“Wait,” Pablo said. “I hear it, too.”

“How could—”

“It’s … not static. It’s a river.”

He continued on, his pace increasing with the prospect of a change in scenery. Sure enough, with each step the sound of rushing water grew, and not a minute later the tunnel entered a large underground grotto.

The expansive space was eerily lit from below in emerald green. It took no imagination to guess the source of that light, yet Tania still found herself breathless at the beauty on display before her. Wave patterns danced lazily across the uneven ceiling, reflected off the rushing water below.

The river flowed in from Tania’s right, cascading down the center of the cave. In places it appeared to be only centimeters deep as it flowed over smooth rock and around larger boulders that must have fallen from the ceiling millions of years ago. She based that estimate on the way they appeared to be melting into the floor.

In other areas the water pooled into imposing dark patches of a depth she couldn’t begin to guess. Here the black liquid flowed more slowly, growing to its widest point almost exactly where their tunnel had bisected the room.

Directly in front of where she stood was a bridge of sorts. Ejecta from when the shell ship had bored through the cavern wall lay in an uneven line, piled as high as a meter above the surface of the river. The water flowed around the new obstacle with visible churn, its ancient route suddenly obstructed.

At the end of this bridge was the shell ship, nose half buried in the pile of rock it had propelled into the cave. It had come to rest at an angle, allowing Tania to see most of one side. The surface of the vehicle held deep scars—grooves spiraled around the front half in a corkscrew pattern.

Near the center was a gap in the fuselage, just like the one Skyler had seen in the tunnel near Belem. The emerald-green glow that so beautifully illuminated the room came from within.

Caught up in the grandeur of the view, Tania almost failed to notice the lone subhuman corpse. It lay facedown in the black waters that gurgled against the upstream side of the land bridge. “Looks like at least one made it this far,” Tania said, pointing.

Pablo had been about to step out onto the first clump of debris, but paused at her words. “All the way down here, only to slip and drown.” He shook his head.

He also didn’t continue toward the ship, Tania noted. She understood the hesitation, too. Each of the other objects had been protected, as it were, by a challenge. In Belem, thick mists had blanketed the area and concealed subhumans transformed into armored killers. In Ireland, Skyler had found a dome that manipulated time itself, and subhumans that seemed capable of utilizing that advantage. She didn’t know what the woman Samantha had faced near Darwin, but she had heard in her tone the implication of similar dangers.

So what is it here? The cave itself? Could the challenge of navigating such a place be what the Builders hoped would serve as protection? She thought … maybe. Her eyes glanced at the 3-D route her suit was automatically generating as they moved. Maybe the Builders hadn’t counted on such technology. Or perhaps that was the point. This would have been a nearly impossible task just a few hundred years ago. Maybe this was all some way to assess a planet’s technical capability. Prior to first contact, as she still stubbornly hoped, or prior to invasion, as Neil had theorized.

Yet the presence of subhumans that had tried and failed to reach the thing filled her with unease. Perhaps the aliens planned for something more, something deadly, but their material source—subhumans—had not made it. Not yet, anyway.

Pablo went to one knee and began to rummage through his backpack. He pulled out a coil of climbing rope and began to tie one end around his waist.

“What are you doing?” Vanessa asked him.

“The water. It makes me uneasy.” He walked to Tania and looped the rope around her waist twice, then handed the rest to Vanessa. “I had a … vision, I guess. Slipping on that bridge, pulled down by an undercurrent and swept into darkness.”

“A very wise precaution,” Tania acknowledged. She looked at the water with more concern now. Before it had only registered with her as a pure liquid, an erosive fixture in this ancient place made dark only by the underground location. Now the obsidian black, rippling surface seemed alive. The entity the room been missing. An enemy to focus on.

“I’ll go first,” Pablo said. “Tania, only come out as far as you need to.”

His tone left no room for debate. Vanessa moved to stand beside a large boulder that had rolled to a stop at the lip of the river. She walked behind it and dug in her boots, positioned so the rope had to wrap around it. Satisfied, she nodded at them to proceed.

