Mei leaned her head on Doctor Strickland’s shoulder, looking over his back and naming each plant as they passed. Sansevieria trifasciata. Epipremnum aureum. Getting the names right always made Daddy grin. When she did it by herself, it made her body feel calmer.

“More?” the woman asked. She was pretty, but Mei didn’t like her voice.

“No,” Doctor Strickland said. “Mei here is the last one.”

“Chysalidocarpus lutenscens,” Mei said.

“All right,” the woman said, and then again, more softly: “All right.”

The closer to the surface they got, the narrower the corridors became. The older hallways seemed dirtier even though there really wasn’t any dirt on them. It was just that they were more used up. The quarters and labs near the surface were where Mei’s grandparents had lived when they’d come to Ganymede. Back then, there hadn’t been anything deeper. The air up there smelled funny, and the recyclers always had to run, humming and thumping.

The grown-ups didn’t talk to each other, but every now and then Doctor Strickland would remember Mei was there and ask her questions: What was her favorite cartoon on the station feed? Who was her best friend in school? What kinds of food did she eat for lunch that day? Mei expected him to start asking the other questions, the ones he always asked next, and she had her answers ready.

Does your throat feel scratchy? No.

Did you wake up sweaty? No.

Was there any blood in your poop this week? No.

Did you get your medicine both times every day? Yes.