H felt the train judder sharply as she was freshening up. Experience had made her used to loosening her body and widening her stance to ride out bumps and jolts without losing her footing, but as she'd been leaning over the sink she was off-balance and had to brace herself against the wall. Out here in the void between stars this was unusual, but not unheard of. There was almost no interstellar dust or debris in this expanse save that which was left behind by the trains that periodically traversed it.

After the disturbance passed, H finished tying back her hair and stepped back, straightening out her uniform's simple grey skirt, blouse, and jacket while trying gamely to smile into the mirror. When she was at her best, she smiled easily; it lit up her face with prominent dimples and twinkling eyes. It was something people had complimented her on since she was a young girl, and she was proud of it. Tonight, though, it wasn't working: she could make her mouth smile, but she couldn't hide the fatigue in her eyes. Too many night shifts in a row had taken their toll. Luckily, tonight would be the last for a while. Tomorrow she could rest, and after that she was scheduled to switch to another set of cars with a different diurnal cycle, where she'd be working days. Day shifts were busier: plenty of hungry and thirsty passengers to sell to, trash to collect, and spills to clean up. It was tiring, but she preferred it to the monotony of nights. Long hours of pushing a full cart through near-empty cars, with no one to talk to and little to do, left her drained and dejected.

She stepped out and took hold of the trolley cart. She'd already loaded it up with drinks and snacks; she doubted more than a few would be sold all night. Many of the passengers in this section had gotten off at the last station, and most of those that remained would be asleep. H slid open the door to the first passenger car in her section, stood up straight, and pushed the cart down the aisle.

Many cars later, still just partway through her first run, her feet were killing her and it was becoming hard to keep her eyes open. All she'd sold so far were a few drinks: one to a willowy, intellectual looking woman who was engrossed in some kind of manuscript and barely made eye contact, and the rest to a group of raucous students who were staying up all night playing cards. Most of the cars had been empty, or nearly so. This was how it usually was on this line. Where it started, at a major station in the core, every seat was filled; then as they traveled down this minor galactic spiral arm more and more passengers disembarked at each station, with few boarding to replace them.

This next car was completely empty. She took a moment to rest her legs, sitting down in one of the empty seats and peering out the window. Outside was a vast dark expanse, dotted only sparsely with stars. The center of the galaxy was visible only as a faint band running from end of the sky to another, like lights on a distant shore. The only other notable feature was a distant nebula: an eerie red ring that resembled a gigantic bloodshot eye staring into the void. H was a core girl through and through; this bleak starscape made her long for the night sky of her home planet: a coruscating nimbus of gold, white, and blue so dense that individual stars were difficult to discern with the naked eye. Before she'd visited the outer regions for the first time, she had never experienced a night so dark that one needed to carry a lamp to see. Some people said they found life in the remote spiral arms peaceful, but H thought she would go mad if she were confronted every night by such a barren void. It made her feel small, alone, and exposed.

As she stood up and turned back toward her cart, H thought she saw movement out of the corner of her eye, somewhere in the aisle ahead. Had someone come into the car from the opposite end? She turned to look straight ahead and didn't see anything in the aisle or the seats ahead. She must have imagined it. She gave up and started wheeling the cart towards the next car, but stopped again after just a few steps. There it was again. Something was definitely moving amongst the seats off to the right. She turned in that direction and again saw nothing. All of the seats were empty; no one was in this car but her. And yet she clearly seen movement. What's more, she had an uncanny feeling of being watched. She remembered the nebula out the window, that great unblinking red eye, and shuddered. The late hour and the foreboding starscape outside were clearly getting to her, making her imagine things. She shook her head and briskly pushed her cart toward the door.

H firmly slid the door shut behind her as she exited the car, took a breath, and turned toward the hopper built into the wall. Checking these was hardly her favorite thing to do, but this time she was glad for something to occupy her mind. These hoppers were the outlets of the debris-clearing system. Interstellar dust, micrometeoroids, and trash left by other trains posed a hazard so there was a system that redirected such objects to a safe relative velocity and drew them inside to be collected in these hoppers; one in the gangway between each pair of cars. She didn't understand at all how the system worked, only that it was made possible by properties of the altered physics in the volumes of space that trains ran through: the proverbial "tracks". She opened the lid to the hopper and looked inside. Nothing but a layer of fine dust; not unexpected this far away from any stars. She emptied the hopper into her trash bag and moved on.

