The reverberations of distant clunks trembled through the ship. Drills juddered deep. Cailan listened to the unholy wail of metal scraping metal. The planet moved, pulsing, living where Cailan's parents did not.

He should tell Sum they were dead. Just tell him outright. But the smell of blood had hung thickly on the flight deck and Cailan could still smell it, taste it at the back of his constricted throat.

"Where are our mums?" Sum repeated.

"Shh. They're on the flight deck."

A shard of realisation glinted in the dark of Sum's eyes. He wasn't stupid; he always knew when Cailan was being cagey. But he still asked, "They're fixing the ship, right? They'll get us airborne."

"I don't think so." Cailan bent his head, inspecting Sum's twisted leg because his expression was worse than broken bones could ever be. Cailan needed to move, make splints, find painkillers, power cells. If the escape pod worked and Mum Ella's emergency notes were intact, they'd be in with a chance. "I'll be back in a minute. I'm not going far."

Staggering to his feet, Cailan pretended not to notice the moisture dripping from Sum's jaw, mingling with the blood.

#

The ship, broken in two, listed on its side in a crater, but the escape pod door was only cracked. Cailan tried to see that as a good thing. He pressed his nose to the window, squinting through a fine layer of reddish dust into the filmy orange mist outside. The ghosts of gigantic stacks rose to the north and east, an industrial mountain range hulking above a scrapyard valley. The two halves of the ship nestled between hills of rusted rubble and debris, tangled pipes and the burnt-out skeletons of ancient vessels. Who knew how old some of them were.

Who knew the last time humans set foot in this place.

Sum dozed on one of the bunks, a skinny arm slung across his eyes to block the pale emergency lights. It would be easier to turn them off, but Cailan needed to see Sum's chest rising and falling. Sum's ribs hadn't punctured his lungs, but his chest heaved, his breaths wet with the tears he swallowed.

Soon Cailan had to venture out and search for supplies, food—anything.

But first he needed to know the planet.

"Sum, do you know where we are?" Cailan knelt and checked his brother's temperature. Rising again; he settled a soggy ice-pack against Sum's cheek. "You tracked us in your book, right?" Sum cherished his star compendium Uncle Alun gave him on his eighth birthday. Every trip he mapped their progress, able to reel off not only the passing stars and minor planets, but also most of the decommissioned warships and abandoned stations.

"Kethell 73, I think. No human life." Sum withdrew his arm and winced. Cailan only had two days' worth of painkillers left; they couldn't stick around any longer than that. "What are we going to do, Cai?"

"Don't worry, I'll find the parts we need to fix the pod. I'll check Mum's toolkit—there'll be a welder." The toolkit was on the other half of the ship thirty yards across the metal wasteland. If Mum Ella was alive, Cailan would be excited to suit up and go outside, but alone, adventure became survival, and survival wasn't fun—especially not when your baby brother was losing colour fast. "There's stuff everywhere. I'll find something."

"But it'll all be useless," Sum said, brow lines deepening. "Kethell 73's an incinerator planet. People just dump stuff here to be destroyed."

"Yeah, and a lot of people can afford to dump good stuff," Cailan said. "Stuff that still works. People throw it away just because it's old."

Sum pondered this. "I guess."

"Can you feel any pain?" Cailan hoped Sum would say no.

"Um," Sum mumbled. "It's not that bad."

Cailan reluctantly drew another syringe. "Listen, I'm heading out soon. I'll have to leave you here, just for a while, OK? I'm going to give you more drugs. You'll sleep. Try not to move."

"Promise you'll be careful." Sum's voice came strained. In the flickering light his skin glistened, waxy-looking, like he was wearing a mask that was almost Sum but not quite.

"Do you need to be sick?" Cailan asked. "You should do it now before you sleep."

"I—" Sum shook his head and gulped. "No."

Touching unsteady fingertips to Sum's feverish forehead, Cailan administered more painkillers and waited, watching his brother's sighs even out, trying not to overthink the texture of his skin.

