The twins turned their backs on the rainforest and slid into the dark, breezy tunnel under the mountain. Challis hurried behind her brother in silence for a quarter mile before the tunnel ended in a wall pockmarked with balconies and other openings out over the canyon city of Oedolon.

What they could see of Polescos district spread out below in broad sweeps of terraces, ramps, and strips of bare earth that used to be shaded by trellises and curling balustrade trees. Until earlier this year, the looming canyon walls here on the north end of the city had sprouted heavy greenery, with huge folds of the landscape tumbling down like cloth around the scattered windcatchers set into the cliffs, then flattening out at the base where the vegetation was scraped threadbare. Now, the entirety of the walls hung with only thin remnants.

Naked stone skyways soared between the canyon's outcroppings and upcroppings of stone, stretching haphazardly over the city far and thin into the distance until they seemed to simply wisp about like oversized cobwebs.

On this side of a bend in the canyon sat the red stone building blocks of the city's more dirt-hardy occupants. Polescos hunched in cluttered pockets of quavering heat, and Challis could just see the showgrounds still crowded with people for the last few hours of the Pterosaur Exhibition. She tried not to think of the debris left behind by spectators and buyers and sellers from all parts of the city with no regard for those who had to clean it up. Maybe it wouldn't be so bad this time.

"Oh, no." Rasalas had pushed aside the vines covering the opening, but now he stopped to look closely at them. "Feel this, Chall."

She obeyed, running her hands over stretchy, shriveled vines that dropped their leaves at the slightest touch. They still had time, but how long would it be before they dried completely and snapped like twigs beneath her feet?

Challis pushed into the sun and started down the canyon wall with slow, tentative movements while her brother followed. The vines crawled down from high above, a network of handholds and footholds for their trek down, and pillowed them from the hard rock surface. Challis went mostly by feel; she could hardly make sense out of the tangled mess in front of her face. Left foot, right foot. Left hand, right hand. Secure three limbs before replacing the fourth.

She tried to ignore the dislodged clumps of dirt that rained down on her head from Rasalas' boots, but eventually, he spidered off to the side and went on past her. Challis made no attempt to keep up, though even if it mattered the vines just didn't offer her endless pockets of footholds as they did for Rasalas.

He reached the bottom first, dropping onto a walkway running along the canyon wall.

"Close your eyes?" Challis called down. He did, as she could tell by the immediate clarity of her own vision. The ropes congealed into manageable grips, and Challis abandoned her slide-until-something-catches approach for more decisive movements. By now the vines were thinned into dry, naked skeletons that creaked and bent and sprang back into place when she jumped down next to Rasalas. Polescos blurred as Rasalas' view overlapped her own, sliding over her eyes as he opened his.

He led the way down, down to the base of the canyon, passing one windcatcher after another. Unlike the fanned-out flower shape of the turbines blocking the rainforest tunnels, each one in the canyon wall enclosed an egg-shaped space between four wide, curving blades that met on either end. Each was exquisitely ridged and textured to caress every breath of wind, and at specific times of the day these blades would speed along at a blurring rate and send crackling energy along the network set deep into the rock wall.

Challis loved the rounded turbines. She thought about what it would be like to float in the space between the blades and watch the city from within.

Familiar dust was clogging their breath by the time they reached the first buildings and streets of the northernmost region of Polescos. Clanking stacks of equipment for the street vendors dotted the sidewalks. Challis followed closely behind her brother, trying to stay out of the way as the market chattered around them, busy again after the midday hiatus and at the end of the Exhibition. With Rasalas directly in front of her, Challis managed to avoid running into shoppers and children that flashed around her with twice as much flurry as he saw. Sunlight didn't scare the activity from the streets, as empty spaces in the air above individual booths quivered then flickered out into thin films of reflective panels that completely shaded the vendors beneath.

