When the Mover passed, the rest of the world ceased to exist.  There wasn’t room for anything else.
The titanic engine emerged first as a sound, far out of sight, and little more than a subsonic thrum of anxiety.  It would grow in volume, and become visible as a dark blot among distant trees and hills.  And it would grow, and grow.  Once it was within a mile, the sound was deafening.  It was the roar of the earth itself rejecting the magnetic beast, of metal grinding on metal, of machines within machines within machines.  The cacophony was the world, for all time. It would only begin to fade with the imperceptibility of the end of eternity.  Feeling would return first, to limbs shaken by the vibration of the earth.  Hearing would be reluctant.
Geir had only rarely left his noise-suppressing hood down when the train passed.  He had plenty reminders of the thing’s magnitude, without experiencing all one hundred and twenty decibels of its roar.  The way it warped its rail just by traversing it was enough.  Let alone the wake it left, creating waves of frost melted by the friction and rolled aside to freeze again in brittle hoars, rippling diagonally out from the rail.  Or the birds that dropped out of the sky, disoriented by the sound and pressure, their air sacs ruptured.
When the Mover was well past, Geir returned from the shelter of the tree line to resume his route.  In his padded coat and coverall, the train left a sweltering heat behind, as much from its magnetic propulsion as from the exhaust it vented.  The Arctic cold would swallow it back up, soon.
His wristband computer showed him two anomalies within a kilometer of his position.  The first he could see from here.  The lower wall of the rail was twisted by the heat, the metal puckered outward like a six-meter line of scar tissue.  Geir double-tapped on the anomaly with one talon to flag it, and took a picture.  One of the six-legged repair robots would make its way there to tease, weld, and grind it flush.
The rail itself was almost three times as tall as Geir, a slab of steel taller than a house and fifteen hundred kilometers long, with a track inset two thirds up its sides for the Mover’s wheels to hold from underneath.  It hummed softly, even when the train was far away and stopped.  What went on inside it was above Geir’s paygrade to know, but he knew it at least housed the fleet of repair bots.
Geir out his left side to the rail and walked.  His route was one hundred kilometers east to west, just about halfway along the rail’s length.  He had about another day’s worth of walking before he reached its eastern extremity.  And it would be just over fourteen hours before the train came back the other way.
He dug the carcass of a bird out of the re-freezing slush. It had hit the rail at full force, disoriented.  He threw it off to the side, where the train’s wake wouldn’t catch it when it came back west.  When Geir missed the bodies of small animals near the rail, they accumulated, carried along, rolled against the ice and strung with one another into a string of gelatinous gore that would eventually settle and become a diagonal stain in line with the waves of ice.
It was no danger to the train, but Geir preferred not to let it happen.  Human colleagues, when he returned to the terminal, snickered at what they called a preoccupation with carrion.  He had stopped engaging with them.  
When the sun went down, Geir called his base station.  He liked it to keep its distance during the day, following him at a distance of four kilometers instead of walking alongside him as the company recommended.  He’d had many years to fine-tune the way he did his job, after all.  The lumbering robot caught up with him as he was staking out a campsite, a safe thirty meters out from the rail.  It studied him with the two small cameras slung underneath its coffin-shaped body, which were all it had for a head, until he gestured for it to set up camp.
The base camp carried a single folding chair and a portable fire pit, and contained his pantry.  Geir selected a packaged meal of beans and meat, reheated it, and watched the stars emerging as he ate.
“Want some?” he offered a forkful to the base station.
The robot stared, waiting for a recognizable command.
When he was finished, Geir deposited the meal’s tray in the base camp’s compactor, and patted on it to open its lid.  The robot leaned forward and opened up, to accept the zoan into its padded interior.
Geir had slept out in the cold for the first few months on the job.  He’d moved past romantic notions about it since then.
At dawn, Geir packed his campsite back up and told the base camp to resume its four-kilometer distance.  He set his coat aside and pulled on his protective gloves, and worked the trunk of a blasted juniper with his fists.  He had learned quickly that his arms became soft and sore when he walked the rail for weeks on end without working them.  He wore the gloves down faster than any of his colleagues.
Another mark came up on his display, a few kilometers’ walk farther.  It was a repair bot, fallen from the rail and inert on the ground.  Geir checked it over, and tried to sync it with his wristband.  It had completely failed, and its battery was too low even to return a signal.  Geir folded its legs down as best he could and hefted it to carry with him.
The robot’s body was a flat rectangle, that could rest against the rail when not in use.  About fifty by eighty centimeters, and five or six deep.  On the occasion that he had to handle one, these always reminded Geir of the atlas in the library in the receiving home that had taken him in after he had been decanted.  Memories of taking it from its stand and carrying it over to his beanbag chair to pore over, tracing the lines in it that he didn’t know the meanings of for years.  The black and brown ones printed centuries ago; the blue ones drawn in more recently by hand, to show where the coastlines were now.
Geir used to resist memories of the time before he volunteered.  He didn’t anymore: he recognized the firm barrier between then and now.  It didn’t bother him anymore to be reminded.  But it also didn’t bear thinking about.
His wristband showed him the nearest drone slot in the rail.  He tapped a switch in his wristband to open it, and deposited the dead bot inside.  Something took it and drew it in, and the slot snapped shut after it.  Geir cleared a dead squirrel out of the way, and kept walking.
At fourteen hours from the Mover’s eastward passage, Geir left the rail to wait at the tree line, resting against one of the nearest birches, whose railward branches had all been stripped bare.  He put his hood down and let the cool wind rustle his feathers.
The train didn’t come.

The operation was routine.  The target traveled and had an easily found schedule, and he drank alone between meetings.  Robin presented herself to him as an equally lonely visitor at the hotel bar, while Sparrow and Dove monitored from the room adjacent to his.  The human engineer confessed a “fondness for bird women,” and invited her to his room.  Once he was drugged and unconscious, Robin let Sparrow and Dove in, and they set to work.
The body wouldn’t need to be hidden or disposed of, though the team was prepared for that contingency.  With his history of conspicuous melancholy and alcoholism, no one would be surprised to find the engineer dead alone in a hotel room.  And Robin had been careful to avoid cameras and witnesses.  She might be memorable, a well-dressed zoan in an upscale hotel, but she also knew how not to draw eyes.
Sparrow prepared the poison, while Dove looked through the target’s briefcase and luggage, scanning any documents he found with a wave of the camera in his thumb.  Robin suited up and prepared to vacuum any feather dust she had left in the carpet or on the human.
The alert came in through all of their subdermal earpieces at once.
Expedite operation and return to base.
The accipiters exchanged a brief glance, and packed their equipment back up.  Before they withdrew, Sparrow covered the human with a pillow and fired two silenced rounds into his head, and a third into his chest.
“Could have been done anywhere,” Robin complained while they loaded back into the aircar secreted on the roof.  “Could have been done by a drone.”
“But it got done,” Dove said.
“But what’s so important,” Sparrow said. “That there’s no time to do it right?”