Shrinking back in her seat, Leora stared at the book in front of her as if it were growing uncontrollably, the folio widening and thickening until she could imagine all the listings within it—the boyfriends she hadn’t married, the jobs she hadn’t taken, the acquaintances she had abandoned, the endless roster of people she hadn’t become. And then, beyond that, stood the listings of all the people everyone else hadn’t become, all the endless numbers of people who could have been, but weren’t. She felt her hand being drawn back toward the book’s cover, her fingers edging up over the waterlogged table toward the outdated green leather binding. Then she slammed her hands down and stood up from her seat.

“Yes, thank you for your help,” she called to the clerk, her voice self-consciously loud. And she ran out of the room before he had a chance to respond.

WHEN LEORA left the lost city hall, she began to look more closely at the people around her—the people in the streets, yes, but also the people in the windows, some of which were covered with thick curtains, but others of which were glass laid bare, allowing full view of the people behind them. As she looked closer, though, remembering those giant ledgers, she suddenly realized what she was looking at. The people behind the windows, the people in the street, absolutely everyone she had seen in the lost city—they were living through all the things that hadn’t happened in the city above, all the choices that hadn’t been made, all the lives abandoned, to be lived out only on the forgotten ocean floor. There wasn’t only one Naomi in the lost city, Leora realized, but thousands, each a different version of the person she never became. Somewhere in this city, she imagined, she and Jake were married to other people; somewhere else, Wilhelm Landsmann, an old, distinguished gentleman of a modern Vienna, might be in town on a pleasure trip in his retirement. Or perhaps none of them had ever been born, their parents having decided to marry others, or their grandparents having so decided, or their great-grandparents. Among the endless thousands of millions of people who inhabited the lost city, all of these possibilities existed—except for the ones the people above had chosen.

Suddenly she felt, with full force, the immense weight of the millions of gallons of water and abandoned lives on top of her. She fought hard to stay standing, then fell to her knees. The crowds in the street began trampling her underfoot. She covered her face, then rolled under their legs toward an open doorway, narrowly escaping being crushed as she nudged the door closed behind her. She stayed on the ground for a moment, curled into a ball with her face still in her hands. When she regained her composure, she stretched herself out, staggered to stand, and opened her eyes.