Pablo took each step with almost maddening care. Probing, testing. A little weight, then more, then a shift in stance to place himself exactly halfway between this step and the last. More probing, and then the final movement. Tania tried to focus on his foot placement, to spot for him and remember where he’d stepped so she could follow exactly, but the shell ship kept pulling her attention to it. The more she stared at that steady green glow, the more she thought it had a pulse to it.

“Whoa!”

Pablo stumbled, breaking her semi-trance with his voice and sudden movement. Instinctively she gripped the rope tighter, braced herself for the worst. Suddenly she imagined him going in the water, pulling her with him. This made her realize with horror that she wouldn’t drown. No, her fate would be something even worse. The suit would keep her alive for hours as she drifted down the underground river until the water pinned her against a wall in some deep, dark place, until her air ran out and she suffocated. Tania slammed her eyes shut and forced that vision away. She thought of the avocado grove on Space-Ag 12, the sound of the artificial breeze rustling the branches, and Neil. Her pulse dwindled.

The man in front of her laughed, nervously. It had only been a loose rock, she saw. The gray object rolled into the black water and vanished. Pablo paused for a moment, gathering his courage again before trying another position. Tania waited, found herself focusing on the green glow again.

Finally Pablo reached the crashed vessel. He placed his hand on it for support without any apparent concern that the contact might cause something to happen. Tania wanted to shout to him, tell him not to jostle the thing, not to wake it, but his hand was already resting on the scarred surface and nothing happened as a result.

She let out her breath. He was five meters away, just a dozen steps or so. Tania moved toward him and felt the rope tug against her waist. She looked back and realized that the maximum length between herself and Vanessa had been reached. “This is as far as I can go,” she said. “Can you move up?”

“I’d rather not,” Vanessa replied.

“It’s okay,” Pablo said. “There’s enough slack. I can make it. Stay put and be ready to go back.”

And just like that, he stepped into the opening on the side of the alien ship and out of Tania’s view. All she could see was the long blurred shadow he cast on the ceiling and walls of the cavern as he blocked out some of the green-hued light coming from within.

The rope that linked her to Pablo started to pull taut. Just when she began to think it might not be long enough, he called out.

“It’s here. I’m going to pick it up … right … now.”

The emerald-green glow vanished, plunging the cave into darkness. Tania gripped the rope in a fist so tight she felt her nails dig into her palm. Something pushed against her. A force, like a concussion wave from a nearby explosion. She almost fell. The display inside her helmet flickered once, then vanished. The static sound of the river coming through her suit’s speaker vanished with it, as did the ever-present background noise of her …

… of her air processor. Gone.

A wave of anxiety swept over her. She slipped again, and in her rush to grab hold of the rope she let her gun drop. The splash of it in the water sounded far away, muted. Her heart pounded. Despite the lack of sound coming in she could hear her own terrified breaths, amplified in the confines of her helmet. She could smell her own fear, hear her own movements, but from the outside world … nothing. No scents. No light at all. Sounds were barely perceptible. Even her sense of touch was only what sensation came in through the protective suit.

All sensation from the outside world, gone.

She screamed for help, the noise of it deafening and yet, she thought, possibly inaudible to Pablo or Vanessa. Tania did the only thing she could think of and crouched down, suddenly feeling like she was on some tightrope over a deep, deep gorge.

Her panic faded enough to allow a single cold realization in: The air processor has stopped. Her suit was dead, all the electronics shut down, possibly fried beyond repair. It took a singular force of will to release one shaking hand from the rope and fumble at the control panel in the center of her chest. She tried to picture the layout of the buttons in her mind, and couldn’t. In her panic she began to punch them at random. Nothing happened. She began to pound her chest.

Calm. Get a hold of yourself.

