“Tomorrow?”

Ester looks puzzled. “Nelinha didn’t tell you? She wants you to go outside the ship and try something with the hull.”

“Leidenfrost,” Gem says as we’re suiting up.

He actually says it twice. The first time I don’t respond, because I’m obsessing about my most recent nightmare. I was glued to Captain Nemo’s chair while the bridge filled with green slime….

“Sorry, what?” I ask.

“It’s a kind of shielding,” Gem says. “Different than Leyden guns. Leidenfrost would create a near-freezing sheath of water around the hull.”

He sits on the bench across from me, connecting hoses to his antique dive suit. On the other side of the interior airlock door, Nelinha raps her knuckles on the window. “Red hose in the red valve, Twain,” she says over the intercom. “We marked them for you. And Leidenfrost shielding wasn’t meant for combat.”

“I know, I know.” Gem rolls his eyes at me. “Ever since she became a billionaire engineer, she’s impossible.”

“I can hear you, billionaire gunslinger,” Nelinha says.

Gem grins. Among the many things I never thought I would see in this life: Gem and Nelinha joking good-naturedly with each other.

“Anyway,” he says, picking up his helmet, “Leidenfrost was designed so the Nautilus could dive in extreme temperatures. Like, she could theoretically plunge through an active volcanic vent, straight through lava, and suffer no damage.”

“Wow.” I stare at the exterior door that will lead us into the abyss. “Nautilus, what kind of adventures did you get up to back in the day?”

The sub does not answer, but I imagine her feeling smug. Yeah, kid, if you only knew.

“If we can get our Leidenfrost shield working,” Gem says, “it might disperse energy weapons. Obviously, Nemo didn’t use it that way. No other ships in his time had Leyden cannons. But I have a theory the Aronnax is using Leidenfrost and that’s why it was impervious to Lincoln Base’s electrical turrets.”

I remember the fuzzy aura around the enemy sub on our LOCUS displays. “Okay. So how do we get it working?”

“I’ll guide you,” Nelinha says over the comm. “There’s a damaged conduit just past the starboard aft bulkhead. I have a feeling it’ll need that special Nemo touch, which is why we’ve gotta send you, but otherwise, it should be a simple fix.”

“If we weren’t doing it a hundred meters underwater,” I say.

The Nautilus has stubbornly refused to budge from this depth, for reasons none of us understand. I can’t shake the sense that she wants us to be in this particular spot, though there is nothing around us on the LOCUS but the yawning canyon of the Palau Trench.

“You’ll be fine,” Nelinha says. If I didn’t know her so well, I might miss the nervousness in her voice. “We’ve pressure-tested the suits. They’re better than anything modern navies could design.”

Still, we’ll be the first people to use them since the 1800s, at a depth where only the best modern technical divers with nitrox tanks should work.