I turn to face in the direction Star points, but I think I already know what I'm about to see, and I'm not sure if I want to look. The shacking beam from my headlamp flashes over the rough, rocky walls of the cave before finally joining the lights from Elias and Star's helmets.

About twenty yards down the tunnel, where we all would have been if we had started walking just a few seconds sooner, a pile of rocks has burst out from the wall of the cave. Rubble is scattered across the ground like someone lit off dynamite behind it. The smacking and clicking sound intensifies as the massive head of a worm emerges from behind the explosion.

"Oh shit, oh shit," America hisses under his breath.

The worm's head snakes around, twisting and turning as it sends waves of sickening croaks down the tunnel in both directions. Its hideous face has no eyes, just a round mouth with a ring of teeth leading back into the darkness of its throat. It's like staring into a black hole.

"What do we do?" I ask.

"Everyone be quiet," Elias whispers. "Get back against the wall, and remain absolutely still."

We all keep our beams of light fixed on the monster as we slowly shift our bodies to back up against the side of the tunnel. I press myself against it, wishing I could morph into it and become a part of the stone.

"What's it doing?" Star asks quietly.

The creature continues to release deep, throaty croaks as it cranes its enormous head around.

"It's searching," I say. "It's blind. It has to use echolocation to see."

"Yes," Elias whispers. "And that's why we have to remain absolutely quiet and still. If we don't move, it can't see us."

I hold my breath, afraid even the sound of my respiration will be loud enough that it will find us. The monster is huge—bigger than any of the creatures that hatched from that spaceship and chased us into these tunnels. Those were not much bigger than a human. This one's head reaches almost from the floor of the tunnel to the ceiling. It must be ten times the length of the other creatures.

Were the ones that chased us down here babies? Is this what the adult monster looks like? I swallow down a huge lump in my throat. My entire body shakes with fear. A hand grips mine, and I squeeze back, even though I'm not sure whose hand it is. I don't know why, but physical contact feels good. I feel stronger knowing I'm not alone right now.

The monster releases a grunt, and then its body wriggles, propelling it forward so its face touches the far side of the tunnel. Its teeth protrude out from its lips, flexing and contracting in its jaw. With another thrust, it latches into the side of the wall in front of it. Its body continues to contract and thrust, moving it forward inch by inch as it chews into the dirt.

Sweat drips down my neck. My legs shake beneath me as I try to hold myself still. None of us say a word as the face of the creature gradually disappears from view, leaving behind only its body. It looks like one large, wriggling intestine. The throaty, croaking grunts are replaced by the sound of chewing and gravel crumbling.

"Are we safe to move yet?" Star whispers.

Before we have time to answer, a rumble echoes through the tunnel. More rocks tumble from the side of the cave where the worm came from. With a burst, tentacles crack through the wall. Dirt and dust explode into the tunnel as the tentacles shake themselves out, stretching in the open space.

"Get down!" America shouts. The hand gripping mine tugs, and I'm pulled to the ground just in time to duck under the enormous tentacle as it swings over us. I roll over and lay flat on my back as it smacks around the space like a whip.

There is a thump as it whacks the side of the tunnel, followed by a scream. "Oh fuck!" Star cries. "Help!" She is pressed up against the wall, a pained grimace on her face as the tentacle pins her at the chest.

"Stay quiet," Elias says.

"It's . . . crushing me." She grits her teeth. "I can't breathe. Fuck." Star pushes against the tentacle, trying to pry it off her, but the arm is massive compared to her. "I can't get out!"

With a pulse, the tentacle wriggles and squirms, releasing the pressure on her. She gasps, but then before she has the chance to even move, it slams back into her. The tip of it curls as it retracts toward the monster. It catches and grabs her around the waist.

"No!" I scream, forgetting we need to keep quiet. I leap to my feet and charge toward her as she is ripped down the tunnel by the massive arm.

His screaming fills the space as it smacks her against the side of the wall. She reaches her hand towards me, and I dive and grab it. My gloved fingers just barely catch around hers. We both fall to the ground on our stomachs as the monster continues to whip and pull her in.

