Kill Decision(102)

McKinney sat listening to the kids playing soccer for a while. The children laughing—untroubled by the momentous events of the world.

She gestured to the covered object in the center of the table. “What’s in the sack?”

“Something you should see. I didn’t want to alarm you until you were better.”

“I’ve been alarmed ever since I met you.”

“Okay, then . . .” He unfolded the burlap to reveal one of the black weaver-drone quadracopters that had attacked them in Colorado.

A slightly irrational fear gripped her. It was clearly dead—damaged and missing half its rotors. As a scientist, she was angered by irrational fears, so she tamped it down and leaned forward to look at the drone.

The core of it looked mostly intact, although none of the rotors at its four corners was still whole. The spikelike metal feet protruded menacingly, clearly sharpened like metal thorns.

“We managed to reconstruct this one by cannibalizing parts from the two that got into the plane cabin.” He picked up the lightweight device. “It wasn’t difficult. I get the feeling these were meant to be assembled by semiskilled workers. They’re modular, cheap. Mostly dual-use off-the-shelf parts. Circuit boards. Memory chips. Batteries. Optical sensors.”

She extended her hand, and he passed the dead drone to her. McKinney’s curiosity had already bested her anxiety, and she peered into its recesses, rotating it around. The broken propellers flopped around at the ends of wires. Her nose caught the peppery scent she remembered from the Colorado swarm. “There’s that smell again. Like cayenne pepper. I’d like to know the chemical composition.”

Odin nodded. “Mouse knows a few local chemists. Ex-cartel people. I’ll see if he can get it analyzed.”

She kept sniffing and traced it to nozzles next to a row of silvery capsules in the frame. They looked like the nitrous oxide cartridges used for whipped cream or the CO2 propellant in paintball guns. “Four capsules. Like the chemical glands of a weaver. Mixing them in varying proportions to communicate different messages. That would match ant behavior. It’s how they lay down a pheromone matrix.”

“So they were leaving a trail.”

“It’s probably how they incite each other to attack. Each new arrival at a scene reinforces the attack message by spraying more pheromone. But that also means they’d need some way to read each other’s chemical pheromones.”

“Like an electronic nose.”

“Right.” McKinney ran her finger along one of four forward-facing wire antennas that were studded with tiny microchips.

Odin peered closely right next to her.

“Weaver ants—ants in general, actually—have dozens of sensilla on their antennas. They detect all sorts of things, chemical traces, heat, humidity. If these devices are running my weaver model, then they’d respond to numeric pheromonal input values. It’s virtual in my simulations, but here it could be a concentration measurement received from a hardware sensor. Weavers also transmit information to each other by touch, vibration.” She ran her fingers along each antenna, noting half a dozen small nodules.

“They transmit data to each other physically as well?”

McKinney nodded. “It allows them to move information through the swarm separate of the pheromones.”

“And we wouldn’t be able to jam that communication with radio countermeasures either.”

“I suppose that’s true of both the chemical and touch communication. But also, I was wondering how they found us—how they detected we were in the house, and where.”

“I was wondering about that too. These stupid little bots outperformed any system I’ve ever seen. We were wearing cool suits to hide our thermal signature and AD armor to conceal our human shape and faces. That fooled the sniper stations in the hills, but not these bastards. I was thinking maybe they reacted to noise or movement.”

McKinney shook her head. “If they’re using the weaver model I created, they’d focus on organic compound sensors. Ants have receptors in their antennas that help them identify food. Maybe—”

“You’re saying they smelled us?”

“Or tasted us.” She sighed. “I know it sounds silly, but that’s part of what weavers do when they swarm. They detect food sources by trace chemicals—in much the same way as they read each other’s pheromone messages.”

Odin seemed to be contemplating something. “It doesn’t sound silly at all, in fact.”

“What?”

“There’s a technology—well known in counterterrorism work, used by customs and Homeland Security. It’s called ‘C-Scout MAS.’ We used it while hunting for high-value insurgent targets.”