A row of sleek steel one-man crafts stood parked along a side street, lights blinking lazily. Challis and Rasalas slowed their pace as they passed, eyeing the complete lack of wheels while trying to not stare openly. Unlike the box carts and canopy-shaded vehicles they were used to, these were shiny as glass and didn't seem to collect any of the red dust.

"Visitors for the Exhibition." Challis hooked her hand through Rasalas' belt as he maneuvered the foot traffic. A high-pitched trill sounded from a patrolman's whistle in the distance.

"Makes sense," he called back. "Sightseeing before they leave."

"What sights? The empty water fountains?"

Rasalas bumped into someone coming out of a storefront, and something clattered to the pavement. "Sorry, sir," he said, his hands on the other's shoulders to steady them both. Challis bent to pick up the object, almost dropping it when two metal clamps closed around her wrist. She held it out to the man, a wiry little mustache who snatched at the mechanism and tugged it off with practiced efficiency. He looked up to say something but Rasalas had already pulled Challis away. Nobody else gave them more than a sneering glance at their colorless laborers' garb.

Cool mist draped over them as they turned off the main roadway down an avenue. Challis turned her face up toward the pipe system, but even as she did, the rusty pipes sputtered and stopped releasing the cloud of water vapor. The refreshing droplets dissipated into the air. Another dead mister, with not enough water flow to supply it.

The avenue dead-ended at a stone wall. Here, its outer layer of bricks had crumbled into loose heaps, leaving a jagged edge running at an angle from street level almost to the top. The twins clambered up this ledge, feet pushing off familiar steps as they scaled eight feet up and dropped down on the other side onto the crusty sand of one of the famous Polescos pterosaur grounds.

The wall behind them extended in both directions, separating the grounds from the city streets. Inside it, a double row of stables surrounded a courtyard as big around as a racetrack. Most of the time, the area would be scattered with stairstep platforms and equipment racks amid the activity, but over the course of the Exhibition it had been kept clear and open for the displays and demonstrations of the Polescos finest. Now, dust puffed into the air from the clawed feet of pterosaurs as they stamped and flapped at their handlers. One was close, not ten feet away, when it gave a gargling shriek and knocked its huge wing at a saddle rack. The rack rolled smack into the twins, where it deposited a trayful of currying tools onto the sand.

Rasalas and Challis hid a sinking feeling as they met cold gazes from both thrike and handler.

"Teakle," Rasalas said after a moment. Wealthy schoolmate turned adult, Corvin Teakle still had the same dirt-red hair, now pressed flat from his helmet, and high cheekbones that always squinted up his eyes. It could almost be a twitch away from a ready smile, but the twins knew that it was closer to a ready sneer.

Challis crouched, slowly, to scoop up the fallen tools while keeping her eyes on the thrike. In truth, to avoid looking at Corvin. But Corvin was pointedly eyeing her until she straightened again and she had no choice but to face his scowl and swallow stupidly.

"Gannagens," he said.

"Thanks, Chall," Rasalas said, carefully pushing aside the saddle rack and stepping back as another gust of air came from the thrike's wings. "This one's wound up tight. Has it been fed, or will it turn on us?"

"Of course, it has." Corvin had the discretion not to openly roll his eyes at them, though his head lolled the motion anyway. "Headed out to patrol in a few minutes."

Challis, having gotten her nerves under control, lifted her eyebrows at him. "Sorry. We weren't talking about the thrike." At his marvelous expression, she successfully fought down a laugh while her brother had a sudden coughing fit beside her. Corvin glanced to the sides.

"I've gotten worse. From better," he said snidely. Then something snapped in his manner, and he let the tension drop like a bomb. It exploded into a shout. "Where the hell were you?" he raged at Challis, dragging his thrike behind him as he came closer, eyes blazing. "I missed the most important checkpoint in the race because of you! Tofflar was damn near killed taking it on himself because I didn't have my blasted saddle or any of my gear!"

