"Lina couldn't sleep at first, thinking of the old songs and what they meant. Someone, long ago, had hoped that at least a few people would survive and had wanted them to remember her city and the treasure it held, the treasure that was most valuable of all - herself, her family, and all of the generations of people who had lived in that secret place, their purpose, though they didn't know it, to make sure that human beings did not vanish from the world, no matter what happened above."