Zed arrived at the crate cave right on schedule. His growing confidence wavered somewhat, however, as he stood looking down into the darkness before him. The jagged edges of the cave's entrance looked no less foreboding now than when he had stood here with Johns in broad daylight. In the middle of the night, it was even easier to picture the hole as a mouth rimmed with stony teeth.

  “Get it together, Zed,” he muttered.

  He had come this far. A creepy hole in the ground was not going to be the thing that stopped him. Zed forced himself to look away from the pit and focused his attention on the crane system.

  The crane consisted of two arms that looked far too slender for comfort. A cable ran from the end of each and met on a small vertical platform with a foothold just big enough for one rider to place his feet on while holding the upper section just below where the cables attached. A simple set of switches was connected to the right-side arm, allowing the rider to control the crane while riding the lift.

  Zed positioned his feet on the tiny platform and gripped the bars on either side. He closed his eyes and tried to focus on his breathing. His heart rate began to slow. Unbidden, an image of a dark figure crawling out of the hole and darting toward him intruded on his calm. Zed's eyes flew open.

  There was nothing there, of course, just nerves paired with a creative mind, but the damage was done, and his heart resumed its tap dance in his chest.

  “Screw it,” Zed muttered and hit the lift switch with his right thumb.

  The crane obeyed with a groan and lifted him for a few seconds before coming to a stop half a meter above the crater floor. Zed flipped the other switch, which swung him out over the opening in a slow arc.

  Zed had never been a huge fan of roller coasters. It wasn’t that he didn’t enjoy them; once they were moving, he loved the adrenaline rush immensely. However, the dread of the climb beforehand was usually enough to keep him safely out of line. This felt similar, but far worse, because this wasn’t a ride designed with safety in mind. This was a true risk, and any screaming wouldn’t be followed by nervous laughter, but rather the crunch of his body breaking against a rock in the cave below.

  As Zed reached the center of the hole, he brought the crane to a stop, causing him to swing back and forth like a human pendulum. If he had been watching from the sidelines, it wouldn’t have looked like much, but now that he was up here, it felt as if his life was about to flash before his eyes.

  He paused for a moment and tried to get his breathing under control. He should have plenty of air for this little adventure, but there was no need to burn through it any faster than necessary. The crane shuddered slightly as Zed began his slow descent into the inky blackness.

  As he passed the lip of the crater floor, Zed flipped his headlamps to full brightness, but he didn’t dare look down. After what felt like an eternity, but was probably only two minutes, Zed felt the base of the metal footplate come to a jarring stop. He turned off the crane and took a tentative step back off the footplate and onto solid ground.

  The relief of no longer dangling over an abyss completely overwhelmed any uneasiness he might have felt at finding himself in an alien cave. At least, it did for a moment.

  As Zed turned, his lights revealed the unusual rock formations that made up the cavern around him. He realized he was standing in the middle of the smaller crater created by the rock that had punched through the floor of the crater above.

  Zed had been in a few caves on Earth, and this didn’t look like any of them. There were no stalactites or stalagmites, which made sense considering there was no water to form them. Sure, he’d seen the scans, but being here in person was an entirely different experience.

  He had a vague memory of hearing some professor that his parents had invited to dinner talk about the caves of Mars. While the old man's name escaped him, he clearly remembered the dusty smell of his faded green cardigan and the intense passion he had for the geology of the red planet.

  Usually, Zed would have just tuned out his parents’ academic dinner guests, but there was an infectious excitement in the way the man spoke about the potential of lava tubes beneath the Martian surface. Zed was fairly certain he was standing in a rather large example of such a lava tube.

  The professor had been of the opinion that any Martian habitats should have been built in lava tubes, feeling that constructing them in craters was wasting the easy radiation protection the caves offered.

  Looking around, Zed had a hard time imagining the mess hall setup in this ominous space. The jagged layers of rock cast sharp shadows that shifted back and forth as Zed scanned his surroundings.

  As he turned his attention to the ceiling, a damaged section caught his eye. It looked like a large stone piece had given way, perhaps during some kind of earthquake. The layers of rock had peeled back at the edges like the paint of a mural, forming a distinctive shape that Zed immediately recognized.

  Calling up the 3D scan of the cave system that he’d put together from the drone footage, Zed used his CIG to navigate to the large central chamber. He flicked his fingers apart, scaling the miniature cave until it reached an equal scale with the real one. Zed carefully rotated and shifted the semi-transparent room until he saw the same damaged roof sections. He made small adjustments until it aligned with the real one and then locked it into place.

  Satisfied, he imported the 3D route markers he had created as breadcrumbs to lead him through the cave. A line of little blue spheres popped into existence and wound their way down one of the side passages.

