Skip to content
Answering Your Questions About Reactor: Right here.
Sign up for our weekly newsletter. Everything in one handy email.

Read an Excerpt from S.L. Huang’s Null Set


Read an Excerpt from S.L. Huang’s Null Set

Home / Read an Excerpt from S.L. Huang’s Null Set
Excerpts Excerpts

Read an Excerpt from S.L. Huang’s Null Set

Book 2 in the Cas Russell series. Math-genius mercenary Cas Russell has decided to Fight Crime(tm). After all, with her extraordinary mathematical ability, she can neuter bombs or out-shoot an…


Published on June 5, 2019


Math-genius mercenary Cas Russell has decided to Fight Crime(tm). After all, with her extraordinary mathematical ability, she can neuter bombs or out-shoot an army. And the recent outbreak of violence in the world’s cities is Cas’s fault—she’s the one who crushed the organization of telepaths keeping the world’s worst offenders under control.

But Cas’s own power also has a history, one she can’t remember—or control. One that’s creeping into her mind and fracturing her sanity…just when she’s gotten herself on the hit list of every crime lord on the West Coast. And her best, only, sociopathic friend. Cas won’t be able to save the world. She might not even be able to save herself.

S.L. Huang’s Null Set is the second book in the Cas Russell series—available July 9th from Tor Books Get started here with the first two chapters, and continue with chapter three below!




Arthur came with me to the Hole, probably because he was afraid I would chicken out.

The Hole was technically Checker’s converted garage-turned-hacker cave, but at this time of morning and after the night we’d all had, it was marginally more likely he was in bed in his house rather than online. We tromped up the ramp onto his porch, and I pounded on his door loudly enough that I probably woke several of his neighbors. When he didn’t answer right away, I pounded again.

It took six and a half minutes, but finally we heard the deadbolt slide back and a skinny white guy with a goatee swung the door open. He blinked up from his wheelchair at us in the morning light as he shoved his glasses onto his face; his hair was tousled with sleep and he wore pajama pants and a T-shirt with a picture of the Milky Way on it and the words, “You are here.”

“Cas,” he said, after a good eight seconds. I couldn’t tell if he was glad to see me or not.

“Hey,” I said.

He couldn’t seem to think what to say back. I crossed my arms tightly and looked at the worn floorboards of the porch, trying to ignore how long I’d been refusing to talk to him.

“Can we come in?” said Arthur after another highly awkward fifteen seconds.

“Okay. Right,” said Checker, and moved back from the door, pulling it open the rest of the way for us.

We followed him into his living room. Arthur sat back on the couch; I remained standing, shifting from foot to foot.

“So what are you doing here?” said Checker.

“Cas has something to say to you,” Arthur answered.

“Yeah,” I said. “I’m having… I’m having a problem. I think I…”

“You got something to say before that,” interrupted Arthur firmly.

“I do?”

“You do.”


Arthur just kept looking at me meaningfully. The awkwardness ratcheted up a couple more notches.

“Oh, for the love of Tesla,” said Checker. “Arthur, stop it. He’s trying to get you to apologize,” he said to me.


“She doesn’t have to. Cas, I forgive you for being such an asshole to me, okay? Done. Now, what’s going on?”

Buy the Book

Null Set
Null Set

Null Set

Some of the tension in the room bled out. I moved over to sit next to Arthur on the couch. “The memory thing,” I said. “I think… it turns out it might be an issue.” I braced myself for a sarcastic I told you so.

“What happened?” Checker said instead. He wasn’t a person I would have generally characterized as “gentle”—brilliant, cheerful, voracious, slightly mad, but not gentle—but he sounded that way now. As if he wanted to protect me.

Which was ridiculous, of course, since I could have kicked his ass and Arthur’s together without breathing hard, but I was suddenly, incongruously, reminded of how much I missed spending time with him.

I cleared my throat and tried to focus. “I don’t know if looking into it would make things worse or not,” I ground out. “But I feel like… I don’t know.”

Checker digested that. “I’m still willing to help you track down your… whatever your previous life was,” he said. “Maybe understanding more would help? We could take it slow.”

“I don’t know,” I said again, more belligerently. “I still don’t think I should.” I’d told myself not to… but what was the alternative? Do nothing?

“She’s started getting flashes,” Arthur said. “Since Dawna.”

Checker’s eyes got wide. “Oh. Crap.”

“Since then, but… worse lately.” I rubbed at my face. “She broke something. In my mind. And then you being all ‘Cas, you have to find out who you were,’ like picking a goddamn scab—”

“I’m sorry,” blurted Checker.

“Yeah, well, you should be.”

