BULGARIA MIGHT HAVE BEEN beautiful. It might have been vast, wild, and green, or drab, treeless, and gray. Stefan did not notice. He concentrated on putting one foot in front of the other, his cousin’s bag slung across his back, his own bag swinging from his shoulder.

Samir carried the black cases along with his own luggage. The Arab hid his grief behind a wall of calm. Stefan had no such defenses.

They had left the river men to their work dismantling the Gray Goose, which was to be sold for her wood. The current of the Danube did not allow for a return trip. The captain and his crew would travel overland back to Germany, where they would build another barge and set sail again.

Stefan and Samir now followed a narrow road that wound its way through a scant forest. Stefan watched the ground, his boots taking one dusty step and then another. The rhythm was steady, plodding. It helped him stop thinking for a while. About his cousin, and the river, and his last glimpse of Christian’s face.

His father standing by his mother’s coffin in the rain. The empty toy shop, ransacked by man or mouse.

His coat was too warm, his feet sore, his legs weak from their days on the river. Still he walked, and the shade of the trees gave way to dappled sunlight. He could feel it on his neck, but he would not look up. Because then he would have to face the future. One in which he was alone.

When they were through the trees, Samir stopped and put the two cases on the mossy ground. Stefan dropped his bags and stretched. Walking might be peaceful, but it was impractical if they were to have any chance of saving his father.

“What are we going to do, Samir?”

The astrologer sat down on the grass and folded his legs in front of him. “I am ashamed to say I do not know. For too long, I’ve been led by the beard, following Christian, searching for the nut. It is as if I am looking up and seeing where I am for the first time.” He gazed out at the peaceful countryside, empty but for the hum of insects and the sigh of the wind in the trees. “I am at a loss.”

Stefan sat down beside the Arab and lay back on the grass. His head hurt. He tried not to think.

“There was a plan,” Samir said at last. “We will follow the plan. Go to Boldavia, bring the nut to the king.”

“But we can’t open it,” Stefan sighed.

“King Pirliwig has a kingdom of men, as you said. Men who might succeed where we have failed. We will trade it for help finding your father, and get you home to Nuremberg. That is what your cousin wanted. I promise to see it through to the end.”

“Promises,” Stefan repeated, remembering. “Just before . . . before Christian . . .” He swallowed and began again. “He told me to remember my promise and he said he would keep his.”

“What did you promise him?” Samir asked.

Stefan sat up. “I don’t know. Nothing that I can remember. He said I looked like my mother, and she’d be proud of me. It was strange.”

“Anything else?” Samir asked intently, as if there were clues in the memory.

“Nothing. He said it was a beautiful day.” He collapsed back to the ground and sighed. “Christian was the master clockmaker. He was the one with the plan. I’m just . . . a toymaker’s apprentice.” Without a master, he could no longer be a journeyman. He’d been orphaned yet again.

“And I am no longer a jailer,” Samir said. “So, what can an astrologer and a toymaker’s apprentice do?”

Stefan recalled the blueprints of the City Clock, layer upon layer. Even the smallest cog fit somehow to make the whole mechanism work. When one cog was removed, another took its place. But he was too young to fill the gap his cousin had left behind.

“‘Promise me you won’t quit,’” Stefan whispered. There was something else Christian had said days ago, after their argument about cracking the nut.

“What’s that?” Samir asked.

Stefan sat up and dusted himself off. “Did you know that too many clockmakers can spoil a clock?”

“What nonsense is that?” The Arab’s patience had worn thin. He rose and began fiddling with his bags.

“It’s true. Christian told me. Once a clockmaker has begun work, only he can finish it. Another hand might throw off the rhythm.”

“What’s that to do with us?” Samir demanded.

“Don’t you see? Christian was my master, but he’s gone. The work is unfinished. Unless I finish it for him.”

Samir stopped his fiddling and gave Stefan a confused look.

Stefan rose to his feet. “Christian said he knew of someone who’d eaten a krakatook. Who was he?”

A vague look crossed Samir’s face. “Allah be praised. He must have meant the Pater.”

“We have to go see him. He’s our only hope.”

Samir shook his head. “Not in this instance, I am sorry to say. The Pater is a squirrel.”

“A squirrel.”

“A wise squirrel. But the krakatook is a religion to such creatures. Like your Holy Grail. If he knew we had it . . . No, we must find some other way.”

“There is no other way!” Stefan cried. “We have to go to the squirrels.”

“Did you not hear me? They will take the nut from you.”

