She goes back to her computer to fill out his prescription. As she types, she sees him reflected in the screen, looking around at her walls: the star chart behind his chair; the copy of the Hippocratic Oath in the original ancient Greek (her father’s passive-aggressive way of saying that if she was going into medicine, she should have become a doctor); the picture of her and Jules kissing at the Christopher Street Day parade. Mr. López is from a different generation, a different culture, and she’s worried he’ll make a comment. But when he speaks, the question isn’t what she expected. “What are you singing?”

Thora didn’t realize she was humming again. “Just—a tune that’s been in my head. I don’t know where it’s from. Why, do you know it?”

Mr. López doesn’t answer. When she turns to give him his prescription, he has a strange look on his face, as if there’s something he wants to say to her. Instead, his head turns back to the star chart: her public secret, daring the curious to ask. Thora follows his gaze, wondering how to explain to him that she keeps it as an anchor, to manage the vertigo she feels when she looks up at the night sky and imagines a dozen other ways it could have been. These are the stars. This is your life. These were your choices.

“I used to think I would go there someday,” he says, tapping the chart somewhere light-years away.

Thora sees the pain in his eyes and greets it like a friend. In a few decades, she will be the age he is now: an old woman, Earthbound her whole life. “Me too,” she says.

He takes the prescription from her. “It may be selfish, but I’m glad you didn’t,” he says. “Or you wouldn’t have been here to be my doctor.”

“I’m not—” she begins.

“I know.” He gets to his feet, wincing. His hand goes to the back of his neck.

“Something new?” she asks.

He shakes his head. “I’ve had this pain all my life. This is beyond even your power to fix.”

She smiles ruefully as he goes to the door. On the point of leaving, he pauses.

“Was there something else?” Thora asks.

Mr. López frowns, as if he’s not sure what he’s going to say until he says it. “When you said you don’t recognize the world. What do you mean?”

“I mean . . .” She pauses. The appointment is over: she has a cancellation straight after, but Mr. López doesn’t know that. She should really stop talking, send him home. But his eyes are fixed on her, and she doesn’t know why, but she wants to share this with him. “I remember it being better.”

He lets go of the door handle. “Better how?”