The Superet creed, in some ways, Louise thought, embodied the essence of the pre-Poole optimism of humanity. Superet believed that nothing was beyond the capabilities of mankind.

Poole gazed into his drink. “Superet believes that if something is physically possible, then it’s just a question of engineering.” The Virtual’s expression was complex — almost tormented, Louise thought. The Virtual went on, “But it takes planning — perhaps on immense timescales.”

Louise felt a vague anger build in her. Uvarov was right. This isn’t Michael Poole. Poole would not have defended the grandiose claims of Superet like this. This is a travesty of programming in conflict with sentience.

“In the past,” the Virtual went on, “Superet sponsored many of the eco engineering projects which have restored much of the biosphere of Earth — the carbon-sequestration domes, and so on.”

Louise knew that was true. The great macroengineering projects of the last millennium, supplemented by the nano-engineering of the atmosphere and lithosphere and the transfer offplanet of most power-generating and industrial concerns, had stabilized and preserved Earth’s fragile ecosystem. There was more woodland covering the temperate regions, now, than at any time since the last glaciation, locking in much of the excess carbon dioxide which had plagued previous centuries. And the great decline in species suffered after the industrialization of a couple of thousand years ago had long since been reversed, thanks to the use of genetic archives and careful reconstruction from disparate descendants — of lost genotypes.

Earth had been the first planet to be terraformed.

The Virtual said, “But Superet’s goals were modified, following the Friends of Wigner incident…”

“If Superet is such a saintly organization,” Uvarov growled, “then why is it such a thing of shadows? Why the secrets?”

Poole said, “Superet is a thousand years old, Doctor. No human organization of such longevity has ever been fully open. Think of the great established religions, societies like the Templars, the Masons. Groupings like Superet have a way of accreting tradition, and isolation, around themselves with time.”

“And,” Uvarov said sharply, “no doubt the long career of Superet has a few dark phases…”

Poole didn’t reply.

Louise said, “You said the goals of Superet were changed by the Friends incident.”

“Yes. Let me use this Virtual box of tricks to explain.”

The tetrahedron came to life again. It rotated above them, a gaudy trinket miles across.

“The Cauchy Interface,” the Virtual said. “At the time, the largest wormhole mouth constructed — in fact, the largest exercise in exotic-matter engineering.”

The Virtual’s face was gaunt in the shifting Interface light — wistful, Louise thought.

Michael Poole had been rightly celebrated for his achievements, she thought. He had been the Brunel of his day, and more. His wormhole projects had opened up the System much as the great railroads had opened up Great Britain two thousand years earlier.

A wormhole was a flaw in spacetime — a throat, connecting two events in spacetime that would otherwise be separated by light-years, or millennia. Wormholes existed naturally on all scales, most of them around the size of the Planck length — ten to minus forty three inches, the level at which space itself became granular.

Working in the orbit of Jupiter, Michael Poole and his team had taken natural wormholes and expanded them;

Poole had made wormholes big enough to permit spaceships to pass through.

Wormholes were inherently unstable. Poole had threaded his wormholes with frameworks of exotic matter — matter with negative energy density, with pressure greater than rest mass energy. The exotic matter set up repulsive gravity fields able to hold open the wormholes’ throats and mouths.

Louise remembered the excitement of those times. Poole Interfaces were towed out of Jovian orbit and set up all over the System. The wormholes enabled the inner System to be traversed in sublight GUTships in a matter of hours rather than months. The Jovian system became a hub for interplanetary commerce. Port Sol — a converted Kuiper object on the rim of the System — was established as the base for the first great interstellar voyages.

Michael Poole had opened up the Solar System in an explosion of accessibility, more dramatic than anything since the days of the great sea-going voyages of exploration on old Earth.

“It was a wonderful time. But you had greater ambitions in mind,” she said. “Didn’t you, Michael?”

The Virtual stared upwards at the display above, expression frozen, evidently unable to speak.

Mark said gently, “You mean the Cauchy, Louise?”

“Yes. Michael Poole used wormhole technology to travel — not just across space but across time.” She pointed up to the tetrahedron in the dome. “This is just one Interface from Poole’s greatest wormhole project: termini three miles across, and the throat itself no less than a mile wide. The wormhole’s second Interface was attached to a GUT-ship — the Cauchy.”

The GUTship was launched on a subrelativistic flight beyond the fringe of the Solar System — a circular tour, designed to return at last to Jupiter. The Cauchy carried one of Poole’s wormhole Interfaces with it. The other was left in orbit around Jupiter.

The flight lasted fifteen centuries — but thanks to time dilation effects, only two subjective centuries had passed for the Cauchy’s crew.

The two Interfaces remained linked by the wormhole flaw. Because of the link, when it returned to the Solar System more than a millennium into the future of the System it had left, the Cauchy’s Interface was still connected to its twin in orbit around Jupiter — where only two centuries had passed since the departure of the Cauchy, as they had for the Cauchy’s crew.

“By passing through the wormhole,” Louise said, “it was possible to travel back and forth through time. Thus, Poole had used wormhole technology to establish a bridge across fifteen hundred years, to the future.”

Mark pulled at his lips. “We all know what became of this great time bridge. But — I’ve never understood — why did Poole build it?”

The Virtual spoke, his voice tired, dry — so familiar that Louise felt her heart move. Michael Poole said, “It was an experiment. I was more interested in proving the technology — the concepts — than in the final application. But — ”

“Yes, Michael?” Louise prompted.

“I had a vision — a dream perhaps — of establishing great wormhole highways across time, as well as across space. If the technology is possible, why not? What power might be afforded to the human species with the opening up of such information channels?”

“But the future didn’t welcome this great dream,” Uvarov said drily.

“No, it didn’t,” Virtual-Poole said.

The floor of the Hermit Crab’s lifedome turned transparent; space-darkness washed across it in a sudden flood that made Milpitas gasp audibly.

Louise stood and looked down. There was space-emptiness beyond her feet; her eyes told her she was suspended above an immense drop, and she had to summon all her will not to stumble, weakly, back to her chair…

And then, belatedly, she registered what she was seeing: beneath the lifedome, and extending for hundreds of yards in every direction, was a floor of some broken, irregular, bloody material — a floor of (what looked like, but couldn’t possibly be) flesh.

Louise turned slowly around, trying to make out the geometry of what she was seeing.

The flesh-surface, bathed in sickly Jovian light, curved away from her in all directions; the “floor” was actually the outer surface of a sphere — as if the Crab were embedded in an impossible moon of flesh, perhaps a mile wide. If the Crab’s drive section still existed, it was buried somewhere deep inside this immense carcass. The clean metal lines of the GUTship’s spine — which connected lifedome to drive unit — were enveloped in a gaping wound in this floor of flesh.