Finally the pine branches cleared before them, and Klopp said, "Turn here and we'll have better footing, young master."

"Isn't this one of Mother's riding paths?" Alek said. "She'll have my hide if we track it up!" Whenever one of Princess Sophie's horses stumbled on a walker footprint, Master Klopp, Alek, and even Father felt her wrath for days.

But he eased back on the throttle, grateful for a moment of rest, bringing the Stormwalker to a halt on the trail. Inside his piloting jacket Alek was soaked with sweat.

"Disagreeable in every way, Your Highness," Volger said. "But necessary if we're to make good time tonight."

Alek turned to Otto Klopp and frowned. "Make good time? But this is just practice. We're not going anywhere, are we?"

Klopp didn't answer, his eyes glancing up at the count. Alek pulled his hands from the saunters and swiveled the pilot's chair around.

"Volger, what's going on?"

The wildcount stared down at him in silence, and Alek felt suddenly very alone out here in the darkness.

His mind began to replay his father's warnings: How some nobles believed that Alek's muddled lineage threatened the empire. That one day the insults might turn into something worse... .

But these men couldn't be traitors. Volger had held a sword to his throat a thousand times in fencing practice, and his master of mechaniks? Unthinkable.

"Where are we going, Otto? Explain this at once."

"You're to come with us, Your Highness," Otto Klopp said softly.

"We have to get as far away from Prague as possible," Volger said. "Your father's orders."

"But my father isn't even ..." Alek gritted his teeth and swore. What a fool he'd been, tempted into the forest with tales of midnight piloting, like luring a child with candy. The whole household was asleep, his parents away in Sarajevo.

Alek's arms were still tired from fighting to keep the Stormwalker upright, and strapped into the pilot's chair he could hardly draw his knife. He closed his eyes - he'd left the weapon back in his room, under the pillow.

"The archduke left instructions," Count Volger said.

"You're lying!" Alek shouted.

"I wish we were, young master." Volger reached into his riding jacket.

A surge of panic swept into Alek, cutting through his despair. His hands shot to the unfamiliar controls, searching for the distress whistle's cord. They couldn't be far from home yet. Surely someone would hear the Stormwalker's shriek.

Otto jumped into motion, grabbing Alek's arms. Volger swept a flask from his jacket and forced its open mouth to Alek's face. A sweet smell filled the cabin, sending his mind spinning. He tried not to breathe, struggling against the larger men.

Then his fingers found the distress cord and pulled -

But Master Klopp's hands were already at the controls, spilling the Stormwalker's pneumatic pressure. The whistle let out only a miserable descending wail, like a teakettle pulled from the fire.

Alek still struggled, holding his breath for what felt like minutes, but finally his lungs rebelled. He scooped in a ragged breath, the sharp scent of chemicals filling his head ...

A cascade of bright spots fell across the instruments, and a weight seemed to lift from Alek's shoulders. He felt as though he were floating free of the men's grasp, free of the seat straps - free of gravity, even.

"My father will have your heads," he managed to croak.

"Alas not, Your Highness," Count Volger said. "Your parents are both dead, murdered this night in Sarajevo."

Alek tried to laugh at this absurd statement, but the world twisted sideways under him, darkness and silence crashing down.

THREE

"Wake up, you ninny!"

Deryn Sharp opened one eye ... and found herself staring at etched lines streaming past an airbeast's body, like a river's course around an island - an airflow diagram. Lifting her head from the aeronautics manual, she discovered that the open page was stuck to her face.

"You stayed up all night!" The voice of her brother, Jaspert, battered her ears again. "I told you to get some sleep!"

Deryn gently peeled the page from her cheek and frowned - a smudge of drool had disfigured the diagram. She wondered if sleeping with her head in the manual had stuffed still more aeronautics into her brain.

"Obviously I did get some sleep, Jaspert, seeing as you found me snoring."

"Aye, but not properly in bed." He was moving around the small rented room in the darkness, piecing together a clean airman's uniform. "One more hour of studying, you said, and you've burnt our last candle down to a squick!"

Deryn rubbed at her eyes, looking around the small, depressing room. It was always damp and smelled of horse clart from the stables below. Hopefully last night would be the last time she slept here, in bed or not. "Doesn't matter. The Service has its own candles."