  Zed smiled as he imagined himself as that ancient video game character “Pac-Man,” gobbling up the blue dots as he went. He just hoped there were no ghosts lurking around the corner.

  With his path laid out before him, Zed picked up the sample case and started down the side passage, chasing blue dots as he wandered ever deeper into the dark unknown.

  Zed had never considered himself athletic by any stretch of the imagination. He had never played sports or even exercised consistently. If he had to describe his body type, he would have called it “doughy.”

  The gentle Martian gravity usually made up for his lack of muscle, but not today. Despite his careful planning of the route to the chamber entrance, he hadn’t taken into account the strength it would take to walk, crouch, and squeeze his way there.

  An hour and a half in, he was starting to worry that even if he made it there, he might not have the strength to make it back. The sample case that had been a mild hindrance at the start now felt like an anchor he was being forced to drag into the Martian depths.

  He hoped he wasn’t near anyone when he finally peeled himself out of this suit because, after hours of marinating in his own sweat, even he had to admit he was starting to smell pretty vile.

  The blue dots continued on, passing through a section of cave where the ceiling came down to chest level. It went on like this for about a hundred meters.

  On Earth, Zed would have simply stooped and walked through, but everything was far more awkward and complicated when wearing the weight and bulk of something that had to be strong enough to withstand the rigors of a hostile planet while also packing in enough tech to create its own little atmosphere.

  Just stooping was not a real option, so Zed found himself leaning forward slightly while also bending his knees in a half squat. He felt like some kind of mutated crab as he shuffled sideways, chasing the dots ever onward.

  When Zed finally emerged on the other side and the ceiling rose once more, he uttered a low groan as he straightened his back and legs.

  “Time for,” Zed took several panting breaths, “a little break.”

  There was no comfortable way to sit without a chair while wearing a turtle suit. The flexibility was far better than the suits of old, but sitting cross-legged on the floor was still out of the question. Zed locked the exoskeleton that ran up the sides of his legs and leaned against the wall. It was better than nothing.

  Zed lost track of time in the dark. As he followed the path his CIG indicated, he was struck with the horrifying thought that the map could be wrong or the data could become corrupted while he was still down here. The odds were certainly low, but he knew for a fact that there was no way he could find his way back without the waypoints to guide him.

  Before he could dwell further on that nightmare, he was confronted with another.

  Zed caught a glint of metal in the light of his headlamp. As he got closer, he saw that it was the ladder the previous explorers had attempted to use as a bridge to cross the bottomless pit. The pit where Jacob Ens had met his end.

  Now that he was here, it wasn’t hard to imagine how things could have gone wrong. It wasn’t just about how deep the pit was or how long the ladder was. It was the ceiling. As you crossed the makeshift bridge, you had to crouch lower and lower to avoid the ever-descending stone roof. By the time you reached the other side, you were army-crawling the last meter.

  Zed could see it so clearly. Jacob, being the good leader that he was, would have insisted on making the first crossing. He was probably halfway when things started to get awkward.

  Had he bumped his helmet against the ceiling and thrown off his balance? Or maybe he just lost his grip on the ladder when he tried to transition onto his stomach.

  The passage suddenly felt smaller than it had a moment ago. Zed turned his back to the chasm.

  Deep, steady breaths. Don’t freak out. Do NOT freak out. I’m smaller than Jacob was. It’ll be fine. I’m just going to crawl the whole way, and it will be just fine.

  Zed turned back to the ladder bridge, aware that each step toward it felt like it was tying a new knot in his intestines.

  He knelt at the end of the ladder. It had been secured with pins hammered into the stone. Of course, it had only been secured on this side because no one had made it over.

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  “I’m going to have to do this one-handed,” Zed said aloud.

  The sample case. It wasn’t like he could just kick it along in front of him or even push it. It could fall, and that would be that. He would have to hold onto it the entire time.

  Zed knelt down and crawled to the ladder bridge, dragging the case along behind him. He put a gloved hand on one of the rungs and gave it a push. It held firm, so he put a little more weight on it. So far, so good. There was some comfort in knowing that whatever had happened to Jacob hadn’t been because the ladder gave out.

  The ladder wasn’t wide enough, and the gaps between the rungs were too large for Zed to safely push the case along in front of him as he crossed. He attempted several different positions, but they all put the case in too much danger of falling since he couldn’t hold onto the handle.

  Finally, Zed settled on a method that felt like his best option, even if it looked more than a little ridiculous.

  “Here goes. Wish me luck, Douglas.”

  As per his design, Douglas said nothing.