“They’ll try. But I won’t let them—” Like a lens throwing everything into focus, the wheels of his brain were starting to turn, making his path clear. “If the mice succeed and spread out into the world, men will rise up to stop them. Then where will the squirrels be? Hunted alongside the mice, maybe, or driven to starvation by their excess. Professor Blume said the krakatook imparts longevity and wisdom. If there is a squirrel who has eaten one, he’ll see I’m right. He’ll be sensible where kings and queens might not. Please take me to the squirrels. For my father’s sake.”

Samir regarded him for a long moment. He reached for the satchel that held his telescope and star charts. He spread the charts on the grass, weighing the corners down with rocks, and read the strange series of circles and lines.

“How can star charts possibly—?”

The Arab held up a finger for silence. Stefan paced impatiently, but Samir paid him no heed. Instead, he muttered under his breath, pulled out a small instrument, and made some measurements. Using a tiny pencil, he jotted a few notes, nodded, and stared at the result.

Stefan stared too, clueless.

At last, the astrologer slowly rolled up his charts. He carefully packed away his instruments and closed his bag. “All right.”

Stefan scrambled to his feet. “All right? You’ll take me there?”

Samir shrugged. “Yes. It seems I am fated to travel with one Drosselmeyer or another. I cannot argue with the stars.”

Stefan took a deep breath, filling himself with purpose. “Right. Then we’ll have to get horses,” he said. “I don’t see us carrying all of this for more than a mile or two.”

Samir knelt beside his case. “Well, these are yours now. It’s time you learned how to use them.”

He opened the first case. It collapsed into two neat rectangles. “Help me with the legs,” the astrologer said.

Stefan stared at the box. “Legs? We’ve been carrying around picnic tables?”

“Not that kind of leg,” Samir said, and unfolded a section of the box. It was sleek, black, and curved, and ended in a hoof.

“What the devil is that?” Stefan asked.

Samir scowled. “Pay attention. Legs!”

He bent to the task of unfolding two more legs while Stefan, a bit belatedly, addressed the fourth.

“There. Now help me turn her over.” Squatting to get their fingers beneath the rest of the box, they gently rotated the whole affair so that it sat on top of the hooves, looking for all the world like a tall, unattractive desk.

“Oh.” The puzzle clicked into place. Stefan shook his head in admiration. “Very clever.”

“‘Magnificent’ was the word I used when I first saw them,” Samir said. He helped Stefan open the second box. When both “tables” were set up, Samir pulled a winding key from along the inside of the box, adorned with a long plume of horsehair.

“If you would?” He indicated Stefan do the same. Stefan hurried to the end of the second box and found his own plumed key. “Insert here and twist like so . . .” Samir demonstrated.

Stefan pushed the key into a waiting slot and gave it a twist. The crank of gears increasing in tension greeted him and he grinned. It was like his little wind-up bird, on a much grander scale.

The “tabletops” accordioned upward, like a bellows filling with air.

“Now counterclockwise,” Samir said. Stefan followed along, twisting the key three times in the opposite direction. “Now, step back.”

Stefan did as he was told.

The cases bloomed into horses. The tails, for that is what the keys resembled, unwound slowly and a series of hydraulics and hidden gears lifted each box, plumping it up into the shape of a body. A head cleverly unfolded from the front of each case and flipped itself forward onto a neck that extended to the correct length and height. The mane fell over the neck in a cascade of black. The horses appeared to breathe as the bellows that opened them filled out the lines creased into their sides from storage. Each animal snorted a fine puff of dust and stamped experimentally on four metal hooves before coming to a rest.

Two black stallions, as real to the eye as any horse, stood before him. Their unnatural stillness was the only sign that they were not real.

“Incredible,” Stefan said. He circled the horses. “And they run on . . . steam?”

“Perpetual motion and winding. Christian can . . .” Samir faltered and cleared his throat. “Could have . . . explained it to you better than I.”

Stefan’s eyes stung as he blinked away sudden tears. “Well, I’ll have to teach myself. I hope I do as well with my own inventions someday.”

He secured his bags across the back of the nearest horse and mounted. He smiled as the stallion gave slightly beneath his weight. It was soft but firm, like sitting on a cushion of air.

Samir beamed back. “You did not think we could ride the world for seven years without some comforts, after all?”

Small comforts were all they had left.

Stefan settled gratefully into the saddle and experimentally kicked his heels. The horse responded as naturally as a real one might, striding forward at his touch. The beast was guided by slight pressures on the reins and withers.

Samir assured him they could go at greater speeds than the best horses, as long as their gears were maintained.

“In that case, lead on, with all speed.” Another click of his heels, and they were on their way, to seek fortune or ruin among the squirrels.