“It is good to be tall, Mademoiselle.” He was still grinning.

“Unfair, you mean.” But she smiled when she said it.

They walked carefully up the gable. Sophia crouched before her dormer window, took a sliver of metal from a small hook under the gutter, and used it to trip her latch. She pushed open both windowpanes, swung her legs through, and hopped inside, René after her. Her room was very dark, and with that slightly stale smell that meant no one had been living inside it for a few days; she hated it when a place that was hers smelled that way. She went to the mantel over the hearth—a formal thing of white marble, glowing ghostly in the starlight from the window—took the tinderbox, and put it in René’s hands.

He accepted it without comment, and she walked across her rugs to the tune of flint on steel. She knelt and pulled a wooden box from beneath the bed. By the time she had brought it to the hearth there was a small fire just kindling, the mantel candles brightening their end of the room. René held one of them up.

“This is your room?”

“Yes.” They were holding their voices low. The quiet seemed to dictate it, even though there were two levels and many layers of hallways and stairs between themselves and Mr. Halflife. She put the box on the hearth rug, settling herself down beside it. René was gazing at everything, turning a half circle with the candle, his hair coming loose from its tie. “What?” she said.

He looked down. “There are little blue flowers. Painted on the walls.”

“Yes,” she said slowly. “Did you forget that I’m a girl? Is it the breeches?”

“No, Mademoiselle, I had not forgotten.” One corner of his mouth lifted. “And that is the fault of the breeches, I think.”

Sophia decided not to ask him what he meant by that. She busied herself with the box, so her hair would hide her telltale flush. “My mother painted the walls, so I don’t want to have them changed. And the curtains are lace, too, by the way. I thought I’d point that out first and save you the astonishment.” When she peeked up, both corners of his mouth were turned up. “Sit with me,” Sophia said, “and I’ll show you what I made you climb a roof for.”

He sat on the opposite side of the box from her, as if suddenly remembering caution, setting the candle on the safer surface of the hearthstone. What had she hoped to accomplish by bringing him up here? What she wanted was to understand him, and this was only going to reveal herself. He pulled up his long legs, waiting.

She brushed the dust from the box—her room was not as immaculate as Spear’s—and opened the lid. Packed inside in soft cloth were pieces of clear glass, square, about the size of a windowpane, leaded together in sets of two. Trapped between the pieces were fragments of paper.

René lifted a pane, holding it near the candlelight. The paper inside the glass was brown, in bits and cracking. “There is writing,” he said. “Printed.” He turned the glass over. “On both sides. How old is this? Did the Bellamys print it?”

“No. It’s much older than that. It’s as old as Bellamy House, we think. My grandfather found them in the walls.”

“They are from Before?” He touched the glass over the paper with a finger, as if he could coax it into speaking. Sophia felt her smile break free at his expression.

“Can you read them?” she asked. “It’s a story.”

He held the glass closer to the light. “St. Just! Is that why …”

She nodded.

“And Marguerite! It was my mother’s mother’s name.”

“The one who was such a liar?”

“No, the other one.” He grinned. “Who was also a liar.”

“There are only bits of the story, but …” Sophia searched through the pieces until she found the one she wanted, scooting around the box to show him. He leaned in to see, caution lost. “This is what I wanted to show you. It says, ‘The dull boom of the gun was heard from out at sea.’ ”

René took the glass in his hands, reading it himself, soft Parisian beneath his breath. “It is real, then,” he said, more to himself than her.

“And look, they call it ‘firing’ the gun.”

“Like Bellamy fire?”

She smiled. “Maybe. I don’t know.”

He gazed at the words. “Does it makes you wonder … what else …”

“What else your grand-mère said that might be true? Like hidden pictures on mirror disks and flying through the air and machines on the moon?”

“Yes,” he said, “just so.” Sophia watched him running reverent fingers over the glass, his hair such an extraordinary color in the candlelight. If he was an actor, he was the best in history.

“This is my favorite.” She pointed at the words. “It says, ‘The walls of Paris,’ and right here, she calls someone ‘Monsieur …’ ” She felt René’s eyes dart up at that. “It’s even spelled the same. And here, she—whoever she is—talks of being condemned to death, and that someone has hidden her children—and herself, I think—beneath some … things in a cart and helped her escape. And the driver is in disguise. He uses tricks to smuggle them out, you see, and he leaves something behind him …” She hunted through the tiny, dim words and pointed.

“What is a ‘pimpernel’?” René asked.

“I’m not sure. Tom thought it might be a flower, or a drawing of one. But I think he uses it like a signature, so no one else will be accused of his crimes, which is rescuing the people from a prison before they can die. No one knows his real name, only the sign of the ‘scarlet pimpernel.’ That’s about all Tom and I could make out, and it took us ages. It’s very hard to read.”

René’s body had gone very still, the little pulse beyond his collar the only movement. The intensity of his gaze on the glass was something she could feel. “And so now,” he said, voice low, “you go to the Sunken City, which was Paris, and you bring the people out of the Tombs before they die. And you leave a rook feather painted red behind you.”

She nodded. He leaned forward, and then all the energy of his gaze was on her.

“Why?” he said. “Tell me why you do it.”

Sophia looked down. Their small fire was already smoldering in the hearth, making the room even darker.

“Come,” he said, almost a whisper. “Tell me.”

Without looking up she said, “Every summer we went to the city to stay with Aunt Francesca, my mother’s aunt. She was Upper City, near the Montmartre Gate, about halfway up,” she explained, referring to the level of the apartment flat, “one of the first women to teach history at the Scholars Hall. And she was busy, and Father absorbed, and Orla never came to the city, because she is afraid of boats. Tom always teases her about that, about her luck being born on an island …” She smiled just a little. “And so Tom, Spear, and I, we ran about like wild things, I guess. We climbed into the Lower City every day it wasn’t raining.” She ran a hand through her tangle of hair. “I loved it there. The rules were different, not so polite, and it was like a whole secret life, something that no one knew about but the three of us. I went with Mémé Annette to Blackpot Market, and Tom and Spear taught Mémé’s son Justin to read, even though he was grown. They felt very important about that. And no one cared that we were Upper City. Maybe because we were young, or Commonwealth, or maybe they’d just gotten used to us. But that last summer before Allemande …” She paused. “That last summer everything changed. Our first day back we scaled the cliff wall. I’d brought grapes from the greenhouses for Mémé …”

She gathered her thoughts, and again the power of his focus was something she could feel on her face.

“Do you remember when the old premier broke the Anti-Technology Pact and lifted the embargo on simple machines, and a mill owner tried to install a waterwheel? How he told the grindstoners he’d sacked that they would be better off without their jobs, because the wheel would lower the price of their bread?”