Once sure that Sum was out, Cailan suited up, snapping his visor into place. The suit checked his stats, pulse rate, temperature. It warned him that his wrist was sprained, which he knew, and reminded him he hadn't eaten in eight hours, which, with a dry swallow, he also knew. Cailan didn't care; all he wished was that Sum sank into a sleep so deep that nightmares couldn't touch him.

#

The smokestacks never slept.

A rickety, unused rail track sidewinded across the land, snaking from stack to stack, factory to workshop, and down into the tumbled depths of rusting waste. The rails were once used for collecting and carting debris, but the Machinists found that often the carts got jammed behind obstructions or were tossed in whirling, metal-shard cyclones.

But the Machinists now constructed more reliable transporters—efficient, self-sufficient.

And these new intermediaries did not need tracks.

#

Dirty gusts of furnace-heat strove down the valley, carrying with them the tang of burnt rubber and engine grease. Cailan's eyes watered even through the helmet's filter. Rust particles clung to his suit, forcing him to repeatedly wipe his visor, but it just smeared again, everything turning the colour of blood.

There were two more stacks, to the south and west. Every direction he turned looked the same. Mum Halley once spoke of Machinists, giant unmanned structures that controlled construction sites and mines. A Machinist's configuration depended on its assigned duty: some were small and humanoid, attached to control panels where they prodded screens to keep production rolling; others hulked the size of buildings, repairing the stacks and metal compactors as quickly as breakages appeared.

Mum Halley would have been interested to see them, but Cailan dared not go closer to the booming, hissing stacks, not with Sum back at the ship alone.

After fifteen minutes of stumbling over the tangled terrain, Cailan found organic matter sitting at the edge of an oxbow lake. The nearby river did not look safe, thin and rainbowed with oil, but the lake appeared unpolluted. Cailan collected a pouch of dark, claw-leafed weeds. It wasn't much, and he would need to neutralise it in case of toxins, but it might keep them alive long enough for him to repair the pod door, or at least get the ship back on network so he could call for help. He grabbed another handful of weeds and started to rise.

And something lumbered into his peripheral vision.

Flinching, Cailan toppled backwards onto his rump.

The dark shape that scuttled towards him across the wire hillock was not a Machinist.

It moved independently of any other machine or building, unlike anything he'd heard of before—an obscure mishmash of machine parts crudely cobbled together. It came on six spindly legs jointed at the knee and ankle points. They moved efficiently, maintaining balance of its thin torso, attached to which were two protruding pincers like grasping arms. At the top of its body sat a pyramid of scrap that jerked from side to side, sensors blinking like two red eyes, seeking, sharp and alert.

As Cailan tried to process this, he spotted another shape moving in the distance. The second, squat and tank-shaped, crushed debris under caterpillar tracks as it slugged towards the easternmost stack. The spidery creature approaching Cailan was slightly bigger than a human man; the one on caterpillar tracks a small scout vehicle.

All thoughts of Sum and the ship and his dead mothers faded back, still present but not as keen. Cailan stiffened, the urge to flee tangled with the urge to keep very still in the hope it wouldn't spot him. The creature stalked nearer, pausing to select an item of junk with one snapping claw before depositing it in a barrel strapped to its back.

The moment it registered Cailan, it reconfigured its route with a jolt and bore over the crest of the hillock. It sped down onto him crouched in the silt and tangled wires, a handful of weeds still dripping in his paralysed fist. The spiderish legs clicked and tapped over the rubble, kicking up tiny red clouds of rust flakes. Up close Cailan distinguished gears and tubing, dented fragments of steel plates, hinges and struts.

The creature sped up suddenly, jerking Cailan into motion at last. And the moment he moved, it leaped.

The clicking legs fell silent for a second, but Cailan didn't wait to see where it landed. He rolled to his feet, and hauled himself across the silt, scanning for somewhere to crawl into or under that the creature couldn't follow.

Arachnid legs came on through puddles with a wet thump-thump-thump, quicker than Cailan's heartbeat.

His helmet warned that with his hunger levels and dehydration, he shouldn't engage in strenuous physical activity. He wanted to scream at it, tear it off his face, but he could only grunt, arms flailing for balance, legs wobbly like the rubber tubing strung about the creature's body. And then he saw his haven: a hollow tangle of litzium piping.

