“Contact broken,” the mathematics said.

“For Christ’s sake,” Seria Mau told it, “I could work that out on my own.”

Over the next two days the apparition reappeared at intervals of a minute or two in different parts of the ship, caught by the drifting cameras as a brief subliminal flicker. The shadow operators drove it into corners, where it became panicked. Eventually it flickered to life in front of Seria Mau’s tank, from which position, stabilising quickly but still too small, it regarded Seria Mau patiently from its cluster of eyes and made several attempts to speak.

Seria Mau eyed it with distaste.

“What?” she said.

Eventually it managed to say her name:

“Seria Mau Genlicher, I—” Interference. Static. Echoes of nothing, with nothing to echo in. “—important to warn you about your position,” it said, as if completing some argument she had missed the beginning of. The signal faded, then blurted back loudly. “—modified the Dr. Haends package,” it said, and was silent again. It faded into brown smoke, moving its palps agitatedly: but if it was trying to communicate further, she couldn’t hear. When it had gone, Seria Mau asked the mathematics:

“What are they doing back there?”

“Nothing new. The Moire pod has lost way a little. Touching the Void is still phaselocked to an unknown K-ship.”

“Can you make any sense of this?”

“I don’t think so,” the mathematics admitted.

What does an alien think anyway? What use does it make of the world? As soon as they arrived on a planet the Nastic turned its indigenous population over to excavation projects. They wanted silos, a mile across and perhaps five miles deep. After the lithosphere was laced with these structures, the Nastic would hover by the million in the air above them, on wings which looked as cheap and brand-new as a plastic hairslide. No one knew why, although the best guess was that it had religious significance. If you tried to hold more than a practical conversation with a Nastic, it began saying things like, “The work fails only when the worker has turned from the wheel,” and, “In the morning, they face inward like the Moon.” The Nastic colonies, substantial in number, spread from the rim of the galaxy towards its centre, in the shape of a slice from a pie chart. The inference was obvious: they had originated from outside. That being so, no one could suggest how they had travelled the distances involved. Their own myths, in which the Urswarm travelled without ships at all, beating its wings down some lighted fracture in the continuum, alternately warmed and fried by radiation, could be discounted.

There were no more attempts at communication. The White Cat fled through empty space, while her pursuers hung back like cunning hounds. It was no easier to work out what to do.