Root of Unity by SL Huang

Arthur.
    He cleared his throat. “The cops just arrived. And bomb squad.”
    “Good,” said Arthur. “What else have you got for us?”
    “You don’t want to talk about the fact that we just saw street cam footage of you two almost being blown to kingdom come? These people are—”
    “We tracked down Professor Halliday’s NSA friend,” cut in Pilar’s voice, as if she could sense Arthur’s growing impatience. “His name’s Dr. Xiaohu Zhang. He’s got a PhD from Berkeley and all the good creds; I think he and Professor Halliday know each other all the way back from then. And he’s been working as a mathematician for the NSA for almost twenty years. As far as we can tell, he’s a good guy. There’s nothing irregular in his bank accounts, he has a wife and three kids, he volunteers planting trees and coaching Little League…pretty much your typical all-American dad.”
    “Who happens to work for a government spy organization that has far too much power and far too little oversight,” put in Checker grumpily.
    “What I’m trying to say is, we don’t think he’s involved,” said Pilar. “Arthur, if you want to—I think this could be a guy you could go to for help.”
    I grimaced. “Even if Zhang’s okay, he’s not going to be the one who calls the shots here. His bosses are going to take it out of his hands.”
    “May I point out that you already called in the police?” said Checker. “The NSA is going to be involved sooner or later, and I remind you that we probably want them involved—and without the delay of the local cops kicking it up to them. They’re going to have a hell of a lot more resources for finding Professor Sonya than the Pasadena PD will, and plus, remember the whole possible-economic-apocalypse? The proof was stolen before we ever made it on the scene, and there’s no putting that genie back in the bottle.”
    Arthur exhaled sharply. “Sonya’s safety is my only concern right now—but you’re right, rather she be in trouble with the Feds than hurt.”
    “If you’re ever coming to rescue me, don’t make those your priorities,” I said.
    Arthur threw me a black look. “Here’s what we’ll do. I can’t give up no chance on this. Where’s Zhang now? At work?”
    “No, he took the day off today,” said Pilar. “He’s chaperoning his daughter’s class trip to the tar pits.”
    “Even better. Pilar, you go talk to him.”
    She hesitated. “Okay.”
    “You’ll be fine,” said Arthur. “Just be honest about what’s going on. Checker’s right, we got to go in whole hog here, ain’t no point in dancing around no more. You can even tell him I’m on my way but I sent you first. Leave Russell and Checker out of it—I want ’em free to keep at this thing without the government coming knocking, so tell ’em it’s just me. But don’t worry about hiding nothing else, got it?”
    “Got it,” said Pilar.
    “I’m going to keep looking into this a little longer before breaking off and joining with the Feds. Checker, you got anything else?”
    “The SUV that tried to kill you has hit police impound,” said Checker.
    Arthur nodded. “I’ll pull some strings, get in to take a look.”
    “While you do that, can I have Cas? I could use her help for the van tracking. Extrapolation is sort of your thing,” Checker added to me.
    “Done,” said Arthur. I wondered if I heard a hint of relief in his voice that he wasn’t going to have to wrangle my differences in method for a while, and then wondered if I was being paranoid. He’d asked me in on this, hadn’t he?
    As a last resort. Because nobody else knew enough math. Not because he wanted me on the job with him.
    “You’re sending Pilar into the lion’s den. You realize that, don’t you?” The accusation spewed out harshly as Arthur hung up. It wasn’t what I wanted to say. “If the NSA thinks she’s involved, or just thinks she’s hiding anything, they could bury her.”
    He scrubbed a hand across his