Mei?” Miss Carrie said. “Please put your painting work away now. Your mother is here.”

It took her a few seconds to understand what the teacher was saying, not because Mei didn’t know the words-she was four now, and not a toddler anymore-but because they didn’t fit with the world as she knew it. Her mother couldn’t come get her. Mommy had left Ganymede and gone to live on Ceres Station, because, as her daddy put it, she needed some mommy-alone-time. Then, her heart starting to race, Mei thought, She came back.

“Mommy?”

From where Mei sat at her scaled-down easel, Miss Carrie’s knee blocked her view of the coatroom door. Mei’s hands were sticky with finger paints, red and blue and green swirling on her palms. She shifted forward and grabbed for Miss Carrie’s leg as much to move it as to help her stand up.

“Mei!” Miss Carrie shouted.

Mei looked at the smear of paint on Miss Carrie’s pants and the controlled anger on the woman’s broad, dark face.

“I’m sorry, Miss Carrie.”

“It’s okay,” the teacher said in a tight voice that meant it wasn’t, really, but Mei wasn’t going to be punished. “Please go wash your hands and then come put away your painting work. I’ll get this down and you can give it to your mother. It is a doggie?”

“It’s a space monster.”

“It’s a very nice space monster. Now go wash your hands, please, sweetheart.”

Mei nodded, turned, and ran for the bathroom, her smock flapping around her like a rag caught in an air duct.

“And don’t touch the wall!”

“I’m sorry, Miss Carrie.”

“It’s okay. Just clean it off after you’ve washed your hands.”

She turned the water on full blast, the colors and swirls rushing off her skin. She went through the motions of drying her hands without caring whether she was dripping water or not. It felt like gravity had shifted, pulling her toward the doorway and the anteroom instead of down toward the ground. The other children watched, excited because she was excited, as Mei scrubbed the finger marks mostly off the wall and slammed the paint pots back into their box and the box onto its shelf. She pulled the smock up over her head rather than wait for Miss Carrie to help her, and stuffed it into the recycling bin.

In the anteroom, Miss Carrie was standing with two other grown-ups, neither of them Mommy. One was a woman Mei didn’t know, space monster painting held gently in her hand and a polite smile on her face. The other was Doctor Strickland.

“No, she’s been very good about getting to the toilet,” Miss Carrie was saying. “There are accidents now and then, of course.”

“Of course,” the woman said.

“Mei!” Doctor Strickland said, bending down so that he was hardly taller than she was. “How is my favorite girl?”

“Where’s-” she began, but before she could say Mommy, Doctor Strickland scooped her up into his arms. He was bigger than Daddy, and he smelled like salt. He tipped her backward, tickling her sides, and she laughed hard enough that she couldn’t talk anymore.

“Thank you so much,” the woman said.

“It’s a pleasure to meet you,” Miss Carrie said, shaking the woman’s hand. “We really love having Mei in the classroom.”

Doctor Strickland kept tickling Mei until the door to the Montessori cycled closed behind them. Then Mei caught her breath.

“Where’s Mommy?”

“She’s waiting for us,” Doctor Strickland said. “We’re taking you to her right now.”

The newer hallways of Ganymede were wide and lush and the air recyclers barely ran. The knife-thin blades of areca palm fronds spilled up and out from dozens of hydroponic planters. The broad yellow-green striated leaves of devil’s ivy spilled down the walls. The dark green primitive leaves of Mother-in-Law’s Tongue thrust up beneath them both. Full-spectrum LEDs glowed white-gold. Daddy said it was just what sunlight looked like on Earth, and Mei pictured that planet as a huge complicated network of plants and hallways with the sun running in lines above them in a bright blue ceiling-sky, and you could climb over the walls and end up anywhere.

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.

But this time, Doctor Strickland didn’t ask any of that. The corridors they went down got older and thinner until the woman had to walk behind them so that the men coming the other direction could pass. The woman still had Mei’s painting in her hand, rolled up in a tube so the paper wouldn’t get wrinkles.

Doctor Strickland stopped at an unmarked door, shifted Mei to his other hip, and took his hand terminal out of his pants pocket. He keyed something into a program Mei had never seen before, and the door cycled open, seals making a rough popping sound like something out of an old movie. The hallway they walked into was full of junk and old metal boxes.

“This isn’t the hospital,” Mei said.

“This is a special hospital,” Doctor Strickland said. “I don’t think you’ve ever been here, have you?”

It didn’t look like a hospital to Mei. It looked like one of the abandoned tubes that Daddy talked about sometimes. Leftover spaces from when Ganymede had first been built that no one used anymore except as storage. This one had a kind of airlock at the end, though, and when they passed through it, things looked a little more like a hospital. They were cleaner, anyway, and there was the smell of ozone, like in the decontamination cells.

“Mei! Hi, Mei!”

It was one of the big boys. Sandro. He was almost five. Mei waved at him as Doctor Strickland walked past. Mei felt better knowing the big boys were here too. If they were, then it was probably okay, even if the woman walking with Doctor Strickland wasn’t her mommy. Which reminded her…

“Where’s Mommy?”

“We’re going to go see Mommy in just a few minutes,” Doctor Strickland said. “We just have a couple more little things we need to do first.”

“No,” Mei said. “I don’t want that.”

He carried her into a room that looked a little like an examination room, only there weren’t any cartoon lions on the walls, and the tables weren’t shaped like grinning hippos. Doctor Strickland put her onto a steel examination table and rubbed her head. Mei crossed her arms and scowled.