She hadn’t even realized she’d let go of the rope. Utterly blind, she patted the slick rocks around her for it. Nothing. She extended her hands and felt a subtle change as they entered the water. Coldness bit into her fingers and for a fleeting second she thought the liquid had entered her suit. But no, it was just the outside environment no longer being held at bay by heating elements built into the fabric of her outfit. She splashed around in the water, felt something round, and gripped. The rope. She pulled it from the river and only then realized it was still wrapped around her waist. The realization that she could have found it easily by starting there seemed to stem the growing fog of panic in her mind.

Both sides of the rope were slack. She began to haul in the portion that led to Pablo. Or had, at least. If the rope pulled in without him and the end, or Vanessa at the other—

She couldn’t allow herself to think that. Tania shouted again, at herself this time. “Think!”

There were patterns before her eyes, like the bizarre shapes that appeared on the inside of her eyelids if she stole a glance at the sun. Her foot began to feel cold and she realized it had slipped into the water.

Tania pulled in Pablo’s side of the rope first, and to her horror it kept coming easily, just as she feared. Any second she expected to find the end, dangling loose. Then something—someone—bumped into her. She fell, a hand caught her. One strong hand, gripping her by the upper arm. Pablo or—

A demon’s face emerged from the darkness before her, at the edge of her perception. Faint, stark hints of cheekbone and jawline. Haunted eyes like two emerald stones. The scream she’d been on the verge of letting out died in her throat at the sight of those eyes. They were terrible and beautiful and …

Pablo’s.

He was shouting at her. At first she recoiled, sure he’d been transformed somehow by the alien vessel. But no, she realized, he was simply lit from below. Faintly, yes, but that was all it was. She looked down and saw an object cradled in his other arm. Glowing green lines a hair’s width across covered the surface, emitting so little light, the ground at her feet was still nothing but inky blackness. The triangular object was perfect save for one missing tip, matching exactly with the receptacle she’d seen aboard the ship in orbit.

Pablo squeezed her arm and shook her. He was still shouting. Tania reached up and pulled his head to her visor, turning him so his ear pressed against the glass. “I can’t hear you! My suit has failed!” Tears welled in her eyes as she said the words.

The immune nodded and guided her by the arm. She had to move one slow step at a time, tapping around with the toe of her boot to find a solid place for her weight. Twice she slipped and almost went down, and each time Pablo’s grip—painfully tight—kept her from spilling into the water. Her proximity to spending the rest of her life in a weightless, frigid oblivion forced her to concentrate.

She felt a tugging at her waist and remembered that Vanessa wore the other end of the rope. Tania gripped it and gave it a tug in return. A second later she felt two quick tugs, which she returned. A signal that all’s well. It added to her confidence and she took the next few steps more assuredly. Just like that, her feet were on solid ground. Pablo guided her a few meters onto the pile of rubble that served as a shore and eased her to a sitting position.

To her surprise he plopped the alien artifact in her lap and then vanished into the darkness. Checking on Vanessa, she supposed. Tania ran one hand over the surface of the triangular mass, watching as the silhouette of her fingers obscured the laserlike green lines.

The rope at her waist tugged from Vanessa’s direction, and then the woman was next to her. She crouched next to Tania, probably thought she was in shock. Tania repeated the technique she’d used with Pablo and pulled Vanessa’s face down to her helmet, pressing her ear against the glass. “I’m okay! The suit is off line.”

Vanessa cupped her hands against the glass and shouted back. “Understood. We need to—”

Red light exploded into the cavern. Tania jerked back in surprise as a single, fiery point of light began to float before her in odd lurches. She could see smoke curling away from the red fire and sparks dripping down from it.

A flare. An emergency flare, held aloft by Pablo. He’d pulled it from the backpack he’d left on the shore before venturing across. So their flashlights had failed, too. Anything electronic, she guessed, due to some kind of electromagnetic pulse unleashed when the object was picked up.

The man came to them and handed a second flare, unlit, to Vanessa. Tania saw his lips move. Whatever he’d said, Vanessa nodded back and slipped the spare light source into a pocket. The two of them then launched into a rapid-fire conversation. An argument? No, she thought, just frantic planning.