Alex palmed the gun in his holster hidden under his jacket. He was sure Tilden had noticed, but the guard hadn’t stopped him from entering the building, and he appreciated that the man had common sense enough to allow Alex to protect Mackenzie.

His muscles tensed as the elevator stopped. It only had to go one floor, but that seemed to take an eternity—maybe the lower level was deeper than the elevator indicated.

“What can we expect on the lower level? Please tell me no one is working down there.”

Mackenzie shook her head. “We didn’t see other cars in the parking lot, but I also looked at those cameras before looping them. I didn’t see anyone.”

He braced himself for what lay on the other side of the elevator door. The elevator dinged, and the doors whooshed open to reveal the dark lower level. Dark except for a few lights—white, blue, and some red—spilling from racks of servers behind glass walls.

Mackenzie exited the elevator and motion-detector lights popped on. Alex stepped out too but held her back.

“I’ll go first.”

“Make it quick,” she said. “We have seven minutes before the cameras flip back.”

He held his gun at his side. They passed the server room and found cubicles with desks and monitors, and beyond that, another glass wall.

No lights on behind it.

Mackenzie rushed forward and opened up the door to the server room, then slipped inside. He followed behind her. She walked through the tall racks as if searching for one in particular.

“What are we looking for?”

“You know the system is air-gapped. There’s no network interface. No Wi-Fi or Bluetooth. Nothing that could be used to send the data outside the machine.”

“So how will you get in?” He had an idea but enjoyed watching her in her element.

“A method called Air-Fi. Think a MacGyver type of hack. I’ll create an Air-Fi covert channel, via encryption keys and credentials, to start exfiltrating the data. These servers emit electromagnetic radiation, and anything with a Wi-Fi interface will pick up the exfiltrated data. Basically, Air-Fi mimics Wi-Fi. You just have to know how to plug into it. Once I’m in, I’ll inject code to allow me to encode and read signals—exfiltration. Find the malware and deploy anti-malware code. It’s slower than actual Wi-Fi but hard to detect.”

“I suspect there’s much more to it.”

“I don’t have time to explain.”

He admired her skills. Her brain. Her smile and those bright eyes that flashed at him. She dug in her bag and pulled out a cell.

Alex arched a brow. “You told Tilden you left your cell in the car.”