And beneath that there was a still grander timescale, of the slow evolution of the Moon itself. She thought about all she had seen — the ejecta hills, the rille, the crater-sculpted plains — and she knew that she could have come here a billion years before, or a billion years from now, to find basically the same scene.

The Moon cared nothing for time. And the longer she stayed, the more her own busy schedules came to seem irrelevant. She felt as if her sense of time was dissolving, stretching like melted candle-wax. Perhaps she could sink down into the Moon’s rhythms. Perhaps if she kept still, she could lie here long enough for the Moon to turn beneath her, and carry her into the night.

Henry seemed to be sleeping peacefully.

In a way, he had what he wanted. And there was the paradox of a scientist. On one level Henry was satisfied. What had driven him in his feverish efforts earlier — what had driven him all the way to the Moon — wasn’t so much fear for himself, a desire to save those he loved, as simple curiosity. Now, Henry had his answer.

But that was too simple. Henry was no one-dimensional Brainiac. She suspected he understood the Moonseed on a level that defied her. And when he contemplated it — its simplicity of operation, its immense timescales, its tenacity, its capacity to destroy worlds — it seemed he felt genuine awe.

She suspected he envied the Moonseed its lack of the complexity that bedevilled human life. Maybe Henry would like to be a half-machine, like the Moonseed.

But even that wasn’t the bottom of the truth, she thought sadly. Because, plumb in the middle of Henry’s life, there you had dippy Jane, his relationship with her based on nothing but — she forced herself to admit it — love.

Maybe she’d never really understood Henry, she thought. Or vice versa. Probably they’d never stood a chance.

She probed at her own feelings. She felt — numb. Bewildered. Maybe she had gone through too much; maybe she was in shock. How were you supposed to feel, when your ex-husband says your species is doomed?

Geena had grown up, in San Francisco, without religion. She’d never felt the need of what she thought of as its ersatz, manipulative comforts. So she had never had the expectancy of surviving her own death.

More than that: she’d grown up with the message of science, which was that humanity had a finite tenure on the planet, come what may. If nuclear war didn’t get you, the eco-collapse would, or the dinosaur killer, or the return of the glaciers, or the extinction of the sun, or… The doom scenario depended only on which timescale you chose to think about.

She was an advocate of space travel. Colonies off the planet would have boosted mankind’s chances of survival. If NASA’s more grandiose plans had come to pass and there were now, say, three or four hundred people living in some kind of Antarctic-type research station on Mars, right now, they wouldn’t have to worry so much about this Moonseed thing.

The Earth might die. Even the Moon. Mankind wouldn’t have to.

But it was too late for that.

The fact was humans just weren’t adapted to living anywhere away from Earth — the deep gravity well and thick, complex atmosphere they’d evolved in — and there was nowhere else in the Solar System for them to go.

She was glad she didn’t have a kid…

“What are you thinking about?”

Henry’s voice made her jump. He was lying in his sleeping bag, eyes wide in the dark.

“Sorry,” he said.

“I was thinking about the Moon.”

He scratched his couple of days” growth of beard. He never could grow a beard, she thought; it came up comically patchy. He said, “Plutarch said the Moon was a way-station for our souls. Humans have to die twice. First on Earth, where the body is severed from the mind and soul, and returned to dust. And the mind and soul travel to the Moon. There, a second death occurs, with mind and soul separating. The mind flies off to the sun, where it’s absorbed and gives birth to a new soul. But your soul stays here, on the Moon, sinking into the Moon dust, clinging onto dreams and memories… Maybe all that stuff about rocket ships and Cape Canaveral and Baikonur was a fantasy. A false memory. Maybe we died, you and me. Maybe we’re just clumps of memories, sinking into the regolith.”

She was shivering, despite the warmth of the hab.

“Shut up, Henry.”

“Sorry.” He rubbed his face; his patchy beard looked to have grown a little denser.

She felt she couldn’t stand the stillness any longer.

“Henry, for Christ’s sake.”

“What?”

“Tell me your plan.”

He hesitated.

“I haven’t shared this with anybody,” he said.

“Not even dippy Jane?”

“Not even Jane.”

“I promise not to laugh at you. But I could use some good news right now.”

“…I think there’s maybe a way out. It’s risky. The math is chancy; it depends on a lot of assumptions.”

“Like what?”

“How much ice there is at the South Pole. What happens when you drop a nuke on lunar Moonseed; what kind of energy amplification factor you can achieve here, in the presence of the hive remnant—”

“Why didn’t you tell me about it before?”

“I had to get here to be sure. I had to confirm the Moonseed is as extensive as I suspected. And—”

“What?”

“I had to sleep on it.”

“Why?”

He sat up. The sleeping bag fell slowly away from his chest, exposing his longjohns. “There are a lot of costs. Suppose I told you it might be possible to save some of mankind.”

“Not all?”

“Not all. A handful. Maybe enough to start again.”

“Right now, I’d take it.”

“Okay. Now suppose I told you it would mean wrecking the Moon, as it exists now, before we have any kind of chance to study it, to learn from it. Gone forever.”

That made her pause.

“Go on.”

“Suppose I told you it might cost us our lives.” He grinned tightly. “In fact, probably. That’s the part I’ve been sleeping on.”

She closed her eyes. “I guess we’re all soldiers now,” she said. “And this is the front line.”

“Suppose I told you it will certainly cost Arkady his life.”

She kept her face still. “Why?”

“We talked about this. Because somehow Arkady is going to have to deliver that nuke of his to the surface, at the South Pole. It’s kind of hard to see how he can do that without at least stranding himself in orbit. Look, Geena, when I came out here I didn’t know what Arkady meant to you.”

“Would that make a difference now?”

“I don’t know,” he said. “Let’s face it. It’s complicated.”

“Then we must ask Arkady how he feels.”

“Yes,” he said. “Yes, we must.”

“Tell me what you got.”

He opened up his laptop, and started to explain.

And that was how it started.

They got into a complex four-way discussion, involving Houston, Korolyov, Arkady up in orbit, the two of them huddled in their shelter.

The mission planners in Moscow and Houston came up with a way for Arkady to deliver the bomb as Henry asked. It was actually Arkady’s idea. They chewed it over from every which way.

It lasted hours. It involved geologists, orbital mechanics specialists, NASA managers, even politicians.

The plan was wild, implausible, resting on a lot of unproven assumptions. And none of them — Arkady, Geena or Henry — had a hope of living through it, to see if it worked.

But, she slowly realized, they were going to do it anyhow.

Eventually they got the go-ahead. The consensus was, they had little, after all, to lose by trying Henry’s outrageous idea.

Arkady, of course, agreed immediately, as Geena knew he would.

When she thought about it, his proposal was entirely in line with his character. Because it would allow him to become a hero at last: a new Gagarin, transcending the old, the saviour of the planet.