And when Pirius stepped onto the bare ice, he thought he heard music. He stopped, surprised. The ground throbbed with a bass harmonization he could feel in his chest. It was as if he heard the frozen planet’s beating heart.

Mara smiled. “Wait and see,” she said.

They reached the shallow breast of the ridge. Pirius saw now that the ridge was one of a line of shallow, eroded hills that circled a basin. It was a crater, he realized, but clearly a very ancient one. Though the floor was cracked and tumbled, its unevenness was worn down almost to smoothness. Over perhaps billions of years, the remnants of the great scar had sublimated away, the icy hillocks of its rim relaxed to shallowness, and the invisible hail of cosmic rays had battered at the crust, turning it blood red, like the ice of Port Sol.

And Pirius saw what he had been brought to witness. On the floor of this palimpsest of a crater nestled a city.

At first all Pirius could make out was a pale, scattered sparkle, as if stars from the silent sky had fallen down to the ice. Then he realized he was seeing the reflections of the stars, returned from silvered forms that nestled on the crater floor.

He tapped his faceplate to increase the magnification. The basin was covered by reflective forms, like mercury droplets, glistening on a black velvet landscape. It was a forest of globes and half- globes, anchored by cables. Necklaces swooped between the globes, frosted with frozen air. A city, yes, obviously artificial, and presumably the source of the deep harmonics that traveled to him through the ice. But it wasn’t a human city, and as the ground throbbed beneath his feet, Pirius felt his heart beat faster in response.

Every child in every cadre in every colony across the Galaxy would have recognized this city for what it was, and who must have built it. Every child grew up learning all there was to know about mankind’s greatest enemy save the Xeelee — long vanquished, scattered, its worlds invested and occupied, its facilities destroyed, and yet still a figure of legend and nightmare.

Pirius sensed something behind him, something massive. He turned slowly.

He found himself facing a silvered sphere perhaps two meters across. Pirius could see his own reflection, a bipedal figure standing on blood-dark ice, distorted in the sphere’s belly, and Sol cast a flaring highlight. The sphere hovered without support above the ice, wafting gently as if in some intangible breeze. Its hide was featureless, save for an equipment belt slung around its equator.

Draq stood alongside the sphere, which loomed over him, and slapped its hide. “Now, sirs — what do you think of that? Isn’t it a magnificent beast?”

It was a Silver Ghost. Pirius wished he had a weapon.

The Commissary, taller and bulkier than any of the Plutinos, drew himself up to his full height. Pirius wondered if he had pumped up his Virtual a little for effect. Nilis seemed coldly furious. “Curator Draq, I thought Ghosts had been driven to extinction.”

“Evidently not,” Pirius growled. Mara looked at him uneasily.

Draq gazed at the Ghost’s hide. “Look at this stuff! A Ghost’s skin is the most reflective material in the known universe — and so the most effective heat trap, of course. But it is actually technological. It contains what we call a Planck-zero layer, a sandwich around a zone where the very constants of physics have been tweaked. And the Ghosts incorporated that technology into their own biology. Remarkable: at one time, every living Ghost went about its business clad in a shell that was effectively part of another universe!”

Mara, standing by the Ghost, actually stroked its hide. Pirius thought her gesture was soft, perhaps meant to be reassuring — reassuring to the Ghost.

Pirius’s confusion deepened further. “Commissary, this is a Silver Ghost. It shouldn’t even exist, let alone be bouncing around on Pluto!”

Draq was intimidated by a Commissary, but evidently not by a kid like Pirius. He even seemed triumphant. “We’ve done this to further the goals of the Coalition, Ensign. To serve the Third Expansion!”

Nilis turned on him. “But the boy’s right, curator.”

Draq’s restless hands, encumbered by his skinsuit gloves, wriggled and pulled at each other. “But can’t you see — that’s the sheer excitement of the project. The Ghosts were of course wiped out. But perhaps you know that the Ghosts were composite creatures — each of them symbiotic communities, comprising many living beings, some from worlds alien to the Ghosts themselves, and with their technology merged into their structure, too. And their technologies were simply too useful. For example, hides like this are grown on controlled farms across the Galaxy. Strange to think that bits of what might have been Ghosts are at work, in the service of mankind, all across the Galaxy. If we had been defeated, perhaps the Ghosts would use human leg muscles and livers, hearts, and bones in their machinery!

“And so when, ah, the decision was made that the Ghosts themselves should be revived, under controlled conditions of course, it wasn’t hard to reassemble a self-sustaining community. They are quite at home here, on Pluto; perhaps you know they came from a chill world, colder than Pluto, and their technology, what we’ve been able to recover, serves them well.”

“But why?”

“Because Ghosts are a valuable resource.”

Ghosts were… strange.

Early in their history, their sun had failed, their world had frozen. The universe had betrayed them, literally — and this had taught them that the universe contained design flaws. And so their science turned to fixing those flaws. They ran experimental programs of quite outrageous ambition. Humans certainly had cause to fear them, before they were crushed.

Draq said, “Long ago, the Coalition councils decided that the Ghosts’… ah, ingenuity should be revived — put to use as an engine of ideas, a resource for the benefit of mankind. This was done over and over with other races during the Assimilation, you know. Why not the Ghosts?”

Pirius said, “A resource you had to conceal.”

“Yes! For security — both for humanity’s protection from the Ghosts, and vice versa. And for deniability, I won’t pretend that isn’t true. But you’re here for the Ghosts, whether you know it or not, Commissary. The gravastar idea is theirs—”

Mara said coldly, “This ’valuable resource’ can talk.”

The Ghost hovered impassively. There was no change in its appearance, yet the grammar of the group changed. Suddenly the Ghost stopped being an object, but became a person, a contributor to the conversation.

Nilis walked up to the silvered hide, his Virtual projection casting a blurred reflection on the Ghost’s belly. “It can talk, can it? I see it has a translator box on that belt.” He stood before the Ghost, hands on hips. “You! Ghost!”

Mara said, “There’s no need to shout, Commissary.”

Nilis said, “Do you have a name?”

The Ghost’s voice was synthetic, a neutral human-female voice generated by the translator box it carried, and transmitted to their receiving gear. “I am known as the Ambassador to the Heat Sink.”

Nilis seemed startled. He prodded the Ghost’s hide, but his Virtual finger slid into the reflective surface, shattering into pixels. “And do you know the meaning of the name?”

“No,” the Ghost said bluntly. “I am a reconstruction. A biological echo of my forebears. We have records, but no memory. There can be no true cultural continuity.”

Nilis nodded coldly. “Despite all our ingenuity, extinction is forever.”

“Yes,” the Ghost said simply.

Mara’s expression was dark. “What do you think now, Ensign?”

Pirius spoke without thinking about it. “The Ghosts killed millions of us.” He faced the Ghost. “I’m glad you are conscious. I’m glad you know about the elimination of your kind. I am glad you are suffering.”