The next car was again empty, but someone in an aisle seat had left some trash behind. Candy drops were spilled on the floor beneath the seat and a white drinking cup was sitting on the armrest. H knelt down to gather up the candy; it was a popular snack from a gaseous planet in this region, made from a small aerial creature that floated and bobbed in its endless skies. Their skins were cured with sugar, and their body cavities — hollow for buoyancy — were stuffed with some kind of filling. They'd loaded on whole crates of this candy at the last station, and H and the other concession workers had sold plenty of it over the past few days. There were several boxes of it untouched on her cart right now in fact, and she had a momentary urge to help herself to one. Better to keep moving, though.

After gathering up all the candy drops in her hands, H stood up and dumped them into the trash, then picked up the cup from the armrest. As she brought the cup over to the trash bag, she happened to glance inside — and gasped. There was still some water at the bottom of the cup and within it, dark shapes were floating. Not floating, but moving. The water was sloshing in her unsteady hand, but the shapes moved against the currents uncannily, as if animated by some will and purpose. Not just flotsam, but something alive. Startled, she let go of the cup and it tumbled into the trash bag. She stepped back and eyed the bag nervously, almost expecting whatever it was to come bursting out. After a few moments she shook her head. It must have been nothing. Fatigue was making her edgy; tomorrow's rest couldn't come soon enough.

It was two cars later that she knew she wasn't hallucinating. As soon as she opened the door, she heard it: a buzzing, like nothing she'd heard before. Like the sound of a flying insect, but discordant; wrong. It was at once both a piercing whine and a rumbling growl and it wavered, sometimes loud and sometimes soft, making it very hard to judge where it was coming from. Perhaps everywhere. H gingerly took one step forward, then another, looking in all directions. The car was completely empty. No one in the seats, no one in the aisle, and nothing on the floor. Having no way to go but forward, she continued, her hands quivering on the cart's handle.

Around the center of car, she jumped. All of a sudden the sound was much louder, and directly behind her. Her heart pounding, she whipped her head around and was confronted with an ungainly flying thing hovering directly in front of her face. It was long and thin, like a pen hanging in midair, and colored dull grey with a sinister pattern of black spots running down the sides. She shrieked and jumped back, knocking into the cart and sending it skidding down the aisle as she struggled to keep her balance. She batted at the flying thing and it was too slow to dart away; clipped by her hand, it broke into fragments that tumbled to the floor. The brief instant her skin had been in contact with its surface, she felt it warm and vibrating; poised and quivering with some unknown purpose. Her hand tingled.

She squatted over the area where the pieces of the flying invader had fallen, and carefully gathered up each of the metallic shards that were scattered in the aisle and under the seats, using a cloth to avoid touching them. Then she dropped the pieces into the trashbag on her cart. This she had not imagined nor hallucinated. A pest had been loose in this part of the train. She still didn't know whether it was an insect that would sting and bite, or an autonomous scavenging machine that would wreak havoc with circuits and equipment, and she was certainly not going to dig out its remains and find out. What she did know was that where was one pest, there would be more. She hoped she wouldn't see any more of these flying, buzzing vermin, but she knew she probably would. She trembled as she resumed pushing the cart down the aisle, glancing furtively behind her and to either side.

As she cautiously slid open the door to the next car, H was afraid she'd find another flying pest. But what she did see and hear made her jump back and slam the door shut. In the center of the car, the aisle was filled with a swarm of flying… creatures, robots, whatever they were. There were several larger flyers like the one she'd seen earlier, and surrounding them was a cloud of smaller objects that were too small, numerous, and fast-moving to make out. The buzzing was deafening.

With an airtight door safely between her and the buzzing swarm, H pulled the intercom off the wall to call the nearest conductor room, many cars back near where she'd started. Static. She tried the next-nearest, very far ahead past the car where the swarm was lurking. Static again. Maybe those vermin were indeed cybernetic scavengers and had stripped the cables. Or… could something be going wrong further up and down the train also? She swallowed. No. This was just a pest infestation in the aisle up ahead, and she'd have to step out, disperse it, and continue with her route.

She stared at the closed door for what felt like a very long time, her heart pounding and her ears throbbing as blood rushed through them, before working up the courage to look again. She opened the door just enough to peek through with one eye, ready to leap back and slam it shut if any of the entities came in her direction.

