The professor did his best to continue with his life’s work, published in several groundbreaking papers in France and Germany, coauthored with several renowned German mathematicians who were working on Fermat’s last theorem, proposed by Pierre Fermat in 1637, the most famous but not yet proven theorem in number theory. But now his wife had come to his study to tell him two strangers claiming to be cousins had arrived, interrupting his thoughts about the length of the solar system. It often seemed that his wife, Claire, was speaking an entirely different language, one in which household details played a great part. There was so little food to be had that she had begun a vegetable patch in the garden, tearing out the bellflowers and vivid pink roses in order to plant leeks and cabbages and escarole. She let the rest of it go to seed, and the wilder sections of the garden near the old and beautiful greenhouse, where jasmine and all manner of exotic plants once grew, had become home to glis glis, large dormice that were usually only to be found in the countryside. Madame was practical at all times. She had come to prefer a scraggly plant laden with tomatoes to a fragrant peony, and a mouse to a rat. But cousins were another matter entirely.

“They can’t stay here,” Madame Lévi told her husband. “We’ll be the ones to pay if they’re caught.”

Foreign Jews had begun to be arrested, and now the cousins had come from Berlin, presumably with falsified identity papers. You could tell they were refugees with one look: the battered suitcase, the exhaustion in the girl’s eyes and her short, ragged haircut, the set of the young woman’s mouth, as if nothing they said or did could make her go. Madame Lévi had always managed the household despite the circumstance, but cousins appearing out of the blue, like beggars at their door, was too much. The young woman was especially strange. Although she spoke flawless French, she possessed a shifty look, taking in every detail with her pale gray eyes. She wore a plain dress and heavy boots fit more for a man than a woman, a style that was definitely not French. It was impossible to gauge what her emotions were, let alone her intent. The girl was well mannered, but something was off there, too. She first called herself Lea, then stammered and asked to be called Lillie, as if confused by her own name. Were they thieves or impostors? Was their plan to steal what little the Lévis had left? The professor’s wife resolved to have her husband’s help in the matter despite her vow never to interrupt him while he worked.

“When I asked them to leave they refused,” Claire complained. “They sat down in the hallway and there they are!”