"Barking spiders!" the young boy next to her whispered. He was nearly as tall as her, and his short blond hair stuck straight up into the air. "I'd hate to see those two get loose."

Deryn resisted the urge to explain that lupines were the tamest of the fabs. Wolves were really just a kind of dog, and could be trained almost as easily. Airbeasts came from trickier stock, of course.

When no one stepped forward to admit their fear, the flight captain said, "Excellent. Then you won't mind a closer look."

The driver's whip snapped again, and the carriage rumbled across the broken field, the nearest tiger passing within arm's reach of the volunteers. The snarling beasts were too much for three boys at the other end of the line. They broke ranks and ran shrieking back toward the open gates of the Scrubs.

Deryn kept her eyes focused directly ahead as the tigers passed, but a whiff of them - a mix of wet dog and raw meat - sent shivers down her spine.

"Not bad, not bad," the flight captain said. "I'm glad to see so few of our young men succumbing to common superstition."

Deryn snorted. A few people - Monkey Luddites, they were called - were afraid of Darwinist beasties on principle. They thought that crossbreeding natural creatures was more blasphemy than science, even if fabs had been the backbone of the British Empire for the last fifty years.

She wondered for a moment if these tigers were the secret test Jaspert had warned her about, and smirked. If so, it had been a pure dawdle.

"But your nerves of steel may not last the day, gentlemen," the flight captain said. "Before moving on we'd like to discover if you have a head for heights. Coxswain?"

"About-face!" shouted an airman. With a muddled bit of shuffling, the line of boys turned itself about to face the hangar tent. Deryn saw that Jaspert was still here, hanging off to one side with the boffins. They were all wearing clart-snaffling grins.

Then the hangar's tent flaps split apart, and Deryn's jaw dropped open... .

An airbeast was inside: a Huxley ascender, its tentacles in the grips of a dozen ground men. The beast pulsed and trembled as they drew it gently out, setting its translucent gasbag shimmering with the red light of the rising sun.

"A medusa," gasped the boy next to her.

Deryn nodded. This was the first hydrogen breather ever fabricated, nothing like the giant living airships of today, with their gondolas, engines, and observation decks.

The Huxley was made from the life chains of medusae -  jellyfish and other venomous sea creatures - and was practically as dangerous. One wrong puff of wind could spook a Huxley, sending it diving for the ground like a bird headed for worms. The creatures' fishy guts could survive almost any fall, but their human passengers were rarely so lucky.

Then Deryn saw a pilot's rig hanging from the airbeast, and her eyes widened still farther.

Was this the test of "air sense" Jaspert had been hinting at? And he'd let her believe he'd only been kidding! That bum-rag.

"You lucky young gents will be taking a ride this morning," the flight captain said from behind them. "Not a long one: only up a thousand feet or so and then back down ... after ten minutes lofting in the air. Believe me, you'll see London as you never have before!"

Deryn felt a smile creeping across her lips. Finally, a chance to see the world from on high again, just like in one of Da's balloons.

"To those of you who'd prefer not to," the flight captain finished, "we bid fond farewells."

"Any of you little blighters want out?" shouted the coxswain from the end of the line. "Then get out now! Otherwise, it's skyward with you!"

After a short pause another dozen boys departed. They didn't run screaming this time, just slunk toward the gates in a huddled pack, a few pale and frightened faces glancing back at the pulsing, hovering monster. Deryn realized with pride that almost half the volunteers were gone.

"Right, then." The flight captain stepped in front of the line. "Now that the Monkey Luddites have been cleared out, who'd like to go first?"

Without hesitation, without a thought of what Jaspert had said about not drawing attention, and with the last squick of nerves in her belly gone, Deryn Sharp took one step forward.

"Please, sir. I'd like to fly."

The pilot's rig held her snugly, the contraption swaying gently under the medusa's body. Leather straps passed under her arms and around her waist, then were clipped to the curved seat that she perched on like a horseman riding sidesaddle. Deryn had worried that the coxswain would discover her secret as he buckled her in, but Jaspert had been right about one thing: There wasn't much to give her away.

"Just ride it up, laddie," the man said quietly. "Enjoy the view and wait for us to pull you down. Most of all, don't do anything to upset the beastie."

"Aye, sir." She swallowed.

