Regina said, “Why doesn’t she get a carriage? She could put her stuff in the back. I certainly wouldn’t like to carry my luggage along the road like that …”

Aetius grimaced. “I doubt if anybody other than Hercules could carry your luggage, child. But I’m afraid she doesn’t have a choice.”

“Because she’s poor.”

“Or a slave. And look, over there.” A group of people, shuffling behind a slow-moving carriage, were bound together by ankle chains. “Carriages and horses are faster, but not everybody can afford a horse.”

She frowned. “Are slaves cheaper than horses?”

“Yes. Slaves are cheaper than horses. Look at the countryside. I bet you’ve never been so far from home before, have you?”

She had no idea if she had or not. She looked around at fields and hedgerows. There were a few buildings scattered here and there, small square huts and a few roundhouses with timber frames and thatched roofs; in the distance she saw the bright red roof tiles of something bigger, probably a villa.

It was farming country. Much of the Roman diocese of Britain was like this. Nobody knew for sure how many people lived in Britain south of the Wall, but there were thought to be at least four million. Only perhaps one in ten of the population lived in the villas and towns. The rest worked the land, where they cultivated wheat, barley, oats, peas, beans, vegetables, and herbs, and raised their cattle, sheep, and goats. Many of them had worked this land for generations, since long before the coming of the Romans: Regina might have been traveling through the landscape of five centuries earlier.

It was this way from end to end of the Empire, across two thousand miles, from Britain to the Middle East. The Empire was the most materially sophisticated civilization the western world had yet seen — but the overwhelming majority of people lived off the land, as they had always done.

Aetius spent a long time trying to explain some of this, but he got stuck on the meaning of the word million. Regina’s attention drifted, distracted by the sway of the horses, the clatter of the wheels, the buzzing of flies.

“Oh, stop fidgeting,” Aetius snapped. “If only I could just order you to sit still …” He pointed with his switch at a little cylindrical pillar set beside the road. “Well, what’s that? Do you know?”

She knew very well. It was a waystone. “It tells you how far it is to the nearest town, and who the Emperor is.”

He grunted. “Somehow I doubt that poor Honorius has gotten around to painting his name on the stones … But, yes, that’s the idea. Now, the stones are set every thousand paces or so along each main road. And if you count them, you’ll know how far we’ve come, won’t you?”

“Yes!” She rubbed her nose. “But what if I fall asleep? Or what if it’s dark?”

“If you fall asleep I’ll count for you. And don’t rub your nose. You have to start now. That’s one…”

“One.” Solemnly she folded a finger back as a marker, and peered along the road for the next pillar. But it seemed an awful long time coming, and by the time she saw it she had forgotten what she was supposed to be doing, and had let her finger fold out again.

Her grandfather seemed determined to keep up her schooling, and as they rattled along he told her the story of the road itself. The soldiers from the army of Emperor Claudius had first come this way, surveying the route. The road had been built by the soldiers themselves, and people drafted in from the countryside.

“How much did they get paid?”

“Paid? Hah! Everybody was a barbarian in those days, child. You didn’t get paid. Look. You put down a gravel core, and lay on a surface of crushed limestone. You use stone slabs where you can find them. The water drains out into those side ditches — can you see? …”

She was good at pretending to listen, while being occupied with her own thoughts. But eventually she drifted asleep, slumped against Aetius’s sturdy form, dreaming fitfully about the little girl in her hobnailed boots.

She dozed through the day, or listened to Aetius’s complicated talk, or played word games with Cartumandua. They stopped only to water and feed the horses; the passengers ate on the move in the cart, bread with fish and meat.

The last time Regina woke up that day, the cart was pulling into a courtyard. As Aetius and the others jumped down and began to unload, Regina stood up on her seat, stretched and massaged a sore rump, and looked around. The light was fading from the sky, and high, thin clouds had gathered. To her right she could see a wall, tall and formidable, a great curtain of slate gray two or three times her height that curved away across the ground.

She pointed. “There’s a town! Is it Durnovaria?”

Aetius snorted. “We’ve come a little farther than that. Haven’t you been counting the waystones? We passed twenty-three — not a bad pace after a slow start. That is Calleva Atrebatum.”

“Aren’t we going to stay there? … What’s this place? Is it a villa?”

It was no villa but one of the mansiones, a way station designed to support the messengers of the Imperial Post. It was here, Aetius said, that they would spend the night, for it was safe enough, and he would “swim to Hades before I give over any more ‘gate tax’ to any more swindling landowners in any more towns.”

The station turned out to be comfortable enough. It even had a small bathhouse, where Aetius retired with a pitcher of wine and a plate of oysters, bought for a price that made him groan out loud.

After a day spent largely sitting on a wooden board, Regina was too full of energy to sleep. And so, after she had eaten, despite the lateness of the hour, she, Macco, and Carta played trigon, a complicated three- person game of catch-the-ball. Regina ran and laughed, burning up her energy, and her voice echoed from the station’s plaster walls. Macco stayed as silent as ever, but his smile was broad.

The next day Aetius was again up and ready to go not long after dawn. It didn’t take long to reload the carriage, and soon the four of them were on the road again — though not before Aetius sniffed the air and inspected the clouds and the trees and the birds, seeking omens for their journey.

They continued to head steadily east. The road ran straight and true, unchanging, the way markers sliding past one by one. But the landscape changed slowly, becoming more hilly, and some of the plowed-up fields gleamed white with chalk.

Some of the villas looked abandoned, though, even burned out. On one farm, close to the road, Regina recognized a vineyard, rows of vines set out on a south-facing hillside. But though the vines were green and heavy they looked untended, and the nearby buildings were broken down. Aetius did not comment on the abandoned vineyard, and Regina thought nothing of it. If she had, she would have said that things must always have been this way. She did want to go see if there were any grapes, but Aetius ignored her pleas.

That night they again stayed in a way station.

And the next morning, soon after the start, when they passed over the crest of a hill, Regina glimpsed Londinium itself. The town was a marvelous gray-green sprawl of buildings contained within a far-flung wall. A shining river ran through it. Smoke rose everywhere, thin threads that spiraled to the sky. Regina thought she saw a ship on the river, a green-sailed boat that sparkled in the low morning sun, but she couldn’t be sure.

“Are we going on a ship?”

“No — child, I told you already. We aren’t stopping in Londinium. We’re going on. Don’t you listen?” Aetius seemed to be getting angry. But Carta put her hand on Regina’s shoulder, and he subsided.