"Aye, if you pass the test."

Deryn snorted. She'd studied only because she hadn't been able to sleep, half excited about finally taking the airman middy's test, half terrified that someone would see through her disguise. "No need to worry about that, Jaspert. I'll pass."

Her brother nodded slowly, a mischievous expression crossing his face. "Aye, maybe you're a crack hand with sextants and aerology. And maybe you can draw any airbeast in the fleet. But there's one test I haven't mentioned. It's not about book learning - more what they call 'air sense.'"

"Air sense?" Deryn said. "Are you winding me up?"

"It's a dark secret of the Service." Jaspert leaned forward, his voice dropping to a whisper. "I've risked expulsion for daring to mention it to a civilian."

"You are full of clart, Jaspert Sharp!"

"I can say no more." He pulled his still-buttoned shirt over his head, and when his face emerged, it had broken into a smile.

Deryn scowled, still not sure if he was kidding. As if she weren't nervous enough.

Jaspert tied his airman's neckerchief. "Get your slops on and we'll see what you look like. All that studying's going to waste if your tailoring don't persuade them."

Deryn stared sullenly down at the pile of borrowed clothes. After all her studying and everything she'd learned when her father was alive, the middy's test would be easy. But what was in her head wouldn't matter unless she could fool the Air Service boffins into believing her name was Dylan, not Deryn.

She'd resewn Jaspert's old clothes to alter their shape, and she was plenty tall - taller than most boys of midshipman's age. But height and shape weren't everything. A month of practicing on the streets of London and in front of the mirror had convinced her of that.

Boys had something else ... a sort of swagger about them.

When she was dressed, Deryn gazed at her reflection in a darkened window. Her usual self stared back: female and fifteen. The careful tailoring only made her look queerly skinny, not so much a boy as some tattie bogle set out in old clothes to scare the crows.

"Well?" she said finally. "Do I pass as a Dylan?"

Jaspert's eyes drifted up and down, but he said nothing.

"I'm plenty tall for sixteen, right?" she pleaded.

Finally he nodded. "Aye, I suppose you'll pass. It's just lucky you've no diddies to speak of."

Deryn's jaw dropped open, her arms crossing over her chest. "And you're a bum-rag covered in clart!"

Jaspert laughed, slapping her hard on the back. "That's the spirit. I'll have you swearing like a navy lad yet."

The London omnibuses were much fancier than those back in Scotland - faster, too. The one that took them to the airship field at Wormwood Scrubs was drawn by a hippoesque the breadth of two oxen across the shoulders. The huge, powerful beast had them nearing the Scrubs before dawn had broken.

Deryn stared out the window, watching the movements of treetops and windblown trash for hints about the day's weather. The horizon was red, and the Manual of Aerology claimed, Red sky in morning, sailors take warning. But Da had always said that was just an old wives' tale. It was when you saw a dog eating grass that you knew the heavens were about to split.

Not that a drop of rain mattered - the tests today would be indoors. It was book learning the Air Service demanded from their young midshipmen: navigation and aerodynamics. But staring at the sky was safer than reading the glances of the other passengers.

Since getting on the bus with Jaspert, Deryn's skin had itched with wondering what she looked like to strangers. Could they see through her boy's slops and shorn hair? Did they really think she was a young recruit on his way to the Air Proving Ground? Or did she look like some lassie with a few screws loose, playing dress-up in her brother's old clothes?

The omnibus's next to last stop was at the Scrubs' famous prison. Most of the passengers disembarked there, women carrying lunch pails and gifts for their men inside. The sight of barred windows made Deryn's stomach churn. How much trouble would Jaspert be in if this ruse went wrong? Enough to lose his position in the Service? To send him to jail, even?

It just wasn't fair, her being born a girl! She knew more about aeronautics than Da had ever crammed into Jaspert's attic. On top of which, she had a better head for heights than her brother.

The worst thing was, if the boffins didn't let her into the Service, she'd be spending tonight in that horrible rented room again, and headed back to Scotland by tomorrow.

Her mother and the aunties were waiting there, certain that this mad scheme wouldn't work and ready to stuff Deryn back into skirts and corsets. No more dreams of flying, no more studying, no more swearing! And the last of her inheritance wasted on this trip to London.