"If you start to panic, or if you think something's gone wrong, just throw this." He pressed a thick roll of yellow cloth into her hand, then tied one end around her wrist. "And we'll wind you down steady and fast."

Deryn clutched it tightly. "Don't worry. I won't panic."

"That's what they all say." He smiled, and pressed into her other hand a cord leading to a pair of water bags harnessed to the creature's tentacles. "But if by any chance you do anything completely stupid, the Huxley may go into a dive. If the ground's coming up too fast, just give this a tug."

"It spills the water out, making the beast lighter," Deryn said, nodding. Just like the sandbags on Da's balloons.

"Very clever, laddie," the coxswain said. "But cleverness is no substitute for air sense, which is Service talk for keeping your barking head. Understand?"

"Yes, sir," Deryn said. She couldn't wait to get off the ground, the flightless years since Da's accident suddenly heavy in her chest.

The coxswain stepped back and blew a short pattern on his whistle. As the final note shrieked, the ground men let go of the Huxley's tentacles all together.

The straps cut into her as the airbeast rose, like being scooped up in a giant net. A moment later the feeling of ascent vanished, as if the earth itself were dropping away... .

"ASCENDING."

Down below, the line of boys stared up in undisguised awe. Jaspert was grinning like a loon, and even the boffins' faces showed squicks of fascination. Deryn felt brilliant, rising through the air at the center of everyone's attention, like an acrobat aloft on a swing. She wanted to make a speech:

"Hey, all you sods, I can fly and you can't! A natural airman, in case you haven't noticed. And in conclusion, I'd like to add that I'm a girl and you can all get stuffed!"

The four airmen at the winch were letting the cable out quickly, and soon the upturned faces blurred with distance. Larger geometries came into view: the worn curves of an old cricket oval on the ascension field, the network of roads and railways surrounding the Scrubs, the wings of the prison pointing southward like a huge pitchfork.

Deryn looked up and saw the medusa's body alight with the sunrise, pulsing veins and arteries running like iridescent ivy through its translucent flesh. The tentacles drifted in the soft breezes around her, capturing pollen and insects and sucking them into the stomach sack above.

Hydrogen breathers didn't really breathe hydrogen, of course. They exhaled it: burped it into their own gasbags. The bacteria in their stomachs broke down food into pure elements - oxygen, carbon, and, most important, lighter-than-air hydrogen.

It should have been nauseating, Deryn supposed, hanging suspended from all those gaseous dead insects. Or terrifying, with nothing but a few leather straps between her and a quarter mile of tumbling to a terrible death. But she felt as grand as an eagle on the wing.

The smoky outline of central London rose up toward the east, divided by the winding, shimmering snake of the River Thames. Soon she could make out the green expanse of Hyde Park and Kensington Gardens. It was like looking down on a living map: the omnibuses crawling along like bugs, sailboats fluttering as they tacked against the breeze.

Then, just as the spire of St. Paul's Cathedral rose into view, a shiver passed through the rig.

Deryn scowled. Were her ten minutes up already?

She looked down, but the line leading to the ground hung slack. They weren't reeling her in just yet.

The jolt came again, and Deryn saw a few of the tentacles around her clench, coiling like ribbons scraped between a pair of scissors. They were slowly gathering back into a single strand.

The Huxley was nervous.

Deryn swung herself from side to side, ignoring the majesty of London to search the horizon for whatever was spooking the airbeast.

Then she spotted it: a dark shapeless mass in the north, a rolling wave of clouds spreading across the sky. Its leading edge crept forward steadily, blackening the northern suburbs with rain.

Deryn felt the hairs on her arms tingling.

She dropped her gaze to the Scrubs, wondering if the tiny airmen down there could see the storm front too, and would start to reel her in. But the proving ground still glowed with light from the rising sun. From down there they would see only clear skies above, as cheery as a picnic.

Deryn waved a hand. Could they even see her well enough? But of course they'd only think she was larking about.

"Bum-rag!" she swore, and glared at the roll of yellow cloth tied to her wrist. A real ascender scout would have semaphore flags, or at least a message lizard that could scamper down the line. But all they'd given her was a panic signal.

And Deryn Sharp was not panicking!

At least, she didn't think she was... .

