“Why don’t we give it a dry run? See if I can reach up and push the cover aside a bit, at least.” And let in fresh air to mitigate the lethal CO2 levels that would begin building up fast with two people breathing the air—and expelling carbon dioxide—if the cistern was sealed tight.

“I’m game—but you’re going to have to walk me through how to do this.”

“It’s not that hard.” Cate pushed herself to her feet, trying to ignore the twinge in her ribs. They were healing, but the process was slow and this maneuver wasn’t going to help them.

Especially if she fell.

But thinking too much about that would spook her—and what choice did they have?

Kayla stood too.

“Here’s how it works.” Cate pulled off her boots and shed her excess garments, positioned Kayla under the opening in the center of the cistern, and dug deep in her memory for the how-to of the acrobatic stunt. “I’m going to stand behind you. You spread your legs apart, kind of squat down, and lift your hands shoulder height. Try it.”

Kayla complied, wincing as she raised her wounded arm. “Ouch.”

Cate caught her lower lip between her teeth. The maneuver could be dangerous even for able-bodied, trained acrobats.

They were neither.

“Are you certain you’re up to trying this?” Adults could often suck it up and muscle through pain in an emergency, but that was asking a lot of a seventeen-year-old.

“Yeah.” Kayla straightened her spine, her mouth set in a resolute line. “What next?”

Cate hesitated—but only for an instant. If the tools and techniques at your disposal were limited, you worked with what you had.

“I’ll take your hands and climb up on your thighs. Once you feel steady, I’ll put my feet on your shoulders one by one, still holding hands. When I lift my second leg, you straighten up as best you can. After we stabilize, I’ll let go of your hands and you grab the back of my calves, down near my ankles. Coming down, I’ll take your hands, bend my knees, and jump forward.”

“Let’s give it a shot.”

As Kayla got into position, Cate moved behind her. Grasped her hands. Stepped up onto her thighs.

So far, so good.

Now came the tricky part.

Cate lifted one leg to Kayla’s shoulder. Filled her lungs. Pulled herself up and stepped onto Kayla’s other shoulder.

The girl wobbled as she tried to rise from the squat position.

“You’re doing great, Kayla. Give yourself a few seconds to adjust to the weight.”

“You . . . you aren’t as light . . . as you look.”

“Sorry.”

Cate looked up. She was directly under the opening. “I’m going to let go of your hands. Stay as steady as you can. I’ll balance myself.”

Or try to.