She glared at the three boys riding in the front of the bus, jostling each other and giggling nervously as the proving ground drew closer, happy as a box of birds. The tallest hardly came up to Deryn's shoulder. They couldn't be so much stronger, and she didn't credit that they were as smart or as brave. So why should they be allowed into the king's service and not her?

Deryn Sharp gritted her teeth, resolving that no one would see through her disguise.

There couldn't be that much trick to it, being a stupid boy.

The line of recruits on the ascension field weren't impressive. Most looked barely sixteen, sent off by their families to find fortune and advancement. A few older boys were mixed in with the others, probably middies coming over from the navy.

Looking at their anxious faces, Deryn was glad to have had a father who'd taken her up in hot-air balloons. She'd seen the ground from on high plenty of times. But that didn't keep her nerves from playing up. She almost reached for Jaspert's hand before realizing how that would look.

"All right, Dylan," he said quietly as they neared the desk. "Just remember what I told you."

Deryn snorted. Last night Jaspert had demonstrated how a proper boy checked his fingernails - looking at his palm, fingers bent, whereas girls looked at the backs of their hands, fingers splayed.

"Aye, Jaspert," she said. "But if they ask me to do my nails, don't you think the jig's up already?"

He didn't laugh. "Just don't draw attention to yourself, right?"

Deryn said nothing more, following him to the long table set up outside a white hangar tent. Three officers sat behind it, accepting letters of introduction from the recruits.

"Ah, Coxswain Sharp!" one said. He wore the uniform of a flight lieutenant, but also the curve-brimmed bowler hat of a boffin.

Jaspert saluted him smartly. "Lieutenant Cook, may I present my cousin Dylan."

When Cook held out his hand to Deryn, she felt the moment of British pride that boffins always gave her. Here was a man who'd reached into the very chains of life and worked them to suit his purposes.

She gave his hand the firmest shake she could. "Nice to meet you, sir."

"Always a pleasure to meet a Sharp fellow," the boffin said, then chuckled at his own joke. "Your cousin speaks highly of your comprehension of aeronautics and aerology."

Deryn cleared her throat, using the soft, low voice she'd been practicing for weeks. "My da - that is, my uncle - taught us all about ballooning."

"Ah, yes, a brave man." He shook his head. "A tragedy he isn't here to see the triumphs of living flight."

"Aye, he would've loved it, sir." Da had gone up in only hot-air balloons, not hydrogen breathers like the Service used.

Jaspert gave her a nudge, and Deryn remembered the letter of recommendation. She pulled it from her jacket and offered it to Flight Lieutenant Cook. He pretended to study it, which was silly because he'd written it himself as a favor to Jaspert, but even boffins had to follow Royal Navy form.

"This seems to be in order." His eyes drifted up from the letter and traveled across Deryn's borrowed outfit, looking troubled for a moment by what he saw.

She stood stiffly under his gaze, wondering what she'd done wrong. Was it her hair? Her voice? Had the handshake somehow gone amiss?

"Bit spindly, aren't you?" the boffin finally said.

"Aye, sir. I suppose so."

His face broke into a smile. "Well, we had to fatten up your cousin too. Mr. Sharp, please join the line!"

FOUR

The sun was just starting to creep above the tree line when the proper military men arrived. They rolled across the field in an all-terrain carriage drawn by two lupine tigeresques, pulling up smartly before the line of recruits. The beasts' muscles bulged under the leather straps of the carriage rig, and when one shook itself like a monstrous house cat, sweat flew in all directions.

In the corners of her vision Deryn saw the boys around her stiffen. Then the carriage driver set the tigers growling with a snap of his whip, and a nervous murmur traveled down the line.

A man in a flight captain's uniform stood in the open carriage, a riding crop under one arm. "Gentlemen, welcome to Wormwood Scrubs. I trust none of you is frightened by the fabrications of natural philosophy?"

"ADDRESSING THE APPLICANTS."

No one answered. Fabricated beasts were everywhere in London, of course, but nothing so magnificent as these half-wolf tigers, all sinews and claws, a crafty intelligence lurking in their eyes.

Deryn kept her eyes forward, though she was dying to take a closer look at the tigeresques. Before today she'd seen military fabs only in the zoo.