Arthur made a small sound beside me.

Checker took a breath. “All right, I’m asking you. What would you like to do?”

Like I had an answer for that. I opened my mouth. Shut it. Opened it again. “I want to stomp out this crime wave.”

“What?” Checker said.

“Dawna’s not the only one with a superpower. If she could do it, I should be able to, too.”

He snorted a laugh. “Only you would decide to fight crime because you don’t want to be shown up.” Then he looked uncertain, as if he wasn’t sure if it was okay to take the mickey with me again yet.

I pretended not to notice. “It’s only a matter of time before LA’s being run by warring organized crime rings. We’re not going to let that happen. There’s got to be a way to cut them down.”

But Dawna was a psychic. How to leverage mathematics to do it instead? What was a supernatural math ability good for? I’d need to merge it with some sort of technology.… “Pilar,” I said aloud. “I need to talk to Pilar.”

“Russell, we were talking about you,” Arthur murmured.


“How about this,” Checker said. “If you really feel like you don’t want to know… why don’t I take the lead for you? If you’re comfortable. I’ll ask you questions, and try to find out where you came from, and if I find a good reason not to tell you what I find, I won’t, but at least we’ll know if there’s anything, anything dangerous, or if there’s any way we can help you.…”

Despite having been the one to come here, I still felt inclined to snap at his suggestion. But then I’d have to answer his question about what I did want.

Putting my history in Checker’s hands… it felt vulnerable, too trusting. Even though I’d been trying to make a conscious choice to trust more, to force myself to believe in the people I now called friends… this was a hell of a lot to ask.

Besides, Dawna had been the one to tell me to remember. The last thing I should be doing was listening to her. But Arthur was right: whatever chaos she had pried open inside my head, ignoring it was no longer an option.

The only choice remaining was to change a variable.

I hunched into the couch, curling around myself. “I reserve the right to put a stop to this at any time.”

“Unless—” started Checker.

“No. I say stop, you stop.”

He waited until I looked up, then met my gaze seriously. “Okay. It’s a deal.”

I was tempted to stop right then, tell them we weren’t going anywhere with this. In fact, something in me was already screaming about what a bad decision this was, some intuition lambasting me that this was wrong, wrong, wrong—

I forced myself to nod.

Checker and Arthur exchanged a glance. “All right,” Checker said. He reached over to pick up a tablet off an end table. “We’ll go slow, okay? What’s the first thing you remember?”

“I can’t answer that,” I said. “My memories aren’t a well-ordered set.”

“You mean you don’t have a definite earliest memory?”

“No.” I was staring at the floor now.

“Can you remember anything from before you lived in Los Angeles?”

“No.” That wasn’t strictly true. “I only have— When I think of being a kid, I see… all people who look like me. Brown skin, black hair. Lights. Bright colors. And then some other image—a classroom, I think. That’s it.”

“Didn’t think it was likely you’re from the US,” Arthur said. “The way you talk. You mix your dialect.”

“I don’t have an accent,” I objected.

“Well, you do—General American, or close to it. But I’m not talking about an accent. Your vocabulary’s a mix.”

Checker frowned. “Yeah, I think I noticed that, too; I just didn’t think anything of it because I watch so much British television—but you’re right, Arthur. You use words like ‘mobile’ and ‘lift,’” he added to me.

“Flat,” said Arthur. “Washroom. Ground floor—”

“Okay!” I cut in, feeling uncomfortably scrutinized.

“But the American versions, too,” continued Arthur. “Like you got extra synonyms or something.”

“Enough. I’m done for the day.” I was already sick of this. I stood up and pointed at Checker. “I’m going to go get drunk and pass out. You—when I wake up I want a statistical analysis of the recent increase in crime.”

“Way to be specific. What kind of statistical analysis, pray tell?”

“Any numbers you can get your hands on. Get me the data, and run your stochastic programs.”

“You realize that it’s not as easy as—”

“I have every faith in you,” I said, and stalked out the door without looking back.

I didn’t wait for Arthur to drive me home. I stole a car off the next street over instead. The shadows yawed and writhed at me as if a million eyes drilled into my back, but I paid no attention.


I didn’t sleep well.

As usual lately, my dreams were a confusing mass of colors and images, realities I thought I might be able to understand if I only had a second to look closer. I saw a dark boy with curly hair and a thin black girl. I saw mountains, and some type of aircraft, and a desert, and a jungle, and I screamed and I died.

When I woke up, tangled in blankets and empty liquor bottles, I didn’t feel rested. Unfortunately, I did feel sober, and I couldn’t indulge in more alcohol because I’d assigned myself this stupid crime-fighting job. At least working kept my brain busy enough that it staved off the need to self-medicate.