The thrike released a bone-jarring screech that made them all duck back and cover their ears. Corvin spun, hunching his shoulder up against the thrike's nose-thrusting while he fought to keep a tight hold on the lead strap. Rasalas moved sideways so Challis was behind him. Both were on the balls of their feet, ready to move, but held their ground as the thrike jerked savagely toward them.

"Cool it, right now," Rasalas said in a low, harsh tone. "Teakle!"

Challis felt her face flushing hot. Floxogelene particles, or flux, dense in the air and triggered to life by the thrike's activity, buzzed maddeningly in an invisible cloud as Corvin forced the thrike to a standstill. He ended up gripping it around the lower jaw, every muscle clenched tight even as his voice ran soothing and gentle. A slight tremor still carried his words, which Challis expected, as Corvin had every right to be angry at himself and at her. She, however, had nothing to say in defense.

The flux washed over her in a tingling rush, driving at her body to move and her emotions to escalate. She knew that if she gave in to the urges, letting flux both feed her actions and result from them, the vicious cycle would increase the momentum until talking became shouting, dislike swelled into hate, and the situation devolved into survival of the fittest. You could kill or be killed over a trifle in Oedolon, and all it took was a weak conscience. Flux, as everyone in a floxogelene-heavy habitat like a windy canyon learned from a young age, was as hazardous as it was life-giving. Control or be controlled.

With each of them bracing hard against the flux, and the twins finally felt the air settle as Corvin's words turned on them. The soft tone didn't match the subject matter at all. "If you step out of line again, I'll let him at you." He kept stroking the thrike's long beak, not looking at them. "You two had no place anywhere near the races to begin with. If Rib-eye had a lick of sense, he'd assign you to the mud barns with the bucks. Filth enough for you back there."

Challis felt Rasalas' shoulder knotting beneath her palm. She gave him a gentle push to the side and moved up next to him.

"Listen, Teakle," she interrupted his next words before they came out. "I'm sorry, okay? I'm sorry I didn't get your equipment. I'll make sure Rib-eye doesn't take anything out on you for what happened."

"He better not," Corvin said, but the fire dwindled out of his tone. There was only a trace of stung pride of one of Polescos' best racers for missing out on his performance.

"Gannagens!"

Both looked toward the shout from the far side of the courtyard, where someone was signaling them to come. Corvin pulled his thrike away with a smug look.

Forge was twisting the handle of a pitchfork on the toe of his boot, all while tapping his foot on the sand. As the Gannagens approached, he leaned the pitchfork against a doorway and fingered the crop at his belt.

"There you are. The state of this place," he growled. "Looks like it hasn't seen fresh padding for a week." Forge, or Rib-eye as he was known by his employees, was a man whose work as stablemaster scar-streaked his skin as mottled pink as a healthy steak and kept him as limber as a man in his forties, though rumor had it that he was well past ninety. Surrounded by the whirling flux fields activated by the pterosaurs, Rib-eye lived in a state of constant recharging and had so far refused to sink into the stillness and slowness of age. Such was the world in which you stopped moving to stop living.

He managed to keep scowling as he took a long drink from a fizzing canteen while they watched. "We haven't heard the end of that stunt from earlier. If I catch either of you messing with one of those prize pterosaurs again for a week, I'll whup you halfway to hell before you even think about hiding it from me. What do I need to do, keep you on a leash?"

"We're here now, aren't we?" Rasalas matched his tone. "It's not something that –"

Challis interrupted. "We'll handle it, sir. Just recuperating after all the action."

She could just see the heavier pulse of her brother's neck patch. Corvin's words had cut deeper into Rasalas than into her, and all propriety toward their boss was now gone – the first rule being 'Don't make it worse'. It was rough enough. Forge gave a disgusted sniff and jerked his head toward the mud barns behind the prize thrike stables.

"Buck's stuck on his way out," he said. "Standstill about an hour ago. Once that's done, I want all the show stalls clean and shiny by twelfth bell. Then you'll meet Scat at the showgrounds and get to work. Now go, I have a job to do."

He started to swagger past them but stopped at a low mutter from Rasalas.

