America and I exchange a glance, and then he looks at my ankle. "You want me to help you?"

I run my tongue across the back of my teeth. "Fine," I say.

He puts his arm around my waist and helps me limp along as we make our way down the tunnel to Elias and Star. As we travel, the echoing of water becomes more pronounced. The tone and resonance of our own footsteps changes, taking on a hollower sound. My heart pounds against my ribs. We are drawing closer to something—something big.

We follow the gradual turn in the tunnel as the passageway widens around us. I shine my light ahead, and Elias and Star come into view.

The beam of my headlamp casts them in dark silhouettes—two astronauts standing on a ledge at the opening of a chasm. The tunnel forms an archway above them where it expands into a massive chamber. White stalactites ridged with rings of pink and brown hang from the roof of the entrance like giant calciferous teeth in the mouth of some enormous beast.

After traveling a few more yards, we reach the others. America lets go of my waist as we gaze out into the abyss. I stand with my toes as close to the steep slope as I dare. The cavern is nearly a hundred feet deep and extends out wider than a football field on both sides. The four beams of our headlamps dance across the ceiling and floor, becoming lost in the shadows of the cave when they pass over the far end of the chamber.

To the left, rust-colored water drips from a set of stalactites. The sound beats like the ticking of a metronome, amplified by the echo of the huge space. The stone columns extend towards the base of the cavern, stretching toward their partner stalagmites like prison bars. The dripping water collects in a divot the size of a small tide pool carved out between the stalagmites. Water trickles from the smooth, worn-away stone in a small stream like a tiny slip-n-slide toward the pit at the center of the cavern.

The water there is a stagnant pond. The beam of my headlamp doesn't even penetrate its surface. It's a pool of thick, opaque crimson—like a pool of blood.

A chill shudders through me as I think about the monster that attacked us from the air when we first landed. It adapted instantly when we went into the caves, snapping its wings back so it could crawl through the ground. That creature had tentacles, too. What if it also had gills?

I shine my light on the opaque surface of the water, expecting a tentacle to suddenly shoot up from beneath it, or the water itself to pulse and birth some sort of beast into the cave. The larger worm we crossed paths with in the tunnel wasn't viscous, but it was still dangerous. Additionally, it's no guarantee that the next worm we run into won't be infected like the first set.

I search for any sign of movement beneath the surface, but I see nothing. Everything is still—silent—except for the tick of water dripping and the breathing of four humans at the mouth of the beast. We are staring into its belly—its lair.

"We should be able to climb down this." America is the first to break the stillness. He tests his weight on the rocky slope leading into the chasm.

I swallow the lump that's formed in my throat. "Maybe we shouldn't go down there. What if there's something in that water?" I direct my headlamp at the stagnant pond.

"Shawn's right," Star says. "I don't have a good feeling about this, America."

"We came here looking for water, didn't we?" he asks. "Why are you both acting like you've seen a ghost now that we've found it?"

"I didn't expect there to be this much of it," I say. "I thought we might just find a small leak that would lead us to the surface. That pond . . . I can't even see the bottom."

America's face softens slightly. "We should at least take a look," he says. "There's water dripping from the ceiling, so maybe we are close to the surface here. There might be a thin spot nearby where we can find a way out. I can go out ahead if you want to wait here. I know your ankle isn't doing so great right now."

"You don't have to do that," I say. "I'm just hesitant. It gives me a bad feeling."

"We don't know what's in any part of these tunnels, Shawn," Elias says. "We could get attacked by something behind every turn. Every choice is a risk. At least here we have a good chance of finding a way out. This chamber is the most promising spot we've found so far."

Star and I are silent for a few seconds.

"As crazy as it sounds," Star finally begins, "that actually makes me feel a bit better." She looks to me, as if checking to make sure I'm okay with it.

"Fine," I finally say. "Lead the way, America."

He nods, and we follow him down the side of the ledge in single file. Elias goes just ahead of me, and Star brings up the rear. The rocks form a structure almost like steep steps, but the slope makes it difficult to find a good handhold. I lower myself to my ass and scoot along, not wanting to survive an attack from monstrous alien worms only to slip and fall to my doom on a set of stairs.

