No reaction is faster than reflex. In a heartbeat, I'm up to my armpits in swamp muck, held up by one ice axe sunk deep in a nearby hummock. Thank god I'm not wearing my backpack. It takes more strength than I thought I still had to drag myself back to firm ground, kicking off the cords of what feel like roots around my ankles. Then I'm free, the world around me spinning from my oxygen-deprived headache. I struggle upright. When I regain control of my hands, I unclip my other ice axe from my harness and sink them both into the peat, crouched over them like a wet cat. The hummock shudders.

"Yeah, you just try to sink me, you oversized excuse for a mud puddle," I growl, panting. Even if it takes me down again, I'm still tied fast to a rope whose other end is secured back up where Liu is. I wipe my headlamp and goggles on one sleeve to clear the mud splatters, and look around for Krüger. He's found a hummock near him, too. Right now he's lying on it facedown, head on his arms and one leg still twisted behind him, stuck in the mud. Mahaha must be holding him.

"Tobias!"

He doesn't respond. Unless he managed to keep his day pack when he fell—unlikely, given that I don't see it on him—he's been down here without food or drinkable water for some thirty-six hours. Not to mention the shitty oxygen, and probably little to no sleep. I need to get to him.

"Tobias, tap if you can hear me."

He stirs slightly, then manages to free one arm and tap the peat. Good, still conscious. Something flutters at the bottom of my vision, and I look down to find several brown butterflies perched on my arms. I drop my elbows sharply. They flutter off, but hover beside me, waiting to land again.

"Stay there," I say, to Krüger again. "I'll try to get to you."

The ground trembles again the moment I shift my stance, sitting back on my heels. I engage my headset. "Lingmei?"

"Up here." Her voice trembles.

I look up. Her headlamp flickers like a star through the fog, which has gotten thicker since the ground started moving. Wisps of steam form sluggishly over the mud and peel off to join the heavy air. The swamp itself is room temperature, bordering on lukewarm—so much decomposition generates a not-insignificant amount of heat when there's nothing to take it away.

"Do you have the defroster with you?" I say.

"Yeah."

"Good. Listen, I need you to do something for me. Can you see the little patch I chipped out near the end of the tunnel there?"

"M-hm."

"Take the heat to that, so the water gathers. Then when I say so, I need you to sweep that water down into this cave."

Through the microphone, I hear her pull herself up to the rough patch and flick on the defroster. "Ready," she says after another minute.

"Perfect. Now, sweep it."

She does, at the same time that I pat the ground beneath me. The water patters down into the muck where I first landed.

The still-trembling ground pauses.

"Did it work?" asks Liu, like she's already guessed what I'm testing. I trained stray dogs this way back on earth. If I can get Mahaha to associate the pats with letting me move and getting the water it really does seem to love, I can buy my way across the swamp. I have to spare a huff of laughter for the absurdity of clicker-training a hostile moon.

I sit up slowly again, then try dropping to one knee, moving my hand, and returning to my initial crouch. The ground stays still. "I think it might have. Get another round ready. Chip up the ice if that speeds things up."

She switches off speaking mode, and I hear the tink of an ice axe from the roof of the cave. She gives it a couple swings, then pauses. The next sound is the rapid-fire kicking of a pair of crampons over the ice. I have to smile. That's what I would have done.

After maybe a minute of kicking, the sound stops again. "Ready," says Liu when she's melted the new pile.

"Go."

I pat the ground again, and this time move to the edge of the hummock, towards another one within stepping distance. The ground shivers, then abruptly goes still as the new round of water hits it from above. A few ice shavings fall with it, making plops in the swamp. That, surprisingly, doesn't seem to bother Mahaha. They'll melt almost immediately, so I guess that makes sense—though now I'm wondering why Mahaha doesn't just feed itself if that's the case. I shelve the question for later inquiry.

"Lingmei? Try with just the ice next time. I think it'll be faster."

Sure enough, ice works, too. On the next round, I make it to the second hummock. Mahaha is a fast learner—dog-like, like Liu and Krüger predicted. By the time I'm within a few jumps of Krüger, I only need a water gift every other pat. I make the last jump and crouch down beside Krüger, shaking his shoulder. "I'm here, buddy. Wake up."

He lifts his head, bleary-eyed. "Boss?"

"Are you hurt?"

"I don't think so..."

He's borderline delirious, so I don't trust that, but I'll have to take it until I can actually check for injuries.

"Where's Lingmei?" he says.

"Up above. Do you think you can make it back to where I started if I help you?"