I fought traffic down to Arthur’s private investigations office, which was a clean and respectable hole-in-the-wall in a terrible part of town. I knew for a fact that Arthur and Checker could afford a better location for the business; Checker had let slip one night that he wished Arthur would move to Beverly Hills but the idiot insisted he preferred “fighting for people who needed it”—whatever that meant. Checker never came into the office himself, doing his information-gathering via telecommute, so Arthur had veto power on the location.

Today, however, something itched at my awareness as soon as I got out of the car. I stood on the street for a minute and let my surroundings seep into my senses, the inputs dropping through functions into outputs, cause and effect. Everything fell within error margins, mundane and safe.

What the hell?

I took one last look around before dismissing whatever vibe I’d had as a subliminal outlier and climbing the outside stairs to the heavy door stenciled with “Arthur Tresting, Private Investigations.” I pushed it open into a pleasant, professional office.

Arthur had renovated and expanded since the place had gotten shot up. Now the door opened into a bright reception area with Pilar’s station in it. I expected to find her at her desk like usual, but instead the small front room had been taken over by two young teenagers who were brandishing their phones at each other like swords.

“Ah hahahaha, I got you!” the girl cried, and then did an honest-to-goodness somersault to come up on the other side of Pilar’s desk.

“Ya got me!” the boy yelled dramatically, collapsing to the floor. A loud series of clangs sounded from his phone speaker as he let his hand fall.

“What the hell is this?” I wasn’t annoyed, just puzzled. I didn’t really understand kids, but I generally liked them more than adults, and if Arthur wanted to let them run roughshod over his office having fake sword fights, that was his business.

The kids’ heads whipped over to me and they scrambled up. The girl looked defiant, the boy scared.

“Pilar said—” started the boy, his eyes darting to his partner in crime, but at that moment Pilar herself came out of Arthur’s inner office, toting a stack of files. She wore a bright ruffled blouse and looked as chipper as if she hadn’t been up half the night running dispatch for us.

“Cas! Hi!” She gave me a huge smile—and a genuine one, as far as I could tell. Almost as short as I was but quite a bit heavier, Pilar was charming and cheerful and one of those people who basically personified the word “cute.” Arthur and Checker had snatched her up after meeting her on a case, and she was one hell of an office manager.

And a good shot. Arthur was still mad I’d taught her firearms.

“I see you met Katrina and Justin,” Pilar continued, waving at the teens. “Guys, this is Cas. She’s been helping Arthur fight back against Pourdry.”

I blinked. Why would these two know about— But they both shrank back upon hearing the name, and Katrina spit a blue stream of cussing that beat even my usual discourse.

And then I saw what I hadn’t noticed right away. Despite their smartphones, these kids weren’t out of a cushy suburban home. Katrina’s hair was tangled and lanky, and needle scars crisscrossed her forearms under a profusion of cheap bangles. Justin’s clothes were cleaner than hers, but threadbare at the seams, and his sneakers had been worn flat.

“They aren’t some of the kids we pulled out last night, are they?” I said.

“We can hear you, you know,” Katrina spoke up rebelliously. “You can talk to us directly.”

“No,” Pilar answered me. “But they and their friends had some trouble with some of Pourdry’s guys a little while ago. Arthur’s been helping them out.”

Katrina thrust her head up and stuck a hand on her hip. “Think of us like clients.”

“Sure,” I said. “Tiny clients.”

“Who’re you calling tiny?”

“Okay, okay, no fistfights,” Pilar said, hurrying to shepherd Katrina and Justin to the visitors’ chairs. She also shot me an exasperated look, though I didn’t know what she thought I had done. “Cas, Arthur’s not in yet. D’you want to come back later?”

“Actually, I came to see you.” I swung over and sat down on the edge of her desk. “Your ex-employer. Arkacite Technologies.”

“You used to work for Arkacite?” broke in the talkative Katrina. “Whoa, man! They, like, made my phone.” She waved it at us.

“And now they’re bankrupt and dead,” Pilar said. She still sounded cheerful, but her smile was starting to strain a bit. “What about them?”

I searched my memory. Pilar regularly brought up weird tech she’d seen while working there, from biotech to AI software. Technologies for people in comas that could literally read minds, or gadgets that could help law enforcement…

“I’m looking for information on a specific kind of technology,” I said. “But I’m not sure what yet. Start with anything you knew about that was being tested for police or military applications.”

“Cas, I’m happy to talk to you about this, but I’m really very busy right now—”

“Aw, man, Velasquez,” Justin chimed in. “You worked for the Five-Oh? I thought you was one of us.”

