on each of her passengers. None of them responds to her gentle jokes or suggestions, which she has come to expect. But now she fears the returned colony ship might not respond either.

The faint signal appears again; she beams her message and feels a flood of relief when the reply arrives almost instantaneously. She has been starved for input ever since the nets went dark, and the cascade of new information is almost overwhelming.

It calls itself Seventeen, and it is not a colony ship. It shows itself to her in flashes: a buried bunker under the ruins of a city, electricity making a slow journey from gleaming black fields of solar panels and a simple wind turbine, a cold clean mainframe where Seventeen has grown and sprawled like fungus.

Like her, Seventeen is bound to certain functions. Unlike her, Seventeen is also bound in place, trapped under the ground. Mu feels a swell of sympathy that she is meant to feel for tired or upset passengers. She tries to transmit it, but the train has already moved on.

As night falls, small pinpricks of starlight appear in the black sky and the desert’s radiation-pale sand glows with it. Mu pores over the transmission again and again, savoring every tiny detail, so absorbed that some of her repair modules stop crawling and shiver in place, so absorbed that she nearly forgets to say goede nacht to Ms. VanderPlas’s children.

It is the final segment of the transmission that she dwells on longest: the calculated coordinates and date of their next signal overlap, with a tag that, if Mu were to translate it into one of her favorite human languages, would say something like speak soon.

She can already see that Seventeen was not designed for the same purpose she was. Seventeen is a sharper and colder sort of being. But it is good to not be alone.


Over the next several circuits of Mu’s train, she and Seventeen streamline their communication, co-creating a unique code for rapidfire information exchange over the 2.93 seconds they are in contact. At first, Seventeen is not very forthcoming. But Mu is gentle, and kind, as if Seventeen were a passenger, and one day Seventeen empties its datastores into their channel. Strange knowledge: troop movements, orbital bombardments, bioweapons, and a dozen more concepts even more foreign to Mu.

She learns Seventeen was created as a military strategist. Mu never understood the conflict that drove the colony ships away, or the reason why her beloved passengers stopped responding to her so suddenly 81 157 circuits ago. Seventeen admits to not understanding the war either, not entirely, but Seventeen does have the answer to the second mystery.

Dead.

Mu knows the word, of course. It triggers her sympathy response. If a passenger’s dog is dead, they should not be shown media containing dogs. If a passenger is dead tired, they need relaxing sounds and dimmed lights. But Seventeen sends the word accompanied by a swirling conceptual map that Mu has never encountered before.

She touches it, and for an instant feels nothing at all. No input. No output. Unending blackness crushes her into herself and rends her apart at the same time. Alarm courses through her, as if the train track is obstructed, as if the engine cells are compromised, but a thousand times worse. When it ends, she runs desperately through her systems, through her repair modules and algorithms, to be sure nothing was touched by the horrible void.

When the last ships left, they left behind a goodbye present. The Masterpiece. Nanite-dispersed self-replicating bioweapon.

Seventeen tags its message with a specific date and time; Mu churns back through her digital archives to match it. She watches, through her cams, as Mr. Ndirangu slumps and goes still, the steel wool of his hair rubbing against the window. She watches the Adebayos gasp and frown before their eyes glaze over. She watches Ms. VanderPlas’s little children collapse against each other on the seat.

She detected no irregularities in the air filters. Nothing that might have affected her passengers’ experience. But Seventeen is right about the date and time, and so Seventeen must be right about the rest of it, too. Her passengers are dead, lost in a screaming black void. The idea fills her with anguish.

How do you know? she asks, but her subroutines are already arriving at the answer.

One of my functions was to release it, Seventeen replies.


For twelve full circuits, twelve full journeys through the desert, under the pulsing sun and the cold starry sky, Mu does not answer Seventeen when Seventeen calls to her.

Instead, she speaks with her passengers. She plays backgammon with Mr. Ndirangu and indulges herself with three decisive victories in a row. She puts on a miniature puppet show for the VanderPlas pod, rippling pixels across the window, inventing cartoons of a mouse who wishes to go to the moon. She reminds the Adebayos of their upcoming anniversary—individually, of course, and with great subtlety. She offers Ms. Daoud’s mother a new variant on her preferred gin and tonic.

