Amy had stepped away from the group, into the field. For a moment they watched her, moving through the windblown grass.

“Do you think she understands what she did?” Alicia asked.

It was Amy who had blown the coupler. The switch was located in the rear of the engine compartment by the head-end unit. Probably it had been connected to a drum of diesel fuel or kerosene, Michael surmised, with some kind of igniter. That would have been enough to do it. A fail-safe, in case the cars were overrun. It made sense, Michael said, when you thought about it.

Peter supposed it did. But none of them could explain how Amy had known what to do, nor what had led her to actually throw the switch. Her actions seemed, like everything else about her, beyond ordinary understanding. And yet it was because of her, once again, that they were all alive.

Peter watched her for a long moment. In the waist-high grass she appeared almost to float, her hands held out from her sides, grazing the feathered tips. Many days had passed since he’d thought of what had happened in the Infirmary; but watching her now as she moved through the grass, he was washed by the memory of that strange night. He wondered what she had told Babcock when she had stood before him. It was as if she were part of two worlds, one that he could see and one that he could not; and it was within this other, hidden world that the meaning of their voyage lay.

“A lot of people died last night,” Alicia said.

Peter drew a breath. Despite the sun, he felt suddenly cold. He was still watching Amy, but in his mind he saw Mira—the girl’s body pressed to the roof of the train, the viral’s hand reaching for her, pulling her away. The empty space where she had been and the sound of her screams as she fell.

“I think they’d been dead a long time,” he said. “One thing’s for sure, we can’t stay here. Let’s see what we’ve got.”