The distinction between machine and weapon was one of intent, and if what Ariana had understood was accurate, if what my mother and Captain Ngahere had deduced was true, this parasite’s goal was to cause destruction. They had understood its danger in terms of the impact of a kilometer-long ship crashing into Earth. But even without the crash, it would be catastrophic for the parasite to get loose on Earth. It would be a pandemic. It would, in fact, be an invasion, because something or somebody—so far away the distance was inconceivable, perhaps so long ago the light by which they worked might exist only as a ghost star in Earth’s sky—somebody had created this thing, and set it free.

It was a discovery the likes of which humanity had never made before. I knew that. I knew it, and there was a part of me that could still feel how exciting it was, how very much it mattered. That part of me that believed my parents had died doing important work, that believed exploring the stars and stretching the reach of humankind into space was a noble and necessary goal. Yesterday I would have happily argued that the search for life and civilization elsewhere in the galaxy outweighed any danger. Maybe it should. Maybe that was the bolder choice. But everywhere on this ship there was a weapon that had, over the space of a single day, made the people of House of Wisdom attack their own bodies with violence and fear, had made my father take his own life with a knife from our kitchen, had turned my mother from an engineer into an architect of mass murder.

On the screen, Brahmin sailed farther and farther away. I turned to Zahra.

“Those things—the parasites—they want to crash the ship into Earth.”

“What?”

“That’s the information Xiomara and Baqir are taking to my aunt. Ten years ago, when the parasite had control of the ship, it had a collision course set. My mum and the captain stopped it.”

“But that would be . . .” She faltered. “Why would it do that?”

“I don’t know,” I said. “I don’t care about its reasons. I know you hate Earth. But I can’t let this thing get anywhere near it. You can help or not. Just don’t try to stop me.”

For a long moment we looked at each other, both of us dirty and bedraggled and shaking with exhaustion. I no longer had any sense of how long I had been awake. Zahra crossed her arms over her chest and shivered, looking absurdly young in the too-large knit sweater, her black hair flying free of its plaits.

She said, “I’ll help. I need to talk to Homestead.”

She turned from the terminal and headed for the door.

ZAHRA