"Problem?" he asked quietly.

The other met his eyes, trying to hide a smile. "I thought tormenting us was your job."

Forge’s hand flashed up to cuff him upside the head. "Mud barn. Go!"

Challis pulled her brother around the corner. "You're just asking for it," she whispered when they were out of earshot.

Rasalas still wore a saucy grin. "Um, so were you. With Corvin."

"Teakle's an idiot. Choose your battles."

The mud barns had a roof but no outer wall, aside from a lip eighteen inches high around the edges to keep in the baby bucks and the mud. At any time of year there were usually one or two bucks clumsily legging around, squeaking miniatures of the big stamping creatures. Fickle as they were with their riders, adult thrikes tended to show little care for their babies after weaning them. Perhaps this was an unexpected result of constant human companionship and care, but the high-level energy potential of thrikes clearly kept their attention spans as short as their tempers. Challis stepped over the rim and glanced around. Someone was in the shade on the far end of the barn, carefully mudding a baby buck's hide to keep the flies away and regulate the little one's body temperature, but no less than five people crowded at the gate of the first stall on the right. They were not in laborer's garb, and were chatting away as if in a public square.

"Let her in," Rasalas called, reaching in between the elbows and shoulders to clack open the gate for Challis. He remained outside away from the others, leaning his head back to close his eyes until his sister had seen everything she needed to.

Challis looked over a dimly lit square of mud scattered with leaves. One other laborer was inside, but the massive body of a thrike dominated the space.

It turned an eye onto her, its toothy beak snapping open and shut once like a crocodile's. A long, graceful neck twitched with muscle where it met protruding shoulder blades at the base of its wing. While reclining fatly on its side, the thrike kept these wings folded into long sheaves next to its body, though Challis knew it had over six yards of wingspan. This one was the glossy blond of fresh wood chips, tipped with black on its beak and tail, and caked with a layer of mud on the swollen underbelly.

As she watched, the thrike stiffened and strained once, the claws of one leg squelching into the mud. A wing bent forward to reveal a tiny, clawed joint halfway along its length that the thrike used to push itself into a useless twist. Low grunts rumbled along the ground and reverberated in Challis' knees. Then she noticed the dark spill of substance coating the thrike's back legs. She turned to the boy in the corner of the stall.

"How long since she popped?"

He stopped scrubbing the inside of a steel basin and blew out a breath in thought, his tired eyes on the laboring animal. "Two hours? Maybe three."

"What's with all the attention?"

"Just part of the Exhibition," he said with a shrug, not bothering to lower his voice. "Why anyone pays for a ticket and then spends time back here is beyond me."

Challis nodded. She got down on her knees and, praying that a twenty-inch razor beak wouldn't start stabbing her skull, felt along the thrike's bulge. A buck was twiggy and bony at birth, with multiple protrusions that could get stuck in its mother's uterine wall on the way out. Challis rubbed slowly down the outside of the contracting hide, the sandpaper surface tight and sticky beneath her fingers.

"Fill that basin up, will you?" she said to the laborer, who looked awfully young and thready. "As full as you can carry. And I'll need some lather. Ras?"

The boy pushed his way out the gate, and in a moment Challis heard Rasalas' voice. "Here."

Both her hands were pressed to the thrike's underbelly now, he saw, though her face was toward the wall as she was completely relying on feel. The sharp, peppery odor got stronger as he drew up close to the gate. Rasalas blew out a breath. Only once in the last six years had Challis made him actually come inside to help, and he wasn't eager to do it again. Especially with a crowd of prying strangers watching with only a scholarly interest in the situation.

"Find Corvin, quickly," Challis said to him. "Or someone else who's just been flying. Make sure they've got their uniform."

Something in the tone of her voice sent Rasalas out at a run. Sunlight spun over Challis' vision as her brother raced across the courtyard, his head on a swivel.

