FROM HIS UNEXPECTED vantage point on the East River, Watt was one of the first people to see the thousandth floor catch fire.
It was striking, really: the brightness of the flames curling above the Tower, an elegant orange-red brushstroke. Opalescent gray thunderheads coalesced around the rain-blimps, hanging in that low winter way that portended the first dusting of snow. There was something magical about it, even now that the whole thing was engineered: the delicate crystalline miracle reduced to a chemical reaction, the mating of hydrosulphates and carbon.
The magic was in the air, in the way people reacted. New Yorkers loved the first snowfall of the year—they wore hats inside the Tower and smiled at strangers and started humming holiday music. Watt remembered hearing that at MIT, the freshmen class went streaking on the evening of the first snowfall. Not that he would ever get to see it.
He wondered how Leda was doing. He’d tried pinging her a few times—okay, maybe a lot of times—since she left him at the inauguration ball on Saturday night, but she had steadfastly ignored him. He understood that she had a lot of things to work through; especially now, after what her best friend had done. Watt had plenty to think about, himself.
This morning he had turned off Nadia to ponder it all in silence, in the privacy of his own mind. And he’d rented a boat for the first time in his life. Or rather, borrowed one without asking.
The dock was closed when he got there: It was far too early, especially on a scheduled weather day. WARNING: PRECIPITATION ALERT, the screen had flashed, refusing to let him rent anything, but Watt wasn’t about to let that stop him. Even without Nadia, it was the work of a few moments for him to hack the rental shop’s operational computer.
He settled on a blue quadro-blade, one of the small speedboats that skimmed above the choppy surface of the waves, lifted on hydrofoil wings. He typed his destination into the boat’s GPS and leaned back as it darted him upriver, like a bug zipping over the water.
Watt saw the infrastructure along the east side of the Tower rip past him without actually registering it. He had an idea too unspeakable to even put into words, and he needed to step back from it—to let himself view it out of the corner of his eye, in his peripheral vision—before he could bear to face it head-on.
Right on schedule, the snow began to fall. It stung Watt into alertness as he sped along. A BrightRain hovercover floated out of the back of the boat; Watt considered putting it away but decided it wasn’t worth the bother. The hovercover floated softly over his head and began to emit a soft yellow glow. Its conductive membrane was converting the kinetic energy of the snowfall into electricity.
Watt pulled up along the spot where Mariel had drowned, near a dock on the East River. He killed the motor. The boat’s foils retracted back into its sides, lowering the boat softly into the water, to be rocked back and forth by the waves.
He stared at the pier. Along this stretch of it, for several hundred meters, extended a multiuse dock—the kind of place you could recharge autocars or pull up a boat. Half the dock was covered by a roof, while the other half was open to the elements, lined with sunplates. A small shed in the corner probably housed spare equipment, maybe a human employee during working hours.
Watt tried to imagine Leda, high and vengeful, logging on to the feeds and figuring out where Mariel was. Following her here from José’s party, then pushing her violently into the water. Except, how would Leda have known that Mariel was going to walk home instead of taking the monorail? Or was Leda reckless and high enough to act on impulse, to follow Mariel not knowing where she was headed? Did Leda know that it was going to rain that night or that Mariel couldn’t swim?
He couldn’t shake the feeling that Leda wasn’t capable of such a thing, no matter how desperate or afraid she’d felt.
Watt’s eyes drank in every detail of the charging station. He watched the autocars dart in and out, watched a few empty boats rock listlessly at the docks. Hulking transport bots rolled back and forth on their programmed routes, their wheels heavy on the pavement.
The idea in Watt’s mind became more substantial, until finally he could ignore it no longer. Because pushing Mariel into the water on a dark and stormy night—the perfect conditions to make something look like an accident, at least at first glance—didn’t sound like Leda. It was too neat, too rational, too much the perfect crime.
Watt knew who might have done it.
“Quant on,” he muttered, and felt the familiar textured deepening of his own awareness as Nadia stirred to life. He waited for Nadia to ask what they were doing out here. When she said nothing, his certainty began to calcify. He felt an unfamiliar urge to cry.
“Nadia. Did you kill Mariel?”
“Yes,” she answered, with startling simplicity.
“Why?” he cried out, the wind biting at his words.
“I did it for you, Watt. Mariel knew too much. She was a liability.”
The morning seemed to condense around him, the snowflakes vibrating in midair. Watt felt an anguished swoop in his gut and closed his eyes.
He could have solved this whole mystery months ago if he had simply thought of asking Nadia. She had no choice but to tell him the truth. She was able to withhold information from him—she had to; if Watt’s brain tried to hold everything she did, it would literally break down and die. He had built her with the ability to keep secrets from him, because there was no other way to build her.
But Nadia couldn’t lie to him, not when he asked her a direct question. He had just never thought to ask this one, until now.
“You had been tracking Mariel’s movements since Dubai, hadn’t you?” he asked, utterly aghast. But he needed to understand. “Just waiting for the right moment, for her to put herself in a vulnerable position. And then she walked home alone, in the dark, and you realized it was the perfect chance to kill her and make it look like an accident. So you hacked one of those big transport bots and made it knock her into the water,” he guessed.
“Yes,” Nadia told him.
“You were afraid she might send me to prison, and so you killed her?”
“I killed her because if she stayed alive, there was more than a ninety-five percent chance that you would end up incarcerated, and more than a thirty percent chance that she would try to kill you! I did the calculations over and over, Watt. Every outcome ended up with you in prison, or worse. Except this one. The only reason Mariel didn’t hurt you is because I hurt her first.”
“And that’s supposed to make me feel better?”
“It’s supposed to make you feel grateful, yes. You’re still alive, and free. Honestly,” Nadia added, “I’m surprised you’re feeling so much guilt, Watt. She left Leda to die, and she was going to hurt you—”
“That doesn’t make you god, to deliver some kind of judgment on her!”
The snow was swirling in soft flakes to hit the river. Each time one of the flakes collided with the surface, it melted almost instantly, dissolving into the water like a tiny frozen teardrop.
Nadia didn’t even seem sorry. But of course she couldn’t be sorry, Watt corrected himself, she couldn’t feel anything, because she was a machine; and no matter how many clever jokes she made or ideas she seemed to generate, no matter how many times she knew exactly what to say when he was upset, she was still a machine, and there was no way for him to have programmed her with that elusive human trait called empathy.
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.