Cailan fell the last couple of feet, headfirst, hands splayed to grip the edges of the hole and yank himself through. As he scudded into the tangle, one of the creature's legs grazed the back of his knee. Before Cailan registered stinging heat, the suit informed him of a breech. Cailan ignored it because he was through—he was through!—and the creature was too big to crawl in behind him.

Lungs searing, sweat burning his eyes, Cailan huddled in the metal and tried to catch his breath.

The thing clicked back and forth a while, selecting more waste parts and dropping them into its barrel. Finally it lost interest in Cailan, and through the mesh of debris, Cailan watched it rejoin its haphazard companions. The creatures made for the eastern stack, the factory billowing charcoal-coloured smoke in the distance, each of them carting their loot to the fires.

As soon as they were far enough away, Cailan struggled out of the tangle and, with a limp, headed for the ship as fast as his gelatinous legs would allow.

#

Even in the warm glow of the emergency lights, Sum looked worse.

"I have food," Cailan said, wincing as he dropped down beside his brother. His right knee throbbed lazy fireworks; he hadn't checked how bad it was, but it didn't seem to be getting worse, and that was all that mattered. "Come on, wake up, Sum. Look, I've got some delicious weed things. Yum."

Sum murmured, and took a full twenty seconds to come around. "Weed things?"

"Yeah, your favourite."

"They are not," Sum croaked, but he opened his mouth when Cailan pushed a few stringy bits of brownish-green against his lips. On arriving back at the ship, Cailan had run them through decontamination, and then tested for poison anyway. The weeds weren't polluted by the incinerators, but they lacked many of the nutrients Sum needed—they both needed.

Another thing they needed was a fixed escape pod, which meant leaving Sum alone again. Cailan decided not to tell him about the mechanical creatures.

"Hey, guess what I found?" he said.

Sum, too busy chewing dryly to answer, flicked hazy black eyes at Cailan.

Cailan lifted the star compendium up for Sum to see. "Now you have something to do."

"Where was it?" Sum asked around his mouthful.

Cailan set the book down on the bunk. "Under the MediPod with you all along, can you believe it? Must've slid there when we crashed." The lie tasted coppery. As Cailan redressed Sum's cuts and reset his legs, he thought about having to wash the book's cover of their mothers' blood while Sum had slept.

Cailan hoped it was the last time he had to go to the flight deck.

He flopped down on one of the other bunks, not bothering to clear it. "Got to get some shut-eye for a while," he said, but he turned his head and stared across the cabin.

Sum stroked the cover of his compendium, and for a flicker of a moment, Cailan wished he'd left the stupid book where it was. But it was only a fleeting wish—perhaps it was OK that the book brought Sum more comfort than Cailan could; it'd distract him from his injuries and give Cailan time to work on the pod.

Cailan set the alarm on his databand to go off in twenty minutes. He caught maybe six minutes of actual sleep. Around minute seventeen, he got up again and double-checked Sum, who was slowly leafing through his book.

"Why don't you find the nearest station or inhabited planet," Cailan said around a jaw-cracking yawn."I'm going to the pod. Then we can finally get out of here."

"Finally," Sum echoed. Cailan was halfway to the door when Sum added, "OK, I'll do it. But only if you let me navigate."

Cailan paused but didn't turn. "Yeah. Obviously," he said. They both knew Sum could never be the navigator Mum Ella was, and they both knew it'd be lucky if they made it as far as an inhabited planet on their own. Before he left, he turned down the lights to their dimmest, and ignored Sum's protests about not being able to see the pages. Cailan couldn't tell him it was for his own good—that there were creatures out there that might be drawn to the light. Creatures whose attention they really didn't need.

#

Why wasn't Sum stronger? He was nearly eleven!

Why was he so small?

Why was he so weak?

Thoughts tangled in Cailan's mind like the dark, silty weeds from the lake. He tried to focus on the pod. The sky was choked orange above him, under-lit by the heaving incinerators. By the light of his databand, Cailan considered the crack running up the centre of the pod's door panel. It needed replacing, not patching. There had to be something nearby that would do.