"Don't let go, don't let go," I chant, as much to myself as to her.

The arm yanks at her again, and my fingers slip through hers. Right before I lose my grip, I throw my other arm out to her, clasping her at the wrist. The creature drags us across the rough, rocky floor of the tunnel as it pulls her in.

"Shit, shit!" she gasps. "Shawn, help!"

I slam the toe of my one good leg into the ground, trying to find a grip, but it's no use. My boot bounces off the rocks and scrapes through the dirt, unable to anchor anywhere. Pain burns through my body as the slamming and banging bruises me everywhere.

Suddenly, hands clasp around my ankle. "I've got you!"

I glance over my shoulder. Elias strains to hold on to me, digging both heels into the dirt as we're all pulled in. The monster is too massive. The three of us won't be able to hold it off.

"America, help!" I shout back. I can't find where he is. All of our headlamps are flashing around the tunnel like strobes, making it impossible to tell exactly what is going on. Finally, my beam finds him. He's already running toward the three of us at a full sprint.

Instead of grabbing on to us like Elias did, he rushes past Elias, Star and me.

"Let go!" He throws all of his weight against the mass of the tentacle, just forward of where it's wrapped itself around Star. He slams his clenched fists into the thick, fleshy arm and shoves it towards the side of the tunnel. With both arms, he pins it against the wall, digging his elbows into the writhing whip.

The force tugging at Star releases as the tentacle bucks and loosens its grip. I yank her wrist as hard as I can, pulling her on top of me. Our helmets collide with each other, sending the ringing ping of glass-hitting-glass through the entire cave.

"Run!" America shouts.

The world blurs around me. A hand grabs me by the wrist, and I'm pulled to my feet. Everything goes dark for a second as intense pain bursts through my head, stemming from the top of my spine. I can't even feel the pain in my ankle as I'm dragged along.

I trip over my own feet. I throw my hands out to catch myself, but before I hit the ground, America grabs me, wrapping his arm around my waist. He lifts me and carries me along as he continues to run.

Tears burst from my eyes as the pain in my head throbs against my skull. Screams fill the tunnel, and I'm sure some of them are my own.

"Shawn, stay down," America says to me as he sets me on my back. Everything in me hurts. His arm covers me, pressing me to the ground as I stare at the ceiling of the tunnel.

The tentacle whips against the wall one last time before retreating towards the monster. I breathe in heavily, but America doesn't lift his arm off me. Above us, a gigantic wing sprawls out, filling the entire tunnel. It shakes itself like it's stretching. It doesn't even have the room to completely open in the tunnel. The joints in the thin, branch-like structure bend and flex like a clawed hand.

The wingspan of this thing is incredible. The creature itself must weight several tons at least, so I shouldn't be surprised. Fully grown, in order to lift itself into the air, its wings need to be enormous.

The bat-like wing flaps as it moves through the tunnel. Pink dust swirls up from the floor and walls, blinding me. Beyond the glass of my helmet, there is nothing but a sea of brownish pink.

Another bang crashes around us, and then the cave goes silent. The sound of my own respiration is the only thing I hear. The cloud of dirt around me glows in the beam of my headlamp as it settles. America loosens his grip on me.

With one hand, I wipe the fog of mold and dust that has settled on the glass of my helmet. I blink as I take it my surroundings. The tentacles are gone. I lift my head just enough to see the body of the monster. Its wings have collapses against it as it continues to inch itself along.

Next to me, America lies on his stomach, one arm loosely covering me. A film of reddish dust coats the helmet he inherited from Devin.

On my other side, Star lays on her back. Her spacesuit is scratched and coated in dirt, including the glass of her helmet. I can't see her face either. Other than her chest moving slowly with respiration, she is completely still.

No one says anything for a minute. No one even moves. I can still hear the sounds of mastication as the worm continues down the tunnel.

"Is everyone okay?" Elias finally asks, his voice coming from somewhere behind me.

"Define okay," Star responds.

"Alive." Elias doesn't miss a beat. "Is everyone alive?"

"Yes, then," Star says. "But that's the about the extent of okay I'll give it right now."