She is walking a street in Lagos, Nigeria, passing through a plaza near the waterfront, gleaming white hotels rising around her on all sides—a fountain caught mid-spray, forty coconut palms growing from black-and-white checkered planters—when she stops. She peers up, a faint prickling at the base of her neck: something not quite right.

In Farm 4 Father has a single coconut in a cold-storage drawer. All seeds, he said, are voyagers, but none more intrepid than the coconut. Dropped onto beaches where high tides can pick them up and carry them to sea, coconuts, he said, regularly crossed oceans, the embryo of a new tree safe inside its big fibrous husk, twelve months of fertilizer provisioned on board. He handed it to her, vapor rising from its shell, and showed her the three germination pores on the bottom: two eyes and a mouth, he said, the face of a little sailor whistling its way around the world.

To her left a sign says, Welcome to the New Intercontinental. She steps into the shade of the palms and continues squinting up when the trees ribbon away, her Vizer retracts from her eyes, and Father is there.

She feels the familiar lurch of motion sickness as she steps off her Perambulator. It’s NoLight already. Mother sits on the edge of her bunk working sanitizing powder into the folds of her palms.

“I’m sorry,” Konstance says, “if I was in there too long.”

Father takes her hand. His white eyebrows bunch. “No, no, nothing like that.” The only illumination comes from the lavatory light. In the shadows behind him she can see that Mother’s usually orderly stack of worksuits and patches has been upended, and her button bag is spilled everywhere—buttons under her bunk, under the sewing stool, in the curtain track around the commode.

When Konstance looks back up at her father, some part of her understands before he speaks what he will say, and she feels so acutely that they have left their planet and star behind, that they move at impossible speeds through a cold and silent void, that there is no turning around.

“Zeke Lee,” he says, “is dead.”

One day after Ezekiel’s death, Dr. Pori dies, and Zeke’s mother has reportedly lost consciousness. Twenty-one others—one quarter of the people on board—are experiencing symptoms. Dr. Cha spends her every hour tending to crew members; Engineer Goldberg works through NoLight in the Biology Lab trying to solve it.

How does a plague start inside a sealed disc that has had no contact with any other living thing for almost six and a half decades? Is it spreading via touch or spittle or food? Via the air? The water? Was deep-space radiation penetrating the shielding and damaging the nuclei of their cells, or was it something asleep in someone’s genes, all these years, suddenly waking up? And why can’t Sybil, who knows all things, solve it?