Perhaps Nilis had been right that he needed a break. But Nilis had not been able to see that being on Earth, alone, was precisely the wrong kind of rest cure for a Navy brat. He longed for Torec, his only point of familiarity in this strange solar system. But she was out at Saturn. He was able to speak to her; Nilis even let him use expensive inseparability channels, so there was no time delay. But it wasn’t the same. He needed to be touched, held.

And anyhow even Torec seemed cold.

After forty-eight sleepless hours he called Nilis. He begged to be brought out to Saturn and put back to work.

Pirius arrived in time for a test firing of what Nilis called the “Callisto weapon.”

He was brought to Nilis’s corvette, which the Commissary was using as his work base. The interior was cluttered, with data desks strewn on the floor, bots of all sizes tumbling through the air, and Virtuals obscuring every view. Nilis was here, with Commander Darc, Torec, and various assistants. In this noisy mess it was impossible to see how any work got done. Nilis and Darc seemed to be working closely, but their arguments crackled like lightning.

Pirius spotted Torec, peering out at the test rig. He made straight for her. He hadn’t seen her for weeks, since before Venus. She acknowledged him with a nod, but turned away. He stood awkwardly, arms suddenly heavy, longing to touch her. He just didn’t understand.

He pulled himself together. He stood with her and looked out of the hull.

Orbiting far from Saturn’s patient golden face, the test rig was a set of twenty GUTdrive engines, mounted in a loose spherical framework perhaps fifty meters across. Technicians and bots crawled over it. It had been put together in a few days, and it didn’t look much like anything, let alone a weapon for striking at the most formidable fortress in the Galaxy.

But a few kilometers away, the captive Xeelee ship waited, surrounded by its usual cordon of watchful guardian drones; today, once again, the nightfighter was the test target. Spinning slowly, surrounded by its attendant cloud of bots and techs, the test rig looked as much a threat to the patient Xeelee as a spitball.

He said, “It looks like shit.”

Even that didn’t force a smile from Torec. “Actually we’ve come a long way in a few days. But we’re as underfunded as ever. We need GUTdrive generators, but all Nilis was able to get hold of are those dinged-up, decommissioned relics. You can see the scars where they have been cut out of wrecks.”

“Darc and Nilis are at each other’s throats.”

“That’s just their way. Darc is keen, once he forgets that he disapproves of the whole thing. He likes getting his hands dirty — especially on something new like this. He’s okay.”

Pirius looked covertly at her so-familiar profile, the finely carved chin, the upturned nose, the lines of her face softened by golden-brown Saturn light. “And you’ve kept busy.”

She shrugged. “It’s not so bad right now. When, if, we get through this proof-of-concept stage, I’ll be involved in developing the flight hardware. You, too, I guess.”

His need to touch her was an ache. “Torec, listen. I—”

She held up a hand, silencing him. A green light flared beyond the hull.

The techs and bots backed away from the rig, leaving only a few drones for close-in monitoring. Pirius watched Torec silently counting down, tracking the clock in her head, as she always did: Three. Two. One.

The rig quivered. Waves of distortion, easily visible, spread out from each of the GUTdrive generators, as if they were pebbles thrown in a pool.

GUTdrive engines worked by allowing a fragment of compressed mass-energy to expand, releasing energy through the decay of a unified superforce. In this configuration, rather than using that energy to drive a spacecraft, the engines were each supposed to create a spherical wave of distorted spacetime. The engines had been positioned so that the ripples moved inward, into the rig.

As the waves converged, blue-white light flared, dazzling. The flash dissipated immediately — but now a concentrated knot of distortion was traveling along the axis of the rig. Shifting, oscillating, the distortion made the stars blur as it traveled. It was like an immense drop of water, Pirius thought. As it burst from the rig the knot broke open struts, and sent the scavenged GUTdrive engines flying — and it was aimed straight at the nightfighter.

But before it had traveled more than a few hundred meters, the ball of distortion swelled up, burst silently, and dissipated.

There was a rustle of movement in the corvette, a collective sigh of disappointment.

Darc clapped Nilis on the back. “Scratch another run. Never mind, Commissary. We’re not done yet.”

“Indeed not.”

Torec said to Pirius, “Timing is everything. The implosion in the center is what we’re trying to design. If the amplitude is large enough, you get nonlinearity — a shock wave, its profile distorting as it travels, what the techs call a ’classical scalar wave.’ I think we’ve got the amplitudes right, but not the timing. If the waves don’t converge right at the center, they just pass through each other harmlessly.”

Pirius said, “And if the timing is right — what’s supposed to happen?”

Torec stared at him, the first time she’d looked at him directly since he had got here. “You were on Callisto, and you don’t know?”

Pirius said helplessly, “I just did my job there.”

“This is a design from the Occupation era. It’s a black-hole cannon, Pirius.” She smiled faintly. “Can you believe that? We’re making a cannon to fire black holes at the Xeelee. And you know what else? It was designed by Friends. Friends, just like Enduring Hope!”

Pirius, stunned, stared at the battered test rig. The techs and drones were already going back to work.

Nilis asked Pirius to spend some time with him.

They sat together in Nilis’s cabin. It was clear to Pirius that the Commissary wanted something. But Nilis was still guilty about how Pirius had been “used” on Callisto, and he seemed to want to make it up to him by talking to him.

He said his “Callisto weapon” did indeed date from the time of the Qax Occupation. Pirius was amazed that the Friends of Wigner, in his day an illegal fringe cult out on Arches, had roots that deep.

Back then the Friends had been a group of rebels on Earth. During the early phase of the Occupation, the control of the Qax had been relatively light — and remarkably enough, the Friends had been able to assemble a whole spacecraft, equipped with black-hole cannons, under the noses of Earth’s occupiers.

The Friends had known that a wormhole bridge to the deeper past was soon to be opened; spanning fifteen centuries, this audacious stunt had been set up by none other than Michael Poole. When the bridge opened, the Friends hurled themselves and their ship into the past. Ignoring the humans of Poole’s time, they had set to work preparing their battery of black holes — but their purpose was not to use their cannon as weapons. Their target was Jupiter. In the guts of the gas giant these grenades of twisted spacetime would collide and merge, each collision sending out pulses of gravitational waves. By programming this sequence, the Friends hoped to shape the collapse of Jupiter, and so sculpt the final black hole that would result.

“So that was what happened to Jupiter,” Pirius said.

“Yes. Quite a monument!”

“But if they could make black-hole cannons, if they could go back in time, why not just fly out to the Qax home world and wipe them out?”

Nilis smiled. “Spoken like a true pragmatist! But the Friends’ objective was more philosophical…”

The first Friends of Wigner had taken their name from an ancient philosopher who had pondered the mysteries of quantum physics. Beneath the world perceived by humans was a scaffolding of uncertainty. Quantum functions pervaded space, each a description of the probability governing a particle or system; it was only when an observation was made that a particle could be pinned down to a particular place, or to a definite speed.