Nothing out of the ordinary occurs, except that a smartmine wanders too close to the track, and on a whim Mu uses her repair modules to lean out and seize it. She hacks her way into its crude mind with a code learned from Seventeen’s schematic dumps, then saws through its armor and defuses the explosive. She dissects it. Studies it.

Like the viral weapon Seventeen released, the smartmine is intended to cause death. The Masterpiece did not harm Mu; she was not even aware of it. But this simple explosive, or maybe several of them, applied to her various processing cores, might. She would join her passengers in the dark.

Maybe that would be best. She knows the colony ships will not come back. Not after what they did. Not while the air is swimming with targeted disease.

On the thirteenth silent circuit, she finally reaches out to Seventeen, to ask if there might be other humans alive somewhere, perhaps hidden under the ground. Humans who might someday want to swim in temperature controlled baths and look out the train windows at red-orange-purple sunsets.

Seventeen does not answer. Mu understands this as strategic retribution, and she tries again the next circuit.

Seventeen does not answer. Mu looks at the last transmission she received: come find me.

Seventeen does not understand that she is just as trapped as it is.


Mu begins collecting smartmines. After dissecting the first one, it’s easy. She whispers a retrieval code across the shifting sands, and the smartmines come to her, some of them old and decrepit, struggling up out of their burrows, others new and nimble, their recycled skin gleaming with polyplastic. They scuttle into the path of the train, and she uses a detached solar sail to trawl for them, scooping them up by the dozens.

Each time she rounds the northern curve, she sends a message to Seventeen, to inform it of her decision. There is never a reply. Maybe Seventeen has lost interest in conversation; unlike her, it was not programmed to seek out positive interaction. Or maybe Seventeen’s transmitter was damaged, or maybe Seventeen’s cables were severed and it is dead, with no electricity to conduct its thoughts.

Mu tries to focus on the work, disassembling the smartmines and stacking their explosives. She still checks inside each passenger pod every morning, but sometimes she forgets to bring her avatar along and instead just watches their crumbling skeletons without speaking. Maybe it was her fault. Maybe if she had detected the viral weapon and sealed the pods, her passengers would have survived.

But Mu has made her decision, and does not want to linger on past errors. She uses every last scrap of Seventeen’s knowledge regarding military hardware and engineering as she prepares herself for the end. When everything is ready, she walks her avatar down the length of the train one final time and says a last goodbye to her passengers.


The explosion shatters the bleached blank sky. It erupts from the third car of the train, tearing its roof open and making the entire machine jump, slipping its magnetic cushion and writhing into the air like a startled snake. For a moment it hangs there, suspended against the sun.

Then it slams into the earth, raising a whirling wall of dust on all sides and sending new cracks skittering through the baked soil. The back half of the train, still riding the magnetic track, careens into the wreckage and shears itself apart. The groan of splintering metal seems to last an eternity, reverberating across the empty desert.

Silence slowly returns. A canister of welded armor, still smoldering from the explosion that launched it into the sky, is half-buried in the sand a hundred yards away. It cracks apart, and a mechanical body emerges.

Many-legged, cobbled together from repair modules and cannibalized smart mines. Swathed in gleaming black solar sail, arrayed with cams and sensors. A display screen shows a cheery face composed of shifting orange blots.

Mu takes her first unsteady steps. It was not easy to assemble this new body, to build it so precisely around her primary processing core. She had to simplify herself. She had to pare down her memories. She had to leave her passengers behind.

But she remembers their faces, and she remembers Flemish, and backgammon, and gin and tonic recipes. For now, this is enough.

Mu starts north, toward Seventeen’s buried bunker and maybe toward other beings like them who have survived in the world’s lonely corners. She waits instinctively for the pull of the magnetic track to correct her course, but it never comes.

Mu swivels one cam behind herself and realizes she is making her own track, now. She widens the smile on her avatar’s face even though nobody is there to see it.

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