Hiram pointed to the pieces of equipment. “That’s a wormhole generator. It’s squeezed-vacuum technology, but far in advance of anything you’ll find on the market. I want to make wormholes bigger and more stable — much more, more than anything anybody’s achieved so far. Wide enough to act as conduits for significant amounts of energy.

“And the energy we mine will be passed through this equipment, the heat exchanger and the turbine, to extract usable electrical energy. Simple, nineteenth-century technology — but that’s all I need as long as I have the energy flow. This is just a test rig, but enough to prove the point of principle, and to solve the problems — mainly the stability of the wormholes.”

“And where,” Bobby said slowly, “will you mine the energy from?”

Hiram grinned and pointed to his feet. “From down there. The core of the Earth, son. A ball of solid nickel-iron the size of the Moon, glowing as hot as the surface of the sun. All that energy trapped in there since the Earth formed, the engine that powers the volcanoes and earthquakes and the circulation of the crust plates… That’s what I’m planning to tap.

You see the beauty of it? The energy we humans burn up, here on the surface, is a candle compared to that furnace. As soon as the technical guys solve the wormhole stability problem, every extant power-generating business will be obsolete overnight. Nuclear fusion, my hairy arse. And it won’t stop there. Maybe some day we’ll learn how to tap the stars themselves. Don’t you see, Bobby? Even the WormCam was nothing compared to this. We’ll change the world. We’ll become rich -”

“Beyond the dreams of avarice,” Bobby murmured.

“Here’s the dream, boy. This is what I want us to work on together. You and me. Building a future, building OurWorld.”

“Dad.” Bobby spread his free hand. “I admire you. I admire what you’re building. I’m not going to stop you. But I don’t want this. None of this is real — your money and your power — all that’s real is me. Kate and me. I have your genes, Hiram. But I’m not you. And I never will be, no matter how you try to make it so…”

And as Bobby said that, links began to form in Kate’s mind, as they used to as she neared the kernel of truth that lay at the heart of the most complex story.

I’m not you, Bobby had said.

But, she saw now, that was the whole point.

As she drifted in space, Mary’s mouth was open wide. Smiling, David reached out, touched her chin and closed her jaw. “I can’t believe it,” she said.

“It’s a nebula,” he said. “It’s called the Trifid Nebula, in fact.”

“It’s visible from Earth?”

“Oh, yes. But we are so far from home that the light that set off from the nebula around the time of Alexander the Great is only now washing over Earth.” He pointed. “Can you see those dark spots?” They were small, fine globules, like drops of ink in coloured water. “They are called Bok globules. Even the smallest of those spots could enclose the whole of our Solar System. We think they are the birthplaces of stars; clouds of dust and gas which will condense to form new suns. It takes a long time to form a star, of course. But the final stages — when fusion kicks in, and the star blows away its surrounding shell of dust and begins to shine — can happen quite suddenly.” He glanced at her. “Think about it. If you lived here — maybe on that ice ball below us — you would be able to see, during your lifetime, the birth of dozens, perhaps hundreds of stars.”

“I wonder what religion we would have invented,” she said.

It was a good question. “Perhaps something softer. A religion dominated more by images of birth than death.”

“Why did you bring me here?”

He sighed. “Everybody should see this before they die.”

“And now we have,” Mary said, a little formally. “Thank you.”

He shook his head, irritated. “Not them. Not the Joined. You, Mary. I hope you’ll forgive me for that.”

“What is it you want to say to me, David?”

He hesitated. He pointed at the nebula. “Somewhere over there, beyond the nebula, is the centre of the Galaxy. There is a great black hole there, a million times the mass of the sun. And it’s still growing. Clouds of dust and gas and smashed-up stars flow into the hole from all directions.”

“I’ve seen pictures of it,” Mary said.

“Yes. There’s a whole cluster of stapledons out there already. They are having some difficulty approaching the hole itself; the massive gravitational distortion plays hell with wormhole stability.”

“Stapledons?”

“WormCam viewpoints. Disembodied observers, wandering through space and time.” He smiled, and indicated his floating body. “When you get used to this virtual-reality WormCam exploration, you’ll find you don’t need to carry along as much baggage as this.

“My point is, Mary, that we’re sending human minds like a thistledown cloud out through a block of spacetime two hundred thousand light years wide and a hundred millennia deep: across a hundred billion star systems, all the way back to the birth of humanity. Already there’s more than we can study even if we had a thousand times as many trained observers — and the boundaries are being pushed back all the time.

“Some of our theories are being confirmed; others are unsentimentally debunked. And that’s good; that’s how science is supposed to be. But I think there’s a deeper, more profound lesson we’re already learning.”

“And that is.”

“That mind — that life itself — is precious,” he said slowly. “Unimaginably so. We’ve only just begun our search. But already we know that there is no significant biosphere within a thousand light years, nor as deep in the past as we can see. Oh, perhaps there are microorganisms clinging to life in some warm, slime-filled pond, or deep in the crevices of some volcanic cleft somewhere. But there is no other Earth.

“Mary, the WormCam has pushed my perception out from my own concerns, inexorably, step by step. I’ve seen the evil and the good in my neighbour’s heart, the lies in my own past, the banal horror of my people’s history.

“But we’ve reached beyond that now, beyond the clamour of our brief human centuries, the noisy island to which we cling. Now we’ve seen the emptiness of the wider universe, the mindless churning of the past. We are done with blaming ourselves for our family history, and we are beginning to see the greater truth: that we are surrounded by abysses, by great silences, by the blind working-out of huge mindless forces. The WormCam is, ultimately, a perspective machine. And we are appalled by that perspective.”

“Why are you telling me this?”

He faced her. “If I must speak to you — to all of you — then I want you to know what a responsibility you may hold.

“There was a Jesuit called Teilhard de Chardin. He believed that just as life had covered the Earth to form the biosphere, so mankind — thinking life — would eventually encompass life to form a higher layer, a cogitative layer he called the noosphere. He argued that the rough organization of the noosphere would grow, until it cohered into a single supersapient being he called the Omega Point.”

“Yes,” she said, and she closed her eyes.

“The end of the world: the wholesale internal introversion upon itself of the noosphere, which has simultaneously reached the uttermost limit of its complexity and centrality.”

“You’ve read de Chardin?”

“We have.”

“It’s the Wormwood, you see,” he said hoarsely. “That’s my problem. I can take no comfort from the new nihilist thinkers. The notion that this tiny scrap of life and mind should be smashed — at this moment of transcendent understanding — by a random piece of rock is simply unacceptable.”

She touched his face with her small young hands. “I understand. Trust me. We’re working on it.”