“The force-shield takes significant power. You can run the cloak for about ten hours without a recharge, but only five minutes for the shield. And they run off the same power source, so those times are in total.”

“Ah. So if I’ve been invisible for five hours, I will only have two and a half minutes of shield available.”

“More or less. But essentially correct. I should also mention that the shield creates some resistance to movement. You will feel like you are walking through water. Running will be impossible.”

“Okay. Well, here goes.”

I pressed the left button, and Nat screamed and jumped back, then slapped both hands over her mouth. “Mmpf,” she said, her eyes wide with fear.

I held up my hand to examine it. “Oh, that’s just … disgusting.”

The effect was certainly incomplete. My clothes were invisible, which in and of itself should normally be traumatic enough. But in addition, my skin was almost invisible, and things became progressively more visible farther in, until my skeleton was maybe fifty percent there. I reached down and pressed the button again to deactivate the device. “I’m going to call that a fail.”

“Oh, I disagree,” Sheldon said. “That was comedy gold. Natalie’s face—I admit I’m not an expert at reading human expressions, but the mmpf really sold it.”

Nat gritted her teeth. “Asshole.”

“Not part of the design, sorry.”

I had to laugh. “Can you fix it?”

“I can try. One moment … All right, try now.”

“Wait, what? You didn’t do anything,” Nat said.

“I adjusted the device, Natalie. Everything is software. Even with human technology, and I use that term loosely, the hardware only provides the basic functionality. Software provides most of the features and operating parameters.”

I nodded in agreement. “He’s right. My 360 camera, for instance, has had several features added to it just by downloading new firmware from their website. The camera itself hasn’t changed.”

“Huh. Okay, I’ll take your word for it. So press the button, and let’s see what happens.”

I pressed the left button again.

Nat’s eyes again went wide, but this time without the accompanying fear. “My God, Jack, it works. You’re invisible.”

I smiled to myself and stepped around her to her left. To my consternation, she turned her head to follow me.

“I thought I was invisible.” I held up my arm to confirm. Yep. Not there.

“But you’re not inaudible, dum-dum. Try not dragging your feet.”

“Oh.” I pushed the left button and watched as my arm reappeared. “Good point, though. Being invisible doesn’t help with noise, or walking through tall grass, or fog, or rain … ”

“Yeah,” Nat said. “We really have to pick our times.”

“Also, leave your phone behind when playing spy,” Sheldon said. “The radio transmissions are easily detected.”

“I changed my mind.” I removed the belt and held it out to Nat. “You do it.”