He pushes himself onto his side, and I help him sit up. His foot's still trapped.

"Do you still have your knife?"

He shakes his head. I dig a small folding one from my pocket instead, hoping it will be enough. Liu sends down more ice in exchange for letting me sink my hand into the swamp. There are tendrils wrapped thick around Krüger's ankle. The ground around us shudders as I cut the first of them, and I stop immediately.

That explains why the moon can't bring down its own ice, at least. Any piece big enough to fall from the surface and tumble through the tunnels would tear into these tendrils like a wrecking ball, damaging Mahaha's brain. The moon, clearly, can feel it.

I have to do this by hand. At least the strands are tough enough that I could hardly snap one by accident as I wrestle with them. Krüger finally pulls free. I help him to his feet, keeping a firm grip on his arm as he sways dangerously. We make it halfway back to my starting point before the shaking hummocks knock him to his knees again.

"Need me to send down a water bottle?" says Liu before I have a chance to ask.

"Yes. And an electrolyte packet... actually, throw that in the water before you send it down. I've got the blue rope tied to me, but if you pull up the green one, you can tie the bottle to that and swing it over."

She accomplishes this in the span of a minute. "Bottle coming down," she says, and I turn up my headlamp so she can see where I am on the ground. In another minute, she's gotten the bottle swinging like a pendulum on a rope arc long enough to reach us.

"A bit further... left... bit more left... got it!"

I snag the rope and bottle. Liu reels in the empty rope while I make Krüger drink. Addressing the dehydration at least should get him up to the ice tunnels, where all of us can rest and eat something. That "something" won't be much, though. We've only got one small meal's worth for the three of us left in the packs.

In another half-hour, Krüger can stand unassisted, though exhaustion still makes him markedly unsteady. I can confirm his lack of serious injuries, at least. He admits he's probably more bruised than Kwon was after Mahaha attacked her, but stress and adrenaline mask the pain. We set out cautiously across the swamp again. This time, we're one jump from the first hummock I found when the ground shakes so hard, water splashes against the sides of the one we're standing on. Krüger and I both crouch.

"I don't think it's going to let us go that easily," he says.

I set my headset to speaker mode so we can all talk together. "Lingmei? It doesn't want to let us reach the exit. Any ideas?"

"More water?" says Krüger doubtfully.

"I think we need more water," says Liu a moment later. "I adjusted the amount of ice I sent down while you two were moving around, so she got more when you moved further. I think she'll let you leave if I reward her with enough."

Liu did catch on to what I was doing. And then built on that training and association just like I would. "How long do you think it'll take you to scrape off enough?"

There's a long pause, then she says, "I think I have a better idea."

"Do tell."

"You saw the ice stalactites up here, right? Well, I got a better look at them, and some of them are really fragile. Like, ready to break off. I think I could knock one down."

That would be the motherload. Some of those things were bordering on two and a half meters long; each would be litres and litres of water. They wouldn't do much damage to the swamp if they fell point-first, either. The ones I saw were sharp and slick, and the tendrils are tough enough to take a hit from ice only ten meters above our heads.

"I like that plan," I say. "Just don't hit us with any of them when you send them down. And drop them straight if you can."

"I'll try."

Her light in the cave ceiling bobs about as she puts together whatever miniature wrecking ball she plans to bring down a chunk of the cave ceiling with. In another minute, the distinctive tink of an ice axe sounds near the ceiling. It hits a stalactite several times before a rattle indicates that Liu has managed to hook her target. She gives the rope a hard yank.

Ice snaps. The stalactite hits the swamp with less of a splash and more of a wet slicing sound, swallowed in a moment by the murky water. The ground's tremors stop. Through my headset, I hear Liu still holding her breath.

Nothing happens. My theory was correct.

"That was perfect," I say.

"Another one?"

"See if it lets us to the last hump first."

It does, though the tremors return as we crouch there instead. Liu nets a second stalactite in half the time. "Incoming!"

This one splashes louder. It's followed by a cracking sound from the ceiling. There's another splash, then a third, fourth, and fifth in quick succession. A long pause is followed by a final stalactite casualty. The swamp stays absolutely still.

I'm the first to speak. "If that doesn't let us up, I don't think anything short of a ceiling collapse will. Can you send down the climbing gear for Tobias?"

She does. I set up a manual winch system that will get us back to the cave ceiling, then make Krüger go first. Liu helps him over the ice rim at the top.

"Thanks, buddy," I say, patting the ground before I follow.