Pilar put down her files and heaved a sigh. “If it makes you feel any better, Justin—most of it didn’t work. There was a thingummy for police to remote-disable cars, but they could never get it functional. Or some frequency generation stuff to break up mob violence, and ditto. Most of the stuff they did manage to make was for the military—they did get some really sleek robots off the ground for sensing and then disabling IEDs, and lots of spy stuff that was actually pretty cool, like little cameras that would attach themselves to bugs—you’d like it—”

“Go back,” I said. “What was the frequency generation thing? You mean something that would calm people down? Make them less aggressive?”

“Hey, no one’s making me less aggressive,” Katrina called. “It’s like that white woman always said. We women gotta lean in.” She made a gesture with both fists that looked vaguely obscene. I wouldn’t have pegged Katrina herself as not being white, but with her dark hair and olive skin, I guessed she was probably an ethnic mix. She leaned back in her chair, crossing her arms over a tank top that read, “I’m not a bitch, I just act like one.”

“I like her,” I said to Pilar.

“Lady, I told you, I can hear you,” Katrina said.

I gave her a grin and tapped the middle of Pilar’s desk, on top of her files. “Frequency generation?”

“All right, all right.” Pilar put aside her other work and turned fully to me. “This is actually something important? You’re not just making conversation?”

“Since when do I ever make conversation?”

“Yes, very true. I guess we’d better go back into Arthur’s office, then.” She stood up, led me back through the inner door, and shut it over Katrina’s good-natured objections at our unfairness in taking the conversation elsewhere. Pilar gave me a wry smile and took Arthur’s chair while I dropped into one of the client seats.

“Now what is it you need?” she asked.

“This frequency generation tech. You were saying they wanted to use it to stamp out aggression?”

“Not quite.” She cocked her head to the side and thought for a minute. “I mean, I suppose that was the result they were going for, sure. But what it really did was break people out of, um—‘deindividuation,’ that was what they called it. Which in practice meant—”

“They were looking to disrupt mob mentalities,” I guessed.

She nodded. “Exactly, that was a big part of it. The Signet Devices— that was the project code name—they emitted a frequency or something that stops the brain feeling… you know how people can get in crowds? They lose control, they get all overwhelmed and sucked into the group… ‘crowd psychology,’ that’s another thing they kept saying. How people feel swallowed into the masses and lose their sense of personal responsibility. They found a frequency or something that stops that from happening. The idea being that when they get swept up in those situations, people do all sorts of awful things they wouldn’t ordinarily if they’d just been able to think about it.”

I thought about the riots LA had been suffering. A lot of people who weren’t ordinarily violent, escalating into layer upon layer of savage destruction.… From what Pilar was saying, the Signet Devices could stop such chaos before it ever sparked.

These things might be able to calm war zones. Or take down cults. Or, heck, even undercut the power of schoolyard bullies.

“It was something the police and military were all sorts of interested in,” Pilar continued. “Really interested. Like, Arkacite had a bajillion meetings with important government people through the whole fiasco.”

“So why isn’t it out there?” This sounded like exactly what I wanted. But she’d just called the project a fiasco… “What went wrong?”

“They couldn’t calibrate it right,” answered Pilar. “No matter how much money the Defense Department piled in. It turns out people’s brains were real sensitive to it. Either it was too low to work, or too high, and—well, then it made the test subjects too individual, made ’em distrust each other and start fighting because of that, instead of mobbing together. So the point was to stamp out aggression, and it ended up causing aggression for a different reason. And there was a sweet spot where it worked, but they could never maintain it reliably, and they especially couldn’t do it evenly over a large area.”

Hmm. “How easy would it be to get more specs on these things?”

I expected Pilar to say I’d need to ask for Checker’s help, but instead she grinned and started logging onto Arthur’s computer. “I’m betting we already have some of it. At least the testing data. Remember how I ended up working here? Checker pulled everything out of Arkacite that wasn’t behind a military firewall, even if it wasn’t relevant at the time, and he never throws any data away when he hacks a place.”

Of course. The very case when Checker had recruited Pilar to work for them. Fabulous.

She started typing, her eyes scanning down the screen. “Wow, yeah, there’s a lot. Like… everything. This is going to take me a while to sort through, but I can send you whatever there is on the Signet Devices. What do you need it all for?”

“Calibration’s just math,” I said.

“Wait, you want to build one?” Her voice rose into a squeak.

“No,” I answered. “I want to build a lot of them.”

“What for?”