The cloud of flying objects was still swarming in the aisle, not moving around the car but circling around the same area, all diving and whirling about as if performing some inscrutable mating dance. As she watched, there were occasionally flashes of light like sparks among the swarm. Abruptly, one of the larger shapes broke in two, its halves tumbling to the floor. They were… fighting? Each other? H stared, breathless. There was a flash and another of the long grey flyers shattered. Then another. Now there were two left. One turned and headed directly for the door where H was standing. She winced, but before she had the chance to react, the other remaining flyer dived and then slammed into the first from directly below. Their entangled carcasses fell to the floor.

Now there was nothing left but a scattering of smaller shapes, no larger than the head of a pin, hovering and circling seemingly aimlessly. The noise had died down. H pulled a cloth from her cart and then cautiously opened the door and walked forward. When she reached the area where the tiny mites were circling about, she wrapped the cloth around her hand and swung it back and forth through the midst of them. After a few swings she couldn't see anything else in the air, and the cloth was dotted with the pests' remains. Then, she looked down at the floor where the remains of several of the long grey ones lay. Grimacing, she lifted her foot and stomped on the larger fragments, breaking them down until there was nothing left but a scattering of metallic shards. With the edge of her shoe she pushed them all together into one pile, which she then bent down and gathered up into the cloth. Holding the cloth gingerly in her outstretched arm, she walked back out of the car and dropped it into the trashbag attached to her cart. That was the end of that. It had to be the end. Let the rest of the night go quietly.

H felt her whole body trembling as she pulled the cart back through the aisle to the next car. She was jittery and yet also very, very tired. Her movements were sluggish and imprecise, as if her body were lagging two steps behind her mind, struggling to catch up; and her attention jumped from place to place, unable to focus anywhere. All she could think was that she wanted to be somewhere else. The passenger car around her felt small, confined; and the starscape outside the windows was bleak and foreboding. It had never bothered her before that the stars outside the window remained still no matter how fast the train was actually moving; she knew it was because the stars were so immensely distant. But now the illusion of motionlessness made her feel trapped, entombed. Oh, to be somewhere else. No endless line of empty passenger cars. No buzzing, darting grey vermin. No nebula's red eye staring from across a barren void.

She thought of late nights by the lake near her home, laughing with her closest friends, taking swigs directly from a bottle of silverberry wine, looking out over the lake blazing with the reflected light of millions of stars. She immersed herself in that image as she vacantly trudged onward.

What she saw as she opened the door to the gangway passage shattered her reverie and brought a great wave of fear crashing back in to buffet her tired mind. A large hole gaped in the side of the debris hopper; its walls were twisted outward as if it had been punctured from within. Resting on the floor against the opposite wall was a meteoroid: an irregular brownish spheroid about the size of a beachball. The rock was weathered with scars and pockmarks, but there were also incongruities which no natural process could have brought about: metallic patches and spots marred the surface like mold or a rash. This rock was infected; a contagion, something unnatural and wrong, had spread across part of its surface.

At first H froze, unable to do anything but stare at the befouled meteoroid. No. Not more. She was so very tired, and badly wanted to close the door and flee the way she had come, forgetting what she had seen. But even as she stood transfixed, her fear gradually gave way to loathing and anger. The corruption on that rock had been the source of all of terrors she had faced tonight. Of that there could be no doubt. Even now, she thought she could make out specks circling in the air around the meteoroid in uncanny whirling patterns, like motes of dust animated by some malevolent alien will. If she left without cleansing the rock, its corruption would continue to fester; to spread further across the meteoroid and send more minions to eat away at circuits and equipment. And because of all the torment the spawn of this corruption had caused her, she wanted to end it. Now.

H cried out and ran through the door, lunging at the rock with her right leg outstretched, aiming at the largest patch of infected surface. She barely missed and her heel dug into the rock. She had to tug several times to extricate it, bracing her arm against the wall and her other foot against the rock. As she struggled she faintly felt stinging or pinpricks along her ankle and lower calf. After extracting her heel, it had left a small dark hole in the surface, surrounded by hairline cracks.

She kicked again and again; the fissure her heel had made widened until finally the rock was cloven in two, revealing a sight that made her immediately regret the terrible folly of having disturbed the thing. The stony exterior had just been a brittle shell concealing a corruption far more malignant than she could ever have imagined. The meteoroid's interior had been wholly gnawed away, digested, and reconstituted into a hive that was sickening to behold: a byzantine honeycomb of paper-thin layers and cavities which twisted and folded upon themselves into fiendish spirals and knots. Hair-thin capillaries throbbed with a sickly, pallid glow, and dark, viscous fluids oozed out of pustules near the center. Sinister grey shapes like the abominations that had been flying about earlier lurked in a larger cavity near the outer edge. But what was most unnerving was that the horrid nest was teeming with movement, everywhere, as if boiling. Foul, tiny shapes stirred beneath the surface, individually almost too minuscule to be perceived but collectively forming a writhing, seething swarm.