She stared at the blackness in the sky, wondering if it were only a last bit of night the sunrise hadn't chased away. What if she had no air sense at all, and the height had gone to her head?

Deryn closed her eyes, took a deep breath, and counted to ten.

When she opened them again, the clouds were still there - closer.

The Huxley trembled again, and Deryn smelled lightning in the air. The approaching squall was definitely real. The aerology manual had been right after all: Red sky in morning, sailors take warning.

She stared again at the yellow cloth. If the officers below saw it unfurl, they'd think she was panicking. Then she'd have to explain that it hadn't been terror, just a coolheaded observation that rough weather was coming. Maybe they'd commend her for making the right decision.

But what if the squall changed course? Or faded to a drizzle before it arrived at the Scrubs?

Deryn clenched her teeth, wondering how long she'd been up here. Weren't ten minutes almost up? Or had her sense of time gone crook in the vast, cold sky?

Her eyes darted back and forth between the rolled-up yellow cloth and the approaching storm, wondering what a boy would do.

FIVE

When Prince Aleksandar awoke, his tongue was coated with sickly sweetness. The awful taste overpowered his other senses; he couldn't see or hear or even think, as if his brain were drenched in sugary brine.

Gradually his head cleared - he smelled kerosene and heard tree branches thrashing past outside. The world rocked dizzily around him, hard-edged and metallic.

Then Alek began to remember: the midnight piloting lesson, his teachers turning on him, and finally the sweet-smelling chemical that had knocked him out. He was still in the Stormwalker, still moving away from home. All of it had really happened... . He'd been kidnapped.

At least he was still alive. Maybe they planned to ransom him. Humiliating, he supposed, but better than dying.

His kidnappers evidently didn't think Alek was much of a threat. They hadn't tied him up. Someone had even thought to put a blanket between him and the rocking metal floor.

He opened his eyes and saw shifting patches of light, a grid of swaying shadows cast by a ventilation grill. Neat racks of explosive shells lined the walls, and the hiss of pneumatics was louder than ever. He was in the belly of the Stormwalker - the gunners' station.

"Your Highness?" came a nervous voice.

Alek pulled himself up from the blanket, squinting through the darkness. One of the crewmen sat bolt upright against a rack of shells, wide-eyed and at attention. Traitor or not, the man probably had never been alone with a prince before. He didn't look much older than twenty.

"Where are we?" Alek said, trying to use the steely tone of command his father had taught him.

"I ... suppose I don't know exactly, Your Highness."

Alek frowned, but the man had a point. There wasn't much to see down here except through the gun sight of the 57-millimeter cannon. "Where are we headed, then?"

The crewman swallowed, then reached a hand up toward the communicating hatch. "I'll get Count Volger."

"No," Alek snapped, and the man froze.

Aleksandar smiled grimly. At least someone in this machine remembered his station.

"What's your name?"

The man saluted. "Corporal Bauer, sir."

"All right, Bauer," he said in a calm, even voice. "I'm ordering you to let me go. I can drop out the belly hatch while we're still moving. You can follow and help me get home. I'll make sure my father rewards you. You'll be a hero, instead of a traitor."

"Your father ..." The man's face fell. "I'm so sorry."

Like a long echo rolling in from a distance, Alek's mind replayed what Count Volger had said as the chemical had taken hold - something about his parents being dead.

"No," he said again, but the tone of command was gone. Suddenly the metal confines of the Stormwalker's belly felt crushingly small. In his own ears Alek's voice sounded broken now, like a child's. "Please let me go."

But the man looked away, embarrassed, reaching up to rap on the hatchway with an oily wrench.

"Your father made preparations before he left for Sarajevo," Count Volger said. "In case the worst happened."

Alek didn't answer. He was staring out the Stormwalker's viewport from the commander's chair, watching the tops of young hornbeam trees roll past. Beside him Otto Klopp guided the machine with steady, perfect motions of the saunters.

Dawn was breaking, the horizon turning bloodred. They were still deep in the forest, heading west on a narrow carriage path.

"He was a wise man," Klopp said. "He knew that going so close to Serbia would be dangerous."

"But threats couldn't keep the archduke from his duty," Count Volger said.

"Duty?" Alek held his throbbing head; he could still taste the chemicals in his mouth. "But my mother ... He would never take her into danger."