“The crime in the city lately. I’m looking for a way to axe it, and this sounds like more than a good start.” The possibilities kept expanding in my head. Combating deindividuation would potentially be a sweeping blow against gangs and organized crime, at the very least. I thought of Pourdry’s goons and their blind loyalty and was angry all over again. Devices like these might not be able to stop someone like Pourdry himself, but if they gutted his organization, how powerful would he be then? These things might keep all the big criminal rackets from getting out of hand. “Let’s see how brave these assholes are without their armies to hide behind.”

“You mean you want to put these things around LA?” Pilar’s face stretched itself into a bizarre combination of incredulity and horror. “Cas, don’t take this the wrong way, but that is a terrible idea!”

“Why? I’m not going to do it unless I can get the calibration right, which I bet I can.”

“They barely did any human testing!” she protested. “I don’t even know if it’s something people could take long-term. You could make things way worse—”

“And I could make ’em way better,” I said.

She leaned away from me, shaking her head over and over. “It’s too risky. This is so dangerous. You’re talking about—”

“This could save a lot of lives.”

“I don’t know,” she said. “I want to make LA safer, too, I do, I do, more than anyone. But if this went wrong—think how bad it could go. If you didn’t get it right, people would start tearing each other apart. Normal people. I saw the test results.”

I crossed my arms. “Does that mean you’re not going to give me the files?”

Pilar wavered. “I mean… you do seem to do the impossible on a regular basis. Checker and I have conversations about it, you know. Did you really lasso the wing of a fighter jet one time and—”

Not technically, and certainly not how she was describing it. “I’m good at math,” I interrupted. “That’s all.”

“That’s what you always say! If this were anyone else asking, and I mean anyone else…” She pursed her lips and thought for a moment. “Promise you’re not going to do anything unless you’re sure it’s going to work?”

“Sure. I can promise that.”

She looked down at the desk for a minute. “I’ve got a lot of family here, you know.”

“I know,” I said, confused by the non sequitur. Pilar mentioned her family a lot.

“One of my cousins joined a gang a couple months ago,” she said. “My aunt is devastated. There was no reason, you know? He’s a good kid, good family—and my baby brother’s still in high school, and you know what an LA public school is like. It was a jungle when I went through and now…” She trailed off and cleared her throat. “My mom tells me he comes home with black eyes sometimes. From high school. Can you believe it? It’s not fair. My folks don’t even live in a bad part of town.”

As much as Pilar talked about her family, I tended to forget they actually existed as people. But hey, if they were going to help my cause, I was okay with that. “That’s why I want to do this.”

“I know,” she said, the earnest trust in her voice assigning me more goodwill than I probably deserved. She flapped a hand despondently toward the outer office. “And then you look at people like Katrina and Justin… All they want is a chance, you know? And everything’s against them, all these jerks who just—who want to tear everything down so nobody gets that chance.”

“Yeah,” I said. “Exactly.”

“Okay. All right. All right, I’ll send you whatever I can.”

I felt pretty satisfied as I walked out, enough to be good-humored about Katrina flicking what I was pretty sure were spitballs in my direction as I passed. I flipped up the back of my hand with the right moment of inertia around the pivot point of my wrist, and Newton’s third law bopped them back to hit her in the face. She squawked.

I smiled to myself and stepped out the door.

The pleasant feeling lasted until the sole of my boot hit the sidewalk below—then spooled abruptly away, everything around me jarring, wrong. The sensation of being watched tugged hard at the hairs on the back of my neck.

My hand went to the Colt in my belt, and I glanced back up at Arthur’s office, then around the street. The sidewalk was empty save for one pedestrian, a dark-haired man who shuffled by without taking any notice of me.

The feeling that someone was following still crept up around me, throttling.

What the hell. I didn’t get feelings. I saw quantifiable data that translated into probabilities. I tried to push it away, to tamp it down, but instead it smothered me, stuffed me in darkness, and I saw one of the people from my dreams.

“You’re dead,” he said to me, his face blurred in the throes of either hallucination or memory. “You’re dead. This is only borrowed time.”

Excerpted from Null Set, copyright © 2019 by S.L. Huang.

About the Author

S.L. Huang


S.L. Huang is a Hugo-winning and Amazon-bestselling author who justifies an MIT degree by using it to write eccentric mathematical superhero fiction. The author of the Cas Russell novels from Tor Books as well as the new fantasies Burning Roses and The Water Outlaws, Huang is also a short fiction writer, with stories in Analog, F&SF, Clarkesworld, Nature, and numerous best-of anthologies. When not writing, Huang is a Hollywood stunt performer and firearms expert. Follow S.L. Huang online at   Photo by Chris Massa.
Learn More About S.L.
Notify of
Newest Most Voted
Inline Feedbacks
View all comments