He switched off his databand light in case it was too much of a beacon and headed for the closest junk hill, the ground surging beneath him, the stacks pulsing fire in the distance. Cailan's suit struggled to filter enough clean oxygen. In the dimness, he sifted through the waste dropped by years of passing ships. Within a few minutes, despite being careful of his gloves, his hands stung with cuts, and his wrists ached from shifting endless metal detritus.

It was another hour and a half before he finally found something useful—a fragment of an old door panel that just might fit. If he could find another one with seal latches still intact, he should be able to solder them together.

It felt like he'd been out foraging for days; the sky had darkened by the time he made his way back to the pod, two panels in tow. As he trudged, Cailan spotted the suggestion of tracks buried in the red dust and rubble. If only there was a working cart, he wouldn't have to drag the panels a few feet at a time, only pausing to flex his limbs and wait for his suit to clear condensation from his visor.

He had no idea how long he'd been outside, but he hoped Sum had slept through. He prayed Sum woke when he got back.

It took him a moment to realise that a distant movement wasn't condensation clearing. Irregular silhouettes slugged across the hills, away from him—away from the ship. At first he saw two, then five, then more than a dozen. They stopped to examine waste. They dropped objects into their bins and pouches. They shuffled on.

Crouching as low as possible, Cailan heaved the door the last stretch down into the crater, glad he'd switched off his light.

#

Once welded, the two panels would fit the pod doorway. Cailan could have wept. They weren't off Kethell 73 yet, though—not nearly—but it was a start. Better than where they were a few hours ago.

He left the replacement panels against the pod and launched himself into the hull.

"Sum. Hey, Sum! Good news."

Cailan paused in the doorway.

Sum was not on his bunk.

Nor was Sum under his bunk.

Sum wasn't in the hull at all.

Something hot and metallic oozed down the back of Cailan's throat as he realised, with a lurch, that Sum must have gone to the flight deck.

"Sum!" he yelled, shoving through the corridor. Sum had always been stubborn and determined, but Cailan never imagined his little brother would make it to the flight deck with his legs and ribs in such bad shape, otherwise he would have sealed it off. Stupid, stupid.

Cailan burst onto the deck, ready to scream at Sum, ready to haul him away.

Mum Halley and Mum Ella were still there. Of course they were. Mum Ella lay crushed against the control panel, her face turned away so Cailan couldn't see the expression she wore at the last moment, a patch of her hair stained red. Mum Halley was folded at her feet, peaceful but for the odd angle of her body.

There was no Sum.

The shudder and boom of the distant drills quieted, leaving only the slow thud of Cailan's pulse. Backing out of the deck, he wondered if he'd missed Sum in the hull, but deep down he knew he hadn't.

Cailan dragged on his suit, trying not to consider that Sum's small suit still hung on its peg. Breathing wasn't easy with the heat and incinerator pollution, but there was thin, cloying atmosphere outside, so it wasn't impossible for Sum to survive. How he had managed to debark with his injuries, though, Cailan couldn't guess. He tried not to think about the creatures, trawling the planet for waste.

It wasn't just sweat that slicked his face when, after ten minutes, he still hadn't found Sum.

He thought again about the skittish creatures and their relentless trek to the easternmost stack. Had they seen the ship's soft light after all?

Cailan bit out a curse. If he risked leaving the area he would possibly miss Sum. There was barely time left to fix the pod, hardly any painkillers, and he didn't want to think about clean oxygen.

At a loss, Cailan cried, "Sum!" into the reddish mist.

No reply came.

Out of time, Cailan scraped his fingers across his visor, and walked east to the factories and the churning smokestacks above.

#

Heat and dust loaded the air near the stacks. The factories fluted steam and smoke. Cailan tried increasing his helmet's oxygen supply but it did no good; the suit was malfunctioning. Taking shallow breaths, he peered from behind the shell of an old scout truck. Machinists toiled in the factory, sorting, fixing, sending the useless parts to be burnt.

