The sky was smoggy that night, and glowed faintly gray-orange. There was plenty of light from the lamps that played on the monuments in the Forum and on the great gaudy Vittoriano. We were cupped by the great shoulders of Trajan’s Market, which loomed all around us.

I had taken a couple of walks around Trajan’s Market, which I found astonishing. You couldn’t say the ruins were attractive: the market was just a mound of brickwork, of streets and broken-open domes and little doorways. But it had been a shopping mall, for God’s sake. The little units — all neatly numbered and set on multiple levels along colonnaded passageways, or in great curving facades that would have graced the Georgians — had been planned and leased out, just like a modern development.

“That’s what strikes you,” I said to Peter. “There’s nothing medieval about this area — not like the center of British cities. Everything is planned, laid out in neat curves and straight lines. The Forum looks antique, if you know what I mean. Columns and temples, very ancient Greek. But the big palaces look like the ruins of the White House. And this market looks like the ruins of Milton Keynes.”

“Except Milton Keynes won’t last so well as Roman brickwork. They didn’t have slaves to mix the concrete so well.”

“You know, in the Dark Ages they used this place as a fortress. From shopping mall to barricade.”

He nodded thoughtfully. “Decline and fall, eh? But there were a few junctions in Rome’s history where things might have turned out different.”

“Such as?”

“Such as the loss of Britain. Needn’t have happened. Britain wasn’t just some kind of border outpost. Britain was protected by the ocean — mostly anyhow — from the pressures of the barbarians, and internally it was mostly at peace. For centuries it was a key source of wheat and weapons for the troops in Gaul and Germany, and it had a reserve of troops that could have been used to reverse the setbacks in western Europe. Even after the calamities of the early fifth century — if the emperors had won Britain back, they might have stabilized the whole of the western Empire. Maybe your grannie understood some of this.”

“If she ever existed.”

“If she existed. Well, she was the daughter of a citizen, the granddaughter of a soldier. If you’re living in great times, decisive times, you know about it, even if you only glimpse a small part of it.”

“Do you think this story of Regina can be true?”

“Well, I read the book. It’s plausible. The place-names are authentic. Durnovaria is modern Dorchester, Verulamium Saint Albans, Eburacum York. Some of the detail makes sense, too. The old Celtic festival of Samhain eventually mutated into Halloween … Trouble is, nobody really knows much about how Roman Britain fell apart anyhow. For sure it wasn’t like the continent, where the barbarian warlords tried to keep up the old imperial structures, though with themselves on the top. In Britain we got the Saxons — it was an apocalypse, like living through a nuclear war. The history and archaeology are scratchy, ironically, precisely because of that.”

I nodded, and sipped a little more limoncello. The bottle was already getting low. “And if the Empire had survived—”

He shrugged. “Rome would have had to fight off the expansion of Islam in the seventh century, and the Mongols in the thirteenth. But its armies would have handled the Golden Horde better than its medieval successors. It could have endured. Its eastern half did.”

“No Dark Ages—”

“The one thing you get with an empire is stability. A solemn calm. Instead of which we got a noisy clash of infant nations.”

“No feudalism,” I said. “No barons. No chivalry. And no English language. We’d all have ended up speaking some descendant of Latin, like French, Spanish—”

“No Renaissance. There would have been no need for it. But there would have been none of the famous Anglo-Saxon tradition of individual liberty and self-determination. No Magna Carta, no parliaments. If the Romans had gone to the Americas they wouldn’t have practiced genocide against the natives, as we did. That wasn’t the Roman way. They’d have assimilated, acculturated, built their aqueducts and bathhouses and roads, the apparatus of their civilizing system. The indigenous nations, in North and South America, would have survived as new Roman provinces. It would have been a richer world, maybe more advanced in some ways.”

“But no Declaration of Independence. And no abolition of slavery, either.”

There would have been losses, then. But the fall of Rome — all that bloodshed, the loss of learning — the collapse of order: no, I realized, I didn’t think that was a good thing. The order of empires appealed to me — even if, for example, the Soviet Union had been just such an empire by any reasonable definition. But that was my inner longing for order and regularity expressing itself.

We sat for a while, listening to the cicadas chirp in the trees, whose green leaves looked black as oil in the smoggy orange light. One of the other drunks was watching us; he raised his brown paper bag in ironic salute, and we toasted him back.

“So. My sister,” I said. “What do you think of her ?”

He shrugged. “Sounds inhuman. I don’t know how you ought to behave when your long-lost brother turns up out of the blue, but surely it’s not like that.”

I nodded. “What do you think we’re dealing with?”

“A cult. A creepy fringe-Catholic cult. I think your sister has been indoctrinated. No wonder she reacted like a robot.”

I forced a smile. “If you’re thinking of deprogramming her, forget it. She says she doesn’t need saving.”

“Well, she would say that.” More gently he said, “And after forty years, and after being taken at such a young age, there’s probably very little left of your sister anyhow.” He sighed. “Your dad was a good friend of mine. But he had a lot to answer for.”

“What about the Order?”

“You know, Jesus Himself never meant to found a church. As far as He was concerned, He was living in the end times. He had come to proclaim the kingdom of God. The early church was scattered, chaotic, splintered; it was a suppressed movement, after all.”

“And women—”

“When the persecutions began, women had it particularly tough. Women martyrs were made available for prostitution. Women would need a place to hide, a way to gather strength, to endure …”

“So the story of the Order makes sense.”

“Once it became the religion of the Empire, the church quickly tightened up. Heresy wasn’t to be tolerated: for the first time you had Christians cheerfully persecuting other Christians. In the centuries that followed, as the popes got a grip, the church became centralized, legalized, politicized, militarized. The Order would have had no place in the worldview of the popes.”

“Yet it survived.”

He rubbed his chin. “The Order is obviously secretive, but it’s been sitting there an awfully long time, an hour’s walk from the Vatican itself. The church has to know about it. There have to be some kind of links.” He smiled. “I told you I always wanted to go have a root around in the Vatican’s Secret Archives.

Maybe now’s the time.”

I said dubiously, “I’ll have to ask Claudio.”

I wasn’t happy with his response. On some level he might be right. But he hadn’t taken on board what I’d tried to tell him about what I thought of as the earthy aspects of the Crypt: the faces, the smells, that deep pull I felt to remain there, to go back. Or maybe I hadn’t wanted to expose all this spooky biological stuff to him.

Anyhow, though I couldn’t shape the thought, I was sure there was more to the Order than just a cult. But maybe Peter was going to have to see it for himself.

As if on cue, an opportunity to do just that offered itself.