Then Pirius saw it. “This is a cruiser,” he breathed. “A Ghost cruiser.” Once, millions of ships like this had patrolled the Orion Line, the Ghosts’ great cordon flung across the face of the Galaxy.

The Ghost ship was kilometers long, big enough to have dwarfed the greenship Pirius’s future self would have piloted in the Core. It had nothing like the lines of a human craft. The cruiser was a tangle of silvery rope within which bulky equipment pods were suspended, apparently at random.

And everywhere there were Silver Ghosts, sliding along the silver cables like beads of mercury.

“Of course it’s just a mock-up,” Mara said. “Basically life support. There are no drive units; it can’t fly. And no weapons! I always think it looks more like a forest than a ship. But that’s what it is, in a sense. The Ghosts are like miniature ecologies themselves, and they turned slices of their ecology into their ships. I’ve always thought that was a much more elegant solution than our own clunky mechanical systems.”

Pirius felt that deep anger welling again. “Millions of human lives were lost in the defeat of ships like this. And you’ve built a, a monument to our enemy.”

“Yes,” she said testily. “As you’ve said before. But don’t you think we need to understand what it was we killed?”

He thought he didn’t understand her at all. “Is that why you’re here? Were you always so curious about Ghosts?”

She hesitated, perhaps wary of giving away too much of herself. “I suppose so—yes. I’ve always been a Commissary. I started in the Office of Doctrinal Responsibility: very dry work! I was always blighted by curiosity. Not a good characteristic in the Commission for Historical Truth.” Her smile, behind her visor, was thin. “Then I found out about this facility, and a number of others, where life-forms generally supposed lost during the Assimilation have been preserved—or, as in the case of the Ghosts, revived.”

“There are others? . . . Never mind. How did you find out?”

She smiled again. “The control of the Commission isn’t as complete as some like to imagine. Truth finds a way. So I volunteered to come here. The powers that be were surprised, but they processed my application. Pluto is generally a punishment detail, you know. You come here to make amends, to end your career—certainly not to progress it.”

“And was it worth it?”

“Oh, yes, Ensign. It was worth it.” She led him around the periphery of the mocked-up cruiser. “I mean, look at this. What’s fascinating about the Ghosts to me isn’t their technological capabilities but their story: their origin, their account of themselves. You know, the Ghosts call the sky the Heat Sink—the place the heat went.” Since their world had frozen, Mara said, the Ghosts had not been shaped by competitive evolution, as humans had, but by cooperation. “They are symbiotic creatures. They derive from life-forms that huddled into cooperative collectives as their world turned cold. Every aspect of their physical design is about conserving heat, precious heat.