If Sum had come all this way to nerd-out over the creatures, there would be serious trouble. But in his heart, Cailan knew that wasn't true.

A thin stream of mechanical creatures scuttled, clumped, clicked endlessly back and forth. After a while, a smaller figure emerged from the factory, pausing to totter in the entryway. Something metallic glinted at its breast, its hips, its legs, like it was plated. It moved unsteadily forwards.

A scream unfolded in Cailan's throat.

As Sum drew nearer, Cailan staggered out from his hiding spot. The scream choked him, but he gasped, "W-what the hell are you doing?"

Sum couldn't answer. He paused again when Cailan stepped in front of him, but then turned a few inches on the spot and lumbered on.

"Hey, Sum. Don't be an idiot," Cailan said between his teeth. Moisture burned his eyes, blurring everything. Mum Ella and Mum Halley wouldn't want them spending another minute here, and Cailan had had enough; it was time to go. He grasped his brother's wrist and pulled Sum towards the ship, trying not to acknowledge the click, click of Sum's steps behind him. Cailan would not look at him, could not, afraid that if he did he'd fracture like the door he still had to mend. As soon as they slid down into their crater, Cailan pushed Sum into the hull and said, "Just stay put. I have to fix this."

Blinking hard, he turned away, teetering on the edge of delirium, and stumbled to the pod. Cailan wasn't sure who—or what—he was angry at, only that he needed to be angry to stay awake. The work was tough, not because Cailan couldn't weld, but because his hands kept seizing, because dizziness kept sweeping through him.

The orange sky bled to crimson. Black smoke churned above. Metal screamed. Cailan's head rang.

He didn't recall falling to his knees, but they stung where his suit had ripped.

He didn't remember the sky growing so bright, such a brilliant, painful white.

"Boy?"

Cailan clutched the welder. It didn't work anyway. There was no power; hadn't been for ages.

"Boy, can you hear me?" Someone gripped his shoulder.

Cailan stared up at the hazy shape. A woman's face stared down through a visor similar to Cailan's, but for the military insignia carved at the front of her helmet.

"Mum?" Cailan croaked.

The woman shook her head. "Your ship sent up a mayday. Were you aware?" She helped Cailan sit up. "It would have been right before impact." Other people trudged about, also wearing military suits. "If you weren't at the arse-end of nowhere, we would have got here sooner."

Cailan clenched the woman's arm, barely daring to believe she was real.

Rescued.

Could it be true?

"Sum," he said. "Help Sum. He's only little." Cailan wished he hadn't thought those nasty things about Sum, about him being too small and weak.

Two men appeared beside the pod. One addressed Cailan's rescuer. "Ser, the parents are dead. But we found … another boy, in the hull."

Behind them, a short, dark shape tottered. Its mechanical arms flailed out for balance, Sum's head lolling to one side. Because his skull and bones weren't mechanical, they couldn't move like the rest of him, jerky, automatic—as the Machinists had cobbled him together.

"I have to keep him safe." Cailan's voice cracked. "Who'll map the stars?"

One of the men raised an eyebrow at the woman.

"Come on," the woman said to Cailan. "Let's get you off this planet."

"Wait." Cailan clamped his eyes shut, but Sum—or the thing that Sum now was—remained seared to the insides of his eyelids. Cailan prayed Sum had died before the creatures found him and took him east. "Don't leave him here. Not like that."

"We won't leave anyone behind," the woman promised, and she kept her word.

They held a ceremony for Mum Ella, Mum Halley, and Sum. Cailan never asked how they extracted Sum from the machine, only that his remains were laid to rest with their mums.

And even as, a year later, Cailan enrolled in TriForce Academy to train as a medic, his movements always felt a little jerky, a little automatic—as if he were made of machine parts, not flesh and blood.

#

The Machinists toiled, collecting parts from Kethell 73 and crafting creatures of metal and glass and rubber to cart debris to the belching stacks. They were not choosy; anything that came close, anything that passed under them on their giant conveyer belts, anything that could be tailored into efficient, self-sufficient emissaries.

The Machinists created. The Machinists repaired. It was all they knew how to do.