Finally they stop outside the door that reads Vault One. Pale, panting, his face shining with sweat, Father glances back over his shoulder, then presses his palm to the door. Wheels turn and the vestibule opens.

Sybil says, Entering Decontamination Area.

He ushers Konstance inside and sets her Perambulator beside her and braces the stool in the threshold against the door frame.

“Don’t move.”

She sits in the vestibule in the crinkling suit and wraps her arms over her knees and the hood says, Oxygen at twenty-five percent, and Sybil says, Commencing decontamination process. Konstance cries, “Father,” through the mask of her hood, and the outer door closes in its track until it meets the stool.

The legs of the stool bend with a shriek and the door stops.

Please remove blockage in outer door.

Father returns carrying four sacks of Nourish powder, pitches them over the half-crushed stool into the vestibule, and rushes away again.

Next comes a recycling toilet, dry-wipes, a food printer still in its wrapper, an inflatable cot, a blanket sealed in containment film, more sacks of Nourish powder—back and forth Father hurries. Please remove blockage in outer door, repeats Sybil, and the stool crumples another centimeter under the pressure, and Konstance begins to hyperventilate.

Father pitches two more sacks of Nourish powder into the vestibule—why so many?—and steps through the gap in the door and slumps against the wall. Sybil says, In order to begin decontamination you must remove the blockage in the outer door.

Into Konstance’s ear the hood says, Oxygen at twenty-three percent.

Father points to the printer. “You know how to operate that? Remember where the low-voltage line attaches?” He rests his hands on his knees, chest heaving, sweat dripping from his beard, and the stool shrieks against the pressure. She manages to nod.

“As soon as the outer door is closed, close your eyes, and Sybil will flush the air and sterilize everything. Then she’ll open the inner door. Do you remember? When you go inside, bring everything else with you. All of it. Once you have everything inside and the inner door is sealed, count to one hundred, and it should be safe to take off the hood. Understood?”

Fear thrums through every cell in her body. Mother’s empty bunk. The tents in the Commissary.

“No,” she says.

Oxygen at twenty-two percent, says the hood. Try to breathe more slowly.

“When the inner door is sealed,” repeats Father, “count to one hundred. Then you can take it off.” He presses his weight against the edge of the door, and Sybil says, The outer door is blocked, the blockage must be removed, and Father glances out into the darkness of the corridor.

“I was twelve,” he says, “when I applied to leave. All I could see, as a boy, was everything dying. And I had this dream, this vision, of what life could be. ‘Why stay here when I could be there?’ Remember?”