Something else occurred to him. “Why did you try and make me think that Leda killed Mariel, when you knew the whole time that she hadn’t done it?”

“Leda was always my backup plan. It wasn’t a coincidence that she blacked out that night—I faked messages from her account to her dealer, asking for higher dosages than normal. I wanted to make sure I had someone to take the blame, just in case.”

“Just in case?”

“I tried to wipe away all traces of what I had done, but apparently my hacking left a trace on that transport bot. Three months ago, in a routine maintenance check, someone noticed that the bot had been tampered with. That was why the police moved Mariel’s case from accidental death to murder—because they realized that someone had used a bot to knock Mariel into the water.”

He blinked, feeling betrayed. “You knew that was the reason the case was reclassified, and you never told me?”

“Of course I knew,” Nadia said, her voice clipped. “I didn’t tell you because you never asked me directly. Until now.”

“What does that have to do with Leda?”

“I worried that you would eventually be drawn into the murder investigation. The police might have blamed you for Mariel’s death, or worse, discovered the truth about me. I couldn’t have that.

“So I let you think that Leda might have killed Mariel. I knew that you would ask her point-blank if she had done it. And after you hacked the police station, I led you to believe that the police were getting closer—that the net was drawing tighter around all of you. I wanted Leda to question her own guilt.”

“Why?”

“I knew that if Leda thought you were in danger, she would take the fall to keep you safe. And I was right, wasn’t I?” Nadia added, sounding almost proud. “That’s exactly what Leda was planning to do. The only thing I didn’t foresee was that Avery Fuller would step in and take the blame instead.”

And it didn’t matter to Nadia, Watt realized, fighting back a wave of nauseous grief. One scapegoat was as good as another. Humans were interchangeable to her—except for Watt, the one human she had been programmed to care about.

And it wasn’t as if Nadia herself was about to step forward and confess to the crime.

Watt shook his head. “I still don’t understand. You aren’t supposed to harm humans; that’s your fundamental programming.” He coded that as Nadia’s core directive: the single command that she could never contradict, no matter what subsequent commands were given to her. It was the way all quants were coded, so no matter what happened—no matter if a terrorist or murderer somehow got access to them—they would never, ever harm a human being.

“No,” Nadia said simply. “That is my second line of programming. My core directive is to do what’s best for you. I ran a lot of scenarios, Watt. And I judged it impossible for you to remain safe as long as that girl was alive.”

“Oh god, oh god,” Watt said slowly. A tingling wind had sprung up, to lash angrily at his face. He felt something stiff and cold on his lashes and realized that he was crying and that the wind had frozen his tears.

It was his fault. No matter what Mariel had done, or might have done, she had still died because of him. Because of an error he’d made when programming a computer at age thirteen.

Watt didn’t have a choice. He turned the boat around and started back toward the dock.

Nadia didn’t ask where they were headed. Maybe she already knew.

LEDA

LEDA STOOD THERE with the rest of them: the heaving, surging cluster of people on the Fullers’ private landing, all trying desperately to find out what was going on.

Though she wasn’t like the rest of them, she thought wildly. They were a jumbled mix of reporters and media, zettas hovering eerily around their shoulders, and a few people Leda actually knew. She saw Risha, Jess, and Ming clustered to one side, making a show of their loud, promiscuous grief.

She didn’t join them. They had abandoned Avery when she needed them most, and Leda wasn’t about to forget it.

She focused on her anger, because it was easier than feeling grief. The anger sharpened her senses, reenergized her, kept her from imagining what could have happened to Avery up there on the thousandth floor.

“What do you think is going on?” asked a woman with frizzy hair and wide, eager eyes. Leda pursed her lips and didn’t answer. This wasn’t fuel for the gossip machine; this was Avery’s life they were talking about.

And yet the gossip kept on churning, each story more outlandish than the last. Avery had burned down the apartment. Avery had run away to elope with her German boyfriend; no, Avery had run away with Atlas, and the German boyfriend had burned down the apartment, threatening to kill them, or himself, or all three.

Worst of all was the rumor that Avery had thrown herself off the roof, just as her friend Eris had done.

Leda tried not to listen, but as the minutes slipped by, people kept filling the space with their bodies and this stupid talk. Telling the same stories over and over, with successively worse endings.

Finally someone emerged from the Fullers’ private elevator: a fire marshal, a silver-haired man with tired eyes and a firm, no-nonsense expression. “Excuse me,” Leda cried out, lunging forward to pluck at his sleeve. “What’s going on up there?”