"And that's why you want to bring it along tonight?" Alek asked. "In case we need to send semaphore signals?"

Deryn rolled her eyes. "No, you daft bum-rag. It's because ..."

She sighed, unsure exactly how to say it. The loris had a knack for noticing important details, just as Dr. Barlow had claimed. And tonight was the most important mission that Deryn had ever been a part of. She didn't dare leave the beastie behind.

"Perspicacious," the creature said.

"Aye, that's the word," Deryn cried. "Because it's barking perspicacious."

Two weeks before, Zaven had put his posh education to use and explained the loris's species name to Deryn. It turned out that "perspicacious" meant the same as "shrewd," or even "farsighted." And though that didn't sound like the sort of thing a beastie could be, it certainly fit.

Alek sighed, and turned toward the family's apartments, where Nene's tortoise bed was emerging, covered with maps fluttering in the breeze. The old woman called to Lilit and Alek.

As they walked away, Alek said over his shoulder, "All right, Dylan. But I have a walker to pilot. So you'll be looking after it."

"More than happy to," Deryn said softly, scratching the loris's wee head.

Only having the beastie about had made it bearable, working with Clankers and their lifeless machines, smelling of exhaust and engine grease. The bustling splendor of Istanbul was still so alien, its foreign tongues too many to learn in a lifetime, much less a month. Deryn spent her days printing newspapers she couldn't read, and wondering what the prayers gliding over the rooftops might mean. The intricate geometries of Zaven's carpets and tiled ceilings dazzled her eyes, and even the wondrous food often proved to be - like the rest of the capital - too sumptuous.

But hardest of all was being so close to Alek, while still hiding from him. He'd shared his last secret with her, and Deryn realized now that she could have told him that same night, in that dark hotel room with no one about to hear.

But every time she'd tried, Deryn had imagined the look of horror on his face. Not that she was a girl in boy's clothes, or that she'd lied to him for so long. All that yackum Alek would soon get past, she knew. And then he would love her, she knew.

But that was the problem, because there was one thing that would never change.... Deryn was a commoner. She was a thousand times more common than Alek's mother, who'd been born a countess, or even Lilit, an anarchist who spoke six languages and always knew which fork to use. Deryn Sharp was as common as barking dirt, and the only reason that didn't matter to His Serene Highness, Aleksandar of Hohenberg, was that she was also, in his mind, a boy.

The moment she could be anything more than a friend, she would be, and then he'd have to run a mile.

The pope did not write letters to transform orphan daughters of balloonists, or girls in boy's britches, or unrepentant Darwinists, into royalty. She was dead certain of that.

Deryn watched Alek kneel by Nene's bed like a good grandson, the three of them going over the details of the attack one last time. This battle tonight was something they had helped make together, she and Alek, and this was the closest they would ever be.

"A, B, C ... ?" Bovril asked, and Deryn nodded.

She prayed that her signal practice really would come in handy. If all went well tonight, the Leviathan's crew would be taking a long hard look at the Tesla cannon after it had been destroyed. That could be her only chance to let them know that she was alive.

It might even be a chance to go home, and leave her prince behind at last.

The great outer gates of the courtyard swung slowly open, revealing a clear and moonless sky.

"Lucky it didn't rain tonight," Alek said, checking the controls.

"Right enough," Deryn answered. A midnight downpour would have turned the spice bombs into a useless, soupy mess, ruining the Committee's only weapons. That was the thing about battles, Mr. Rigby always said, one squick of bad luck could make all your plans go pear-shaped.

Much like the rest of life, she supposed.

The courtyard filled with the rumble of engines from four walkers. Şahmeran, with Zaven at its controls, raised a giant hand and waved them forward as it slithered out the gates.

Lilit went next, piloting a Minotaur. The half bull, half man bowed low to get its horns through, giant hands out for balance. Spice bombs rattled in the magazine that Master Klopp had welded to its forearm.

Alek placed his feet on the djinn's pedals. Klopp had insisted that Alek pilot an Arab machine tonight; their steam cannon made them the safest of the Committee's walkers. Behind the djinn, Klopp and Bauer sat at the controls of an iron golem.

"Hold on tight, Bovril," Deryn said, and the beastie scampered up onto her shoulder. Its claws poked through her piloting jacket like wee needles.

Alek worked his feet, and the contraption took a huge step forward.

Deryn grasped the sides of her commander's chair, queasy as always in the lumbering machine. At least the djinn was still in parade mode, the top of its head split open, so she could see the stars and breathe fresh air.

"Turn left here," she said. To keep this mission as secret as possible, the four walkers had no copilots. So Deryn was serving as Alek's navigator and, once the shooting started, as range finder for the throwing arm. Deryn had never been a gunner before, but altitude practice had made her a dab hand at estimating distances - as long as she remembered to think in meters instead of yards.

Deryn looked at her map again. It showed four separate routes to the Tesla cannon, with Alek's marked in red. These four walkers were headed out before the main attack began, so they couldn't afford to raise suspicions by traveling together. The trick would be arriving at their target all at the same time.

Also marked on the map were the positions of the other forty-odd walkers pledged to the Committee, poised to spring into action an hour later. Deryn wondered if there were any spies among those crews, ready to sell the Committee's plans to the sultan for a lump of gold.