Trying to ignore the noisy presence of the onlookers, Challis straightened and pulled off her belt to tie the lower leg of the thrike in a tightened noose. That would simplify things anyway. She took a deep breath in, letting the heavy tang of the air settle into her lungs and force them to become accustomed to it. Thrike nests were always smelly, but today she could almost feel the stench of fresh mud and gluey fluids shriveling her nose and mouth into jerky.

The boy returned, lugging the basinful of water from the only functional pump in the corner of the barn. Warmth splashed onto Challis' knees as she rolled up her sleeves as high as they would go, then plunged her arms into the basin. The boy handed her the lather, and Challis gave her skin a brisk minute of scrubbing until her knuckles and elbows were tingling. Not tingly enough. She closed her eyes, looking for Rasalas, and saw the dark outline of the barns swing into view. His hand flashed up over his face, wiping sweat or hair from his forehead, and a moment later Challis heard him outside.

"Oh, get over yourself," he panted to someone, then, "Got Tofflar here, Chall. How can we help?"

The spectators quieted when Thax and Rasalas arrived, as if just realizing something was unusual. Only Thax's muttering was audible in the silence.

"Holy crickets above," he said. "I swear, if this is just a rotten joke to get me into mudwrestling, I'll bury you behind the –"

"I need your jacket," Challis broke in. "Still powered up, right?"

"What, why?"

"We've got two thrikes in the danger zone and I'm not getting fired just because you were too stubborn to help. Please, Thax."

"It's 'Captain'," he sighed, but shrugged out of the fine quilted jacket. Complex punchcord lining crisscrossed the chest and throat and ran down the arms to double wrap the wrists: the places where moving air currents were easily caught and held in a state of potential energy. Challis took the jacket and, without hesitation, dunked it into the tub of water. She rubbed roughly at the lining until the fizzing vibrations leached out of the punchcord and into the tub in a crackling cloud. Something kept pounding through her head, something about flux molecules when they were exposed to heavy water. It had to work.

Amid the sloshing she barely heard Thax's outbursts of dismay, but she ignored them. Rasalas could handle him.

She lobbed the dripping jacket off to the side, its quilted surface beading up the water and its lining flat and lifeless. Hot prickles shocked up and down her skin as she submerged her arms in the tub again. The belt tugged from where she had it pinned down by her knee, and another guttering rumble came from the thrike as it strained and twisted.

"What are you doing?" the voice of the other laborer sounded next to her. Challis finally remembered his name, Wellis, and spoke in a rush as she repositioned herself.

"Buck's stalled and overall bloodrush is pulsing too weakly at the birth channel. This mother's still too young to have much of a constant charge in her circulation, so I'm going to get in there and give things a tug along."

"And the flux?"

"This supercharged water could be enough to reactivate the channel and strengthen the contractions," Challis said in a voice that sounded far more certain than she felt. "Short of shooting water straight up the poor animal or plopping her in a tub, it's the best I can think of."

Wellis stared at her, then at the thrike, face stuck in a grimace. Challis huffed. This boy was too young to be the only one on duty. "You going to try to stop me, or are you going to come around and keep her claws out of my face?"

"Oh." He jumped to the other side of her and clasped his hands around the thrike's leg that wasn't belted down. Challis bent, twisted, and ended up completely bellying the mud. It squelched warmly through her shirt and trousers. One arm, her left, braced herself while the other was swallowed up past her elbow in the birth canal of the thrike.

Sweat flashed hot onto her face as she felt around. The flux, fresh from Tofflar's jacket, buzzed wetly against her compressed arm. Maybe it would be enough to help speed things along naturally, or maybe it was too late already. With another breath of determination, she pushed in just a little farther, and found a blunt, ribbed little structure under her fingers. She took hold of it and dug her other hand harder into the mud to adjust her angle.

Then a violent pressure squeezed around her fist for a few seconds, tightly enough to make Challis gasp. A distant part of her brain reminded her to relax her muscles, and the same part realized that the flux was helping, perhaps too well.

"What in the good earth ­–" a voice rumbled loudly over the murmurings.

