But, Park thought—but if she could just stay by Glenn’s side as much as possible—she could protect him. They could see that he was important. They could see that she cared.

“Be safe,” Park would say to Glenn as he handed over her schoolbag each morning.

“I understand,” he would answer seriously. His classic response. “I understand” was a default programmed phrase, Glenn’s most basic factory setting—practically an instinct, like a baby smiling when you smiled at it, or a dog wagging its tail when you called its name. Essentially an empty verbal cue that indicated that her words had registered, but he had nothing better to say. How much did he really comprehend, rather than simply hear? How much of it was just a ritual, an acknowledgement without deeper knowledge: shadow puppets making gestures at each other from across the wall, but never quite connecting without losing their shapes altogether? Sometimes she said it back to him: “I understand,” and then Glenn said that he understood that she understood, and then Park said that she understood that he understood that she understood, and it became a little game between them, the words stacking up on top of each other like a tower of cards. They formed an echo chamber with each other, their understanding circling overhead, invisibly.

But sometimes he said it and she was afraid that it didn’t mean anything.

But then there were the other times—the times that he would smile at her, faintly, when she told him to be safe. Once or twice Glenn squeezed the tops of Park’s fingers, hard, imparting some hidden meaning that she didn’t try to decode. Then he would turn on his heel and leave. So maybe “I understand” really meant “Goodbye.” Who could know? All she knew was that if she kept giving the command, he kept coming back again, whole. As long as she told Glenn to be safe, he would be. He had to follow orders.