Petra’s grin was slow and wide. “There wasn’t before, but there is now. We had a talk about testing some spectrascope technology, and they’re interested to add that capability to their search for extraterrestrial life.” She swept her hair off her shoulders dramatically. “Anyway, Sheela agreed to test and run the specs, and voilà.” She shifted her gaze to Roger and her smile was canny. “Leasing an Ombud-patented process to NASA should give us a nice cushion in the budget.”

“Coyotes,” Theo said. “In terms of additional funds. Just want to put that out there.”

“So what did you find?” I asked Petra. We could discuss coyotes later, too.

“More null spots than Black seemed to suggest,” she said. The overhead screen became a satellite image of Chicago with our ward map as an overlay. The wards, Cornerstones, and ley lines were visible, as were thousands of little black dots. It looked like a swarm of gnats.

“Nearly four thousand magical voids detected using this method,” Petra said. “Those are spots in Chicago with an absolute-zero magical signature.”

“Those can’t all be Cornerstones,” I said.

“Oh, definitely not. Like I said, Chicago has a lot of ambient magical energy floating around out there, so most spots in Chicago are going to register some kind of magic. And there could be lots of reasons for spots that show up as absolute zero. Bank vaults. Geological quirks. The remains of the Manhattan Project lab, which sounds fake, but is totally real.”

“That’s so many places,” Theo said. “How does that help us?”

“Well,” Petra said, “it’s a finite number. A limited number of sites is better than all the sites, at least in my mind. But you’re right. We can’t search that many spots in person. So I did one more analysis.”

Another map filled the screen. This time, the gnats had been replaced by a few dozen blue dots spread across town. She looked at us with the smile of a proud parent. “Anyone want to guess how I narrowed it down?”

“Leo’s coffee locations?” I asked, natch.

“No.”

“Starbucks?” Theo asked, and Petra rolled her eyes.

“It is not coffee-related, you addicts.” She lifted her brows, waited. “Since there are no takers, I’ll tell you.” She glanced at me. “You said something at the warehouse that intrigued me.”

I waved a genteel hand. “Carry on.”

“You pointed out that the Cornerstones were voids. But the wards were not.”

“Oooooh,” Roger said, “I got it. These aren’t just voids. They’re voids beside powerful magic.”

“Bingo,” Petra said. “Of those few thousand voids, there are thirty-four that are next to something powerful.” She flipped to another image. This one looked like a weather radar image—a splotch of green with a smaller splotch of red beside it. “Zero magic, high magic. I’m calling them ‘hot spots.’ ”

“You’re a freaking genius,” Theo said.

“Feel free to pass that on to Dr. Anderson,” Petra muttered.

“Thirty-four hot spots—while undeniably genius—is still a lot of ground to cover given our deadline,” Roger said. “We’ve got two days. Can we narrow that down?”