H shrieked and turned away, leaping back through the door and slamming it shut. Almost in the same motion, her hands moving as if by themselves, she did what she now realized she should have done from the beginning. She turned the crank that would fully re-seal the door, making it airtight. Then she uncovered and pulled the manual release that vented the contents of the gangway behind her into space. Finally she collapsed against the door, panting, sweat trickling down her back and her clammy hair clinging to her forehead. She felt the car shudder with the force of decompression and let her knees go slack, gradually sinking to sit slumped against the door.

As she sat, she closed her eyes and tried to forget everything she had just seen and done. But an image came unbidden and would not be driven away: the split halves of that loathsome nest tumbling through the void, their grotesque contents spilling out leaving a spiraling wake of tiny frozen carcasses like dust. She gagged. She'd seen inside the nest for only a moment before fleeing and flushing it into space, but even that fleeting glimpse had left its labyrinthine tunnels in all their minute, mad intricacy indelibly burned into her mind. For years to come, it would haunt her on sleepless nights, and she was never able to smile as she once did.

Though its name is now whispered in certain circles as a legendary ship of the damned, like the Flying Dutchman of old, the colony ship S.S. Agistri began its voyage uneventfully enough. It was one of many similar generation ships launched during that first exuberant wave of attempted extrasolar colonization, constructed by hollowing out an asteroid a few kilometers in diameter — a volume suitable to support a population in the thousands — and attaching mammoth ion thrusters to propel it in the direction of a nearby star system believed to contain Earth-like exoplanets. Each year it dropped a relay buoy, forming a network like a trail of breadcrumbs along its course, which allowed it to send dispatches back to the solar system without the signal fading to nothing over the immense distance.

At first these dispatches were routine and unremarkable; everything was going smoothly. However as the distance increased and the transmission delay lengthened from days to weeks, weeks to months, and months to years, the dispatches from the sons and grandsons of the original crew evinced steadily deteriorating conditions. A series of accidents diminished the ship's stocks of essential supplies, including water, and there were increasingly frequent references to equipment malfunctions. The later dispatches also contained oblique, enigmatic references to cultural practices which no one back in the solar system could understand in context. It was clear that the descendants of the original crew were not as competent at tending to the immense ship, and that in isolation their culture had diverged from that of the solar system.

Yet not even the most pessimistic observers predicted anything like the cataclysmic descent into madness chronicled by the S.S. Agistri's final dispatch, which reached the solar system a few years after what had almost certainly been the final days of the generation ship's population.

The fragmentary and badly attenuated state of the message made it impossible to fully interpret, but it was evident that the S.S. Agistri had suffered some critical accident. No information could be gleaned about the nature of this accident, only that it was of a severity that dwarfed the incidents of previous years and called their short-term survival into question. But it seemed that apart from this accident's direct impact, it had also caused something of a civil war to erupt within the ship's passages, as splinter groups saw an opportunity to rise up and seize control. Cults that rejected as lies the idea that their world was a ship traveling to a distant star. One group proclaimed that they weren't in space at all, and that a promised land lay outside the ship's hull for those brave and worthy enough to step outside. Another insisted that their world was all that existed, and that to ever attempt to leave would be to invite madness and divine punishment. The message spoke of a control center besieged by rioters, and of almost all of the shuttles and landing transports being stolen by fanatics and launched for unclear reasons.

The final message ended there, and the solar system was left with nothing but conjecture about the ultimate fate of the S.S. Agistri and her crew. The most plausible theory is that the mysterious accident, combined with the open violence among the crew that followed, led to a catastrophic loss of life support and that all aboard quickly perished. There are also countless rumors and outlandish theories, invoking everything from marauding aliens to rebellious computers, and from wormholes to dark matter. The popularity of such speculation is driven in large part by one discrepancy which has thus far defied explanation by all conventional analysis: the S.S. Agistri's final message is badly redshifted, suggesting that the vessel was accelerating away from its last relay buoy much faster than it would have been able to propel itself under its own power.