Challis had her eyes shut in concentration. She would have noticed that the voice belonged to Rib-eye, and would have withheld her gritted response, except that something had just snapped at her submerged knuckles, twice. Like tiny teeth. What was it that Rasalas had said about her having the nerve for this? She was almost shaking out of her skin. But she couldn't stop now. She tilted her face up toward Wellis.

"Did you know," she puffed, her tone trying for casual, "that there are two of them in there?"

His mouth dropped open.

Challis regained her grip on the little ribbed crest of the first buck, and after the next pulse, pushed it a few inches further inside before hauling it toward her with all her strength. The mighty tug slurked out the body of a buck, a hot little package of bones and belly that lumped its way out and collapsed on top of Challis. She lifted the armful and struggled up to her knees to plop the buck into the basin of water. "Yours, Wellis," she said, dropping back onto her stomach. "I'll get the next."

Wellis dove over to support the baby buck, clear its airway, and scrub it fresh in the energy-packed water. Challis reached in again alongside the thick cord still trailing from the buck. She pushed in almost as far as her shoulder this time, and snagged the same little beak that had tried to nip her hand earlier. Baby Two was almost thrashing in excitement as Challis pulled again with an effort that pressed her lungs flat. Another package fell sloppily into Challis' arms. This time it was harder to get up onto her knees, as the thrike weighed as much as a chunky human toddler, but she managed to heave it over the rim of the basin with a splash of relief. She and Wellis dodged the little snapping beak and batlike wings as they scrubbed, dried, and wrapped up the second baby buck in cloth. They snapped cords and deposited all the messy bits into another bucket. The last thing they did was to tip the whole washbasin over the mother thrike so the leftover flux would soak into her muddy hide and begin repairing tissue damage. Adrenaline was still trembling through Challis' arms when she sat back against the wall to breathe.

The onlookers had begun clapping, or maybe they'd been going for a while. Challis didn't look at them. She dimly realized that Forge was talking, but his words were just a blur over the numb expanse of how little she cared. Sweat dripped into her mouth, and her muscles were objecting to the over-excited thump of her heartbeat. Especially the right arm, the one that had dragged two new thrikes into the world. Twins. That was rare enough for domesticated thrikes, so rare that…

Challis sat up in a flash when Wellis called her name, as if repeating himself. Her double vision prevented her from seeing his expression clearly in the dimness of the barn, but his words confirmed her fear.

"Lost one."

She stared at the cloth-wrapped armful. Two inches of pale beak were visible against Wellis' brown shirt, and the short little tail drooped over one wrist. Everything was still.

Then the gate crashed open and Rasalas thudded down beside them.

"Give it to me," he said, seizing the unmoving buck out of Wellis' arms. He was crouched over it in the center of the puddle, alternating pumping at its chest and rubbing its body with the cloth, before Challis fully realized what was happening. His harsh whispers seemed the only sound in the world as he fought the unstoppable.

"Gannagen." The voice smacked down like a mallet to the mud. The spectators had disappeared, and only Forge stood outside the gate. He was looking at Rasalas but snapped his attention down onto Challis when she looked wearily up at him. "It's past tenth bell already," he said, but Challis didn't miss the fact that his tone was less accusing than usual, if only by a fraction. "Patrol will be back soon. You've got to go muck out those show stalls."

Rasalas didn't stop. "They can wait," he said, every word punctuated with a firm push at the baby thrike. "This can't."

Challis chilled when Forge straightened, just a bit.

"I must have misheard that, Gannagen."

Rasalas glanced at him, just for a second, before starting up again as determined as before without a word. Challis got noisily to her feet and leaned a hand on the wall. Her eyes were on Forge, but through her brother's eyes she could see the sprawled little body. Something seemed wrong with its neck, even as Rasalas tried to reposition it between compressions.

"We'll handle it, sir," she said, unable to look away. "He's just trying to fix what I've broken." She sighed. "Again."