In the Library grown-ups gesticulate around tables while cyclones of documents whirl above them. Mrs. Chen herds the teenagers up a ladder to a table on the second tier and sets an orange volume in the center. Ramón and Jessi Ko and Omicron Philips and Ezekiel’s little brother Tayvon watch as a foot-tall woman in a light-blue worksuit with the word ILIUM stitched on the breast emerges from the book. If at some point during your long voyage, she says, it becomes necessary to quarantine in your compartments, be sure to stick to your routines. Exercise daily, seek out fellow crew members in the Library, and…

Ramón says, “You hear about people vomiting but to actually see it?” and Jessi Ko says, “I hear Quarantine One lasts seven days no matter what,” and Omicron says, “I hear Quarantine Two lasts two months,” and Konstance says, “I hope your brother feels better soon, Tayvon,” and Tayvon bunches his eyebrows like he does when he’s concentrating on a mathematics problem.

Below them Mrs. Chen crosses the atrium and joins grown-ups around a table, images of cells and bacteria and viruses rotating in the space between them. Ramón says, “Let’s go play Ninefold Darkness,” and the four of them scamper up a ladder toward the Games Section, and Konstance watches the flying books a moment longer, then takes a slip of paper from the box in the center of the table, writes Atlas, and drops it into the slot.

“Thessaly,” she says, and drops through the Earth’s atmosphere and floats over the olive-and-rust-colored mountainscape of central Greece. Roadways emerge below, the terrain cut into polygons by fences, hedgerows, and walls, a familiar village coming into view now—cinderblock privacy walls, slate rooftops beneath cliff faces—and she’s walking the cracked pavement of a rural road in the Pindus Mountains.

Side streets split left and right, little dirt thoroughfares branching off those, drawing an elaborate tracery higher into the hills. She climbs past a row of houses built right up to the roadside, a disemboweled car in front of one, a face-blurred man in a plastic chair in front of the next. A houseplant wilts in a window; a sign with a skull on it has been mounted on a pole out front.

She turns right, following a route she knows well. Mrs. Flowers was right: the other kids find the Atlas hilariously obsolete. There’s no jumping or tunneling like in the more sophisticated games in the Games Section: all you do is walk. You can’t fly or build or fight or collaborate; you don’t feel mud grab your boots or raindrops prick your face; you can’t hear explosions or waterfalls; you can hardly leave the roads. And inside the Atlas everything besides the roads is as immaterial as air: walls, trees, people. The only solid thing is the ground.