Rosa smiled, her eyes hidden. “No, I don’t miss him. I lost him, or he lost me, too long ago for that.” She touched Lucia’s shoulder. “And anyhow, the Order is my family now. Isn’t that true?”

Lucia was uncertain how to respond. “Of course.” That didn’t need saying. It shouldn’t be said.

“Come on. Let’s go inside.”

Lucia looked back once. The redheaded boy had gone.

The Pantheon enclosed a broad, airy volume. There was an altar, the walls were decorated with paintings and holy figures, and the floor was a cool sheet of marble across which tourists wandered.

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?”