The tech cocked her head at Burke and then went back to work.

“What are you looking for?” Nic finally asked.

“I’m not looking for anything. I’ve already found it.”

“Found what?”

“The source of the NFC signals, at least one of the sources. There’s also one at the opposite end of the wall.”

Nic scratched his head, and Carter said, “What exactly is an NFC signal?”

Burke kept his eyes on his work but explained, “Near Field Communication. It’s a set of communication protocols enabling two devices to establish communication by bringing them within about two inches of each other. NFC operates within the globally available unlicensed radio frequency ISM band of 13.56 MHz on ISO/IEC 18000-3 air interface at rates ranging from 106 to 424 kbit/s.”

“Cleared things right up for me, buddy,” Nic said.

“It’s the same tech you would use to pay for a Starbucks coffee with your cell phone. The odd thing is that when I was examining the vault room at the North Vegas location, I detected some type of highly encrypted NFC within the back corners of the room. And as I suspected, the signal is present here as well.”

Carter walked over and examined the tiled wall more closely. “So the manager’s missing watch is like a key that unlocks a secret door?”

“I don’t think so. More like it lets you access the keyhole. One sec. I think I almost have it.”

Burke tapped on his iPad for a few more moments and something happened. Nic’s hand instinctively went to his holstered sidearm as he heard the small click and whirring of a tile popping out of the wall and folding down into a small access terminal. On its face rested a keypad containing both numbers and letters, a thumbprint scanner, and what Nic guessed to be a retinal scanner.

“That’s why they took out the manager’s eye,” Nic said. “But why not just make him come in here to open it?”

“I thought about that too,” Burke said. “My guess is there’s an additional security checkpoint once you reach the bottom, and so they didn’t want to drag him along. Or maybe they needed the retinal scan to access computers in the lab. Or maybe they’re just really mean people.”

Nic shook his head. “Back up. You lost me. What lab? What are we looking at here?”

Burke smiled. He had everyone’s attention now, including the two techs who had earlier dismissed whatever signal Burke had discovered. “It’s pretty slick really. What’s the problem with having a secure facility that you don’t want anyone to know about?”

Carter, examining the panel, replied, “Security and detection. If the place is guarded, someone obviously knows there is something important there. So you conceal the entrance, leave it unguarded, in plain sight.”

“Yes, but there is a long list of other issues. Equipment going in and out. Personnel entering and exiting. Power consumption. Sure, if you’re just wanting to interrogate a suspect, you can do it in a basement or an abandoned warehouse. But what if you wanted to set up a secured research facility or long-term prisoner holding or hidden safe house? How do you build something like that and keep the entrance secure without anyone ever knowing it’s there?”