Mamusia let herself into the room at just past four in the morning, sliding into bed, and Eva finally allowed herself to drift off, comforted by the warmth of her mother’s body.

When Eva awoke a few hours later, the sun was reaching filament fingers into the room along the edges of the blackout curtains. Eva turned to look at her mother, sleeping peacefully beside her, and she felt a surge of sadness. The fight had gone out of Mamusia, and without it, she looked like a little girl. Then again, perhaps in a way she still was. Mamusia had been only eighteen when she married Tatu?. Without her husband beside her, she didn’t know who she was as an adult. Eva dressed in silence and left without waking her.

“Will you look after her today?” she asked Madame Barbier as she passed the older woman in the hall on the way out.

“That depends. Are you going to see Père Clément?”

Eva hesitated and nodded.

“Good. Then I will care for her,” she confirmed. “Wait here for a moment.” When she returned, she was carrying an apple and a wedge of cheese. Eva held up a hand to refuse, but her growling stomach gave her away, and Madame Barbier insisted with a smile. “I will save some for your mother, too. You will both need your strength.”

The streets of Aurignon were quiet as Eva hurried toward the église Saint-Alban a few moments later, clutching the food. But it wasn’t a peaceful silence; the clean air was still, as if the sky was holding its breath, and there was no birdsong. Behind the church, the squat mountains in the distance looked ominous today as they cast their scattered shadows over the town.

Père Clément was sweeping the aisle, and he looked up when Eva entered. “Is your mother all right, Eva? I saw her in the town square last night. You should remind her that it’s dangerous to be out after sundown. It’s a small town, and in small towns, people talk.”

“I’ll tell her. And I think she’s okay.” She hesitated and added, “Just broken, I suppose.”

“We all are.” He smiled at her sadly. “Eva, Rémy brought me the documents last night. The work you did was incredible.”

She ducked her head so he wouldn’t see her blush. “Thank you. Will it help?”

“It already has. I’ve brought you more supplies. And as long as you’re willing to stay, well, we would be very grateful for your assistance.” He handed her a key. “Here. This will let you into the library. Aside from me, you and Rémy are the only ones who have these.”

He walked away before she could reply. She allowed herself a small smile before heading to the tiny library.

When she let herself in, she was surprised to find Rémy already sitting at the table, hunched over something. He looked up with a smile as she pulled the door closed behind her.

“I brought an apple and some cheese if you’d like to share,” she said, pulling the food from the pocket of her skirt and holding it out, a peace offering.

He eyed the small meal. “You don’t need to give me any.”

“I know I don’t,” she said. But she handed him the cheese anyhow and waited until he’d taken a small bite.

“Thank you.” He passed the cheese back and waved away the apple. “As it turns out, I have something for you, too.” He held up the book she’d grabbed in a panic the first night she met him, Epitres et Evangiles, the thick, faded guide to weekly masses from the 1700s.

She frowned as she took the book from him. “Are you poking fun at me?”

He laughed. “No, quite the opposite. Please, turn to page one.”

She looked at him uncertainly. He laughed again and gestured to the book. “Go on.”

Slowly she cracked it open and turned to the first page, which featured only the title of the book, a subtitle, the publisher name, and the year of publication. She gave him a look. “But what…”

“No, no, keep going. Numerical page one.” The old paper crackled in protest as she leafed through the first eighty or so pages, marked with roman numerals, and found numerical page one. There was a tiny black star drawn over the e in Le, followed by a dot over the v in l’Avent on the same line.

Eva looked up in confusion. “You’re defacing old books now?”

Rémy laughed. “For a good cause, I think. Keep going. Page two.”

On the second page was a dot over the a in car, and on the third, a dot over the t in perfécuteurs, but nothing had been added to page four. On page five, there was a dot over the r in alors, but on page six, there were no marks. “I don’t understand,” she said, setting the book down.

“Have you ever heard of the Fibonacci sequence?” Rémy asked.

“I don’t think so.”

“I’ve always loved math. You see, the Fibonacci sequence starts with the number one, then the number one again. Add those numbers together to get two. Then add one and two together to get three. Two and three make five. Three and five make eight. And the series continues like that, adding the two previous numbers to get the following number. Do you understand?”

Eva squinted at him. “I understand the math. But I don’t understand what this has to do with an old book.”

He grinned. “Stay with me, Eva. Now, continue the sequence, if you will.”

“Rémy…”

“Just trust me.”

She sighed, feeling as if she were back in l’école primaire, being given a surprise quiz in mathematics. “Very well. One, one, two, three, five, eight, thirteen, twenty-one, thirty-four…” She trailed off.

Rémy was jotting down the numbers as she said them, then he handed her the paper with the numbers he’d just written. “Now, go to each of those pages and find the dot. Write down on this sheet of paper the letter beneath it.”

Eva frowned, but she did what he said. On page eight, there was a dot over the a in ap?tre. On page thirteen, there was a dot over u in suite.

It wasn’t until the dot over the b in considérable on page twenty-one that she realized what she was writing. “Is this my name?”

“Very good. It’s a way to keep a record of who you are, so that you’re never erased.”

She looked up at him in astonishment. “Rémy…”

“It’s not foolproof, I suppose. But who will be looking in an old Catholic religious book to find the names of missing Jewish children? And who would think to decode the stars and dots this way? It should be easy enough. Each name will begin on a new page, and we’ll simply add that number to each number of the series. For example, the second name will begin on page two, and then on to page three instead of two, page four instead of three, page six instead of five, page nine instead of eight, and so on. If there’s already a dot on the page, well, simply proceed with a new dot, and it will just make the code that much more difficult to decipher if anyone ever tries.”

Eva’s head spun. “But what about the false names we’re giving the children? How will we keep track of those without making the children discoverable?”

“Simple. Just start at the back of each person’s sequence and encode the false names in reverse order. Let’s take you, for example. The book goes to numerical page six hundred eighty-eight, so the last number that would fit in the book from your sequence would be six hundred ten. We’ll start there with a triangle over the first e, then over the v on page three hundred seventy-seven, the a on two hundred thirty-three, and we’ll start your false surname, Moreau, on page one hundred forty-four. So on like that until we have the whole name down, in reverse, on the very same pages we put your real name. If we run out of room in either direction—if there are more letters than there are pages—it’s fine. The beginnings of names should be enough to jog our memories in those cases. You see, Eva? It’s nearly perfect.”

He grinned at her and she felt breathless. She looked back at the book, and then at him. “You just came up with this?”

“I was up all night. You were right, Eva. We can’t erase the children who might not be able to speak for themselves. We’ll keep a list of all of them.”

“I—I don’t know what to say.”

“You could say, ‘Rémy, you’re a genius.’ Or, ‘Rémy, you’re devastatingly handsome.’?”

Eva laughed, surprised to feel tears in her eyes. “Yes, both of those things. And also, Rémy, you’re a hero. This is remarkable. But what if Père Clément is right about the dangers of keeping the list?”

Rémy shrugged. “He is. And that’s why this system will work. I’m sure of it. No one will discover the book, and if they do, the stars, dots, and triangles won’t mean a thing. Besides, we’ll keep it in plain sight on the shelves; who would think to look inside for anything suspicious anyhow?” He paused. “The pages will fill up fast, so we’ll start with black ink, and if we run out of room in the book, we’ll go back to the start and use blue.” He opened the book once again to the first page and pushed it gently toward Eva. “But we’ll never start another name on page one. That will only be for you.” When Eva looked up at him, his expression was somber.

She met his gaze and then glanced down at the book, her cheeks warm. “I don’t know how to thank you for this, Rémy.”