At least she could be certain that this attack on the Tesla cannon had been kept secret. Zaven himself had heard about it only this afternoon. He'd fumed a bit about being kept in the dark, until realizing that he wouldn't have to face the big guns of the Goeben.

Unless the Admiralty had changed the night of the behemoth's arrival, of course.

"Have you thought about how many things can go wrong?" Deryn said. "It's like the bard says, 'The best laid plans of mice and men.'"

"Fah!" said Bovril, imitating Zaven's tone.

"You see?" Alek said. "Your perspicacious friend is confident."

Deryn looked at the beastie. "I just hope it's right."

They made good time on the almost empty streets of Istanbul. The Committee's walkers had been practicing night walking for the last month, pretending to patrol for robbers, so no one gave the djinn a second glance.

The buildings thinned out at the city's edge, and soon the djinn was traveling down a dusty carriage road. The route was barely wide enough for the walker, and the skirt of steam cannon thrashed the tree branches on either side. When they passed a darkened inn at a crossroads, Deryn saw curious faces peering from the windows. Sooner or later someone would wonder what a walker from Istanbul's ghettos was doing in the countryside.

But they were too close to their target for that to matter now. The landscape climbed, growing rockier as the cliffs rose. The city came into view out the walker's rear viewport, its glitter and brilliance garish in the moonless night.

A hundred masts and smokestacks were scattered across the water's black expanse, and Deryn wondered again what would happen if the Leviathan were shot down. Would the behemoth simply swim away, or go mad among all those unarmed ships?

She shook her head. They couldn't fail tonight.

They were only a few miles from the Tesla cannon when a spotlight lanced out of the dark.

Deryn squinted - her eyes caught a flash of steel, and the silhouette of a trunk and tail.

It was one of the sultan's war elephants, blocking their path.

"Range?" Alek asked calmly.

"About a thousand yards. That is, nine hundred meters."

Alek nodded, pulling a lever. A spice bomb rolled from the magazine into the djinn's hand. Deryn caught a whiff of it and winced. Even wrapped in oiled burlap, the bombs let off eye-burning dust every time they moved.

"Top down, please," Alek said.

"Aye, your princeliness." Deryn set to work on the hand crank, and the djinn's forehead rolled slowly closed across the stars.

Alek stoked the engines, sending power to the steam boilers. The machine's right arm drew slowly back.

Someone in the war elephant shouted at them through a megaphone. Deryn didn't recognize any of the Turkish words, but it sounded more curious than angry. As far as the Ottomans knew, the djinn was unarmed.

"They're just wondering what in blazes we're doing here," Deryn muttered. "No reason to be nervous."

"Nervous," said the beastie.

Alek laughed. "Perspicacious or not, the creature knows you."

Deryn frowned at the loris. Of course she was a wee bit jittery. Only a fool wouldn't be, heading into battle. Especially on a finicky Clanker contraption.

"Loaded and ready to fire," Alek said.

"Hold on." Deryn watched the ranging gauge that Klopp had installed, its needle slowly climbing as steam pressure built in the djinn's shoulder joint.

The tricky bit was, Klopp hadn't been able to test every throwing arm in the Committee's army, so he'd marked the gauges using only math and guesswork. Until their first shot landed, there was no telling how far the bombs would actually travel.

The needle finally reached nine hundred meters....

"Fire!" Deryn cried.

Alek pulled the release trigger, and the djinn's giant hand swung overhead. Clouds of steam gushed from its metal shoulder, turning the air in the cabin scalding.

The spice bomb struck fifty yards in front of the elephant, exploding into a cloud of dust that swirled as red as blood in the spotlight.

"Master Klopp knows his sums," Deryn said with a smile. "Next time we'll hit the bum-rags dead-on!"

"More steam," Alek ordered. "I'm loading another."

Deryn pulled the stokers, and the engines roared beneath them, but the ranging needle was slow to climb. The djinn had exhausted every squick of shoulder pressure with its first throw.

"Come on!" she urged it. "They'll be shooting back any second."

"If this were a proper walker, we'd be taking evasive action," Alek muttered. "What I wouldn't give for a decent gun sight."

"Or a decent gun!"

"These spice bombs were your idea, I seem to - "

The elephant's main turret roared to life, sending a shell screaming overhead. The explosion came seconds later, rocking the djinn on its feet.

"They overshot us!" Alek cried. "But they have our range now. Can I fire yet?"

"Hold on!" Deryn watched the needle climb. The loris dug its claws deep into her shoulder, imitating the whistle and boom of the near miss.

The needle passed nine hundred meters, but she needed another fifty at least....

"Fire!" she finally cried.

The great arm swung again, rocking the cabin backward. The moment the bomb had flown, Alek grabbed the controls and took them charging ahead.

Through the rocking viewport Deryn watched the war elephant disappear into a roiling cloud of red dust.

"Bull's-eye!" she cried.

But the walker's crew still managed to fire - the main gun blazed again, setting the dust cloud around the elephant into a massive whirlwind. The air cracked once more as the shot zoomed past.

The djinn reeled from the blast - the shell had landed right where they'd been standing, Deryn reckoned. Alek struggled with the controls as the walker staggered forward.