But it was the roof that drew Lucia’s gaze. It was a dome, decorated with a cool geometric design, quite unlike the clutter on the walls. The structure seemed to float above her. The only illumination in this immense space came from a hole in the domed ceiling, the oculus. The light it cast showed as a broad beam in the dusty air, and splashed a distorted circle on one wall.

Rosa murmured, “The dome is bigger than that of Saint Peter’s in the Vatican. Did you know that? But the building was started before the birth of Christ. The Pantheon was built as a temple to all the pagan gods, but was turned into a Christian church in the seventh century, which saved it from being torn down. Now it’s the most complete of the buildings of antiquity left. Of course it has suffered even so. Once the dome was clad, inside and out, by bronze, but that was stripped away by the Barberini popes to make cannons. What the barbarians didn’t do, the Barberini did, as they say.”

Lucia gazed up at the disc of blue sky. “We used to get taken to the Forum area all the time, as kids. But you get used to the imperial-era stuff as just a heap of ruins. You forget that it was once all intact — that it was once all like this.”

“Yes.” In the subdued light of the Pantheon, Rosa had taken her dark glasses off, to reveal slate-gray eyes, just like Lucia’s own.

Lucia said, “I think you should tell me why you brought me here.”

“All right. Look at this building, Lucia. It was rebuilt by the Emperor Hadrian, but the Renaissance artist Raphael is buried here, as are the first kings of Italy. The same building, you see, serving many purposes over time. But at root it is the same Pantheon, the same expression of its architect’s vision.”

“I don’t understand.”

Rosa laughed. “I’m starting to think I’m becoming heavy-handed in my old age. I’m being metaphorical, Lucia.”

“Oh.” Lucia made a stab in the dark. “The Pantheon is like the Order?”

“Well, yes, I suppose so, though that isn’t what I meant. After all, this church is even older than the Order itself. Yes, the Order has survived for sixteen centuries by adapting, by changing what we do to suit the needs and pressures of the times. But we, who we are and why we gather together, that at heart hasn’t changed.

“And just as the Pantheon has survived, though it changes — just as the Order survives, though it changes — so you, too, will survive the changes your body is taking you through, now and in the future. That’s what I wanted to show you. Why, if you hadn’t grown up in the Order your menarche would seem normal for a girl your age. Whatever becomes of you — whatever is asked of you — you will still be yourself. Remember that.”

Whatever is asked of you: now Lucia felt scared.

Rosa raised her face to the great halo of light in the ceiling. “You should take some time for yourself, Lucia. Come out again — immerse yourself in Rome. One of the most remarkable cities in the world is on our doorstep, and yet down in the Crypt we often behave as if it doesn’t exist! And I don’t mean with your classes. Come by yourself — or with a friend or two, if you like. That girl Pina seems sensible. Immerse yourself in humanity for a while.”

It will prepare me, Lucia thought. That’s what she’s telling me. I must broaden my experience, to prepare for — what?

“You’re talking in riddles, Rosa,” she flared. “What is to be asked of me?”

“A great deal, if you are lucky. You’ll see. I’ll do what I can for you — but always remember, I envy you! It isn’t duty, but privilege.” Rosa glanced at her watch. “Now we must go back. There’s somebody I want you to meet.”

“Who?”

“Maria Ludovica.”

Lucia felt as if her heart had stopped, there in the dusty air of the Pantheon. Ludovica was one of the matres.

Rosa smiled, watching her reaction.

The elevator was steel-walled, and it slid into the ground smoothly, all but silently. All very modern, as was much of the equipment in the Crypt. Rosa stood in patient silence watching the elevator’s LED display, hands calmly folded before her. Lucia envied her composure.

Lucia vaguely imagined the Crypt as a great drum shape, sunk deep into the ground beneath the old Appian Way. There were at least three levels — everybody knew that much. On the first story, nearest the surface, there were schools, offices, libraries, and the computer center where she herself worked on the scrinium ’s endless projects. On the story beneath that — downbelow, as the Crypt jargon had it — there were living accommodations, the dormitories and rest rooms and dining rooms, food stores, kitchens, a hospital, all of them crammed, day and night, with people. Few of the day girls who attended the Order’s famous schools would ever descend this far, and the light shafts didn’t reach; there was only the pale glow of electric lights, and in the old days, it was said, candles and torches.

And there was at least one more level downbelow.

The elevator whispered to a halt. The doors slid open to a mundane white-walled corridor: the third story. Rosa led the way out with a reassuring smile. Lucia followed reluctantly. The corridor was narrow. Some of the doors leading off the corridor were heavy, as if designed to keep an airtight seal. There was a faint smell of antiseptic here, heavily overlaid with a more pleasant scent, like lavender.

Lucia’s heart pounded. She didn’t know anybody who had visited the third level. Lucia herself hadn’t, not since she was a very small child. From what little she knew, this was a place of nurseries and crиches. She herself had been born here, and had spent her first couple of years here. She remembered nothing but a blur of smiling faces, of pale gray eyes, all alike, none special, all loving.

And, so went the whispers in the dark, this was a place of mortuaries. You were born downbelow, here on the third story, and you died downbelow. So it was said. Lucia didn’t want to know.

The corridor was crowded, of course. In the Crypt, everywhere was crowded. People smiled, nodded, and ducked out of the way as Rosa forged ahead. Almost everybody was female. Most people wore everyday clothing, but some wore simple cotton smocks that looked like nurses’ uniforms. Though most shared the usual lozenge-shaped features and smoky gray eyes — and even though everybody seemed young, not much older than she was — there wasn’t a single face here that Lucia recognized.

Lucia had heard bits of dormitory gossip that the Crypt might hold as many as ten thousand people in its great halls and corridors. That scarcely seemed credible — but then, wherever you looked, there were always more corridors, more chambers, stretching on into the electric-lit dimness: who was to say how far it stretched? She would never know, for she would never need to know. Ignorance is strength …

And it was possible, she thought now, that nobody knew the whole picture — nobody at all.

Here on the third level people stared at her openly. Their manner wasn’t hostile — some of them even smiled at her — but Lucia felt herself cringe. This wasn’t her place; they knew it, and she knew it. The pressure of those accusing glares made her long to flee back to where she belonged. She felt breathless, almost panicking, as if the air in these deep chambers were foul.

If only she could be like Rosa, who seemed to be accustomed to flitting between the stories with the ease of a dust mote in the Pantheon.

At last Rosa paused by a door. Lucia felt a vast relief. Whatever lay ahead, at least she was done with the ordeal of the corridor. Rosa opened the door, and let Lucia go through first.