It isn't long before we reach the bottom. With the exception of the outcropping of stalagmites around the dripping water, the base of the chamber is smooth, like the stone has been worn away and polished by something.

I shine my light at the stalactites on the ceiling dozens of yards above my head, casting dark shadows around them. I imagine tiny maggots writhing and churning in the darkness just beyond where the light touches. The beam dances across the stone teeth, searching for a gap that might lead to the surface, but the rough texture makes it too difficult to gauge depth. Even if there is a way out up there, lord knows how we'd managed to get to it.

The four of us continue around the stalagmite pool and the pond in the center of the cavern. Despite what America and Elias said, we all give it a wide berth, none of us wanting to get too close and disturb it.

Our footsteps echo hollowly throughout the chasm. I glance off to my left, tracing my light along the side to search for an offshoot that might lead out. The smooth base of the cavern slopes up slightly until it reaches the rough stone wall. A few cracks and crevices ripple the surface, but none are large enough for a human to fit through.

"Let's head towards the back," America whispers.

"Sounds good," Star responds quietly.

The other three direct their lights toward the shadows on the far side of the space, but I bounce mine around the rest of the cave, afraid that if I leave any spot in darkness for too long, some sort of alien monster will materialize out of the thick, cool atmosphere and attack us.

"Do you see that up there?" Elias whispers.

I turn to where the rest of them are looking. In the corner at the far end of the cave, the floor rises a dozen feet or so, leading to a wide offshoot—a second, smaller chamber. A slow, trickle of water spills over it. It's only enough to make the ground around it damp, but it's something.

"You think it might lead us out?" I keep my voice low as well. Even though none of us say it, I think we are all afraid to speak too loudly in this place—like if we disturb the silence, we'll wake something up.

"Let's check it out," America says.

The pain in my ankle flares as we climb toward the second room. When the slope levels out at the top, I pause, panting to catch my breath. The others continue on while I brace myself on the side of the wall to rest, but my fingers slip over something slick and web-like. A chill of disgust shudders up my body as I look where I've placed my hand.

Instead of the thin covering of mold that speckles the surface of the rest of the cave, mucus-like algae coats the walls here. It crawls across it like spider webs—stretching across cracks and crevices like the algae coating the ground around that other starship we found.

My stomach does a flip in my gut as I think back to the conversation we had while we were waiting for the worm to pass in that tunnel. Elias said he thought the webbing around that other starship was something the parasites created to form a hibernation pod for their hosts. If that's the case, then that means—

"What the fuck are these things?" Star asks, cutting me off mid thought.

I shine my light at where the others are exploring the back of the tomb. Lumps of thick, pink webbing cover what look like coffin sized stones. My heart pounds against my ribs as sweat slicks my brow. The image of the webbing on the ancient starship pulsing right before those creatures burst from their cocoons flashes through my head.

"We need to get out of here," I whisper. "We need to get out of here now."

I take a step back, and my heel hits something, sending a ping through the cave. It feels like I've kicked a rock, but the sound is wrong—hollow. My heart races as I flash my light down to my feet. A spherical stone coated in pink mold and webbing sits at my feet. Next to it, a few specks of white flicker, like tiny pebbles. My hand shakes as I reach to pick one up, but I feel like I already know what it is.

It's a tooth.

A human tooth.

I choke back a scream as I drop the incisor to the floor. It bounces off the spherical stone next to the other teeth, creating the same hollow clank it made when I accidentally kicked it. It's like something striking metal, or glass.

What the fuck.

Before I can stop myself, I reach down, wiping some of the mucus-like webbing away from what I thought was a rock. The algae comes away easily, like cleaning a splatted bug from a windshield.

It only takes me a second to realize what I've uncovered. It's a helmet from a space suit—a helmet that is identical to the one I am wearing, down to the letters "ICC" carved into the white plastic around the headset.