  With great care, Zed lay face-first on the ladder and dangled the case over the abyss. Once he had inchwormed his way up enough, he reached around with his other arm to grip the case handle with both hands as it hung directly below him.

  In this way, he could push himself forward as if climbing the ladder with only his feet while keeping both hands on the case. Sure, he’d scrape the hell out of his faceplate, but at least it was nearly impossible to fall. At least that’s what he was going to keep telling himself.

  With his hands clutching the case to the point where his fingers were starting to fall asleep, Zed’s only option for moving himself along was to push with his toes. At that moment, his toes were still on the rock. They kept slipping and losing purchase on the surface as he tried to force his body along the makeshift bridge.

  Every time they slipped, Zed’s knees would slam into the ladder, sending a shudder through his body and down his arms.

  Zed took more care with how he pushed and was able to work himself forward enough to get his boots to the first rung on the horizontal ladder. He breathed a deep sigh of relief, briefly fogging his visor.

  Now there was truly no turning back.

  The biggest downside to crossing this way was that Zed had no way of adhering to the old “don’t look down” adage that people so often used when dealing with great heights. Worse still, Zed couldn’t actually be sure how high he was. For all he knew, Jacobs’s twisted body was a short distance below, just out of reach of his headlamp.

  A little yellow light blinked on in the corner of Zed’s CIG overlay for the suit's heads-up display. It was the abnormal oxygen consumption warning. With great mental effort, Zed slowed his breathing and tried to focus on the ladder rung directly in front of his face.

  “Uh, Douglas, you there?”

  Douglas was programmed to appear on a surface in front of Zed’s field of view. The only surface available was the case dangling below. Zed laughed when the little cartoon spaceman popped into existence, balancing on the edge of the case and frantically waving his arms as if making a great effort not to fall.

  “Douglas, play something from my audio comfort food list. Maybe some ‘X Minus One’ or something.”

  There was a pause, and then a crackle of a radio recording more than a century old.

  “Countdown for blast-off. X minus five, four, three, two. X minus one. Fire,” the announcer said in a serious old-time radio voice.

  What was it about radio voices in the nineteen-fifties? Did they just go find people who sounded like that?

  “From the far horizons of the unknown come transcribed tales of new dimensions in time and space. These are stories of the future, adventures in which you'll live in a million could-be years on a thousand maybe worlds.”

  Zed had heard this intro more times than he could count, and something about the familiarity brought the world back into focus.

  He brought a searching toe forward, found the next rung, and continued to push himself onward.

  It might have only been a few minutes before the far wall of the crevice came into view, but it felt like an eternity. Once he reached the edge, Zed hoisted the sample case up and shoved it onto the rock ledge. He then proceeded to pull and push himself forward until he ran out of ladder rungs to push off from.

  Zed raised his head with care until the back of his helmet bumped against the low ceiling. It was claustrophobic, to be sure, but he still had enough room to maneuver on hands and knees now that he wasn’t dangling over the bottomless pit.

  Sample case back in hand, he continued forward, back on the hunt for holographic blue dots.

  Eventually, the ceiling rose enough that Zed could stop crawling. He was grateful, though he had to wonder if the pain in his back was going to be with him forever.

  The episode of “X Minus One” that Douglas had started finished, and another began. It occurred to Zed that what he was doing right now would have made a pretty good episode of that show. Maybe he’d look back on this as just that sort of adventure. Maybe, but first he had to actually find something and survive. And then, most likely, he’d have to face the wrath of his parents and every other authority figure on the planet.

  In truth, I’ve already made it further than anyone else managed, Zed thought. So screw ‘em.

  Time passed. Maybe hours. Maybe minutes. Zed wasn’t sure anymore. Crawl. Walk. Rinse and repeat.

  He locked his exoskeleton legs and rested against a rough wall, willing himself to look down the passage ahead, hoping that the endless blue dots wouldn’t dip under another low ceiling.

  To Zed’s surprise, a mere dozen blue orbs stretched out to his left, where the line came to an abrupt stop. The tunnel continued on, but the markers did not. Zed had a brief moment of confusion, quickly followed by a burst of excitement. He pushed himself off the wall, eyes glued to the final marker.

  Zed once a friend in the online 3D art community who had been deep into character animation—something Zed had little talent for. She had once told him that to animate a walk, you had to understand that it was just a continuous series of controlled falls. You tip yourself forward and then catch yourself. You just repeat that until you get where you’re going. That was all Zed could think of as he attempted to move his right leg forward to start his walk and control his fall, only to realize he’d forgotten to unlock the exoskeleton legs.

  Zed face-planted onto the floor of the lava tube. He smelled blood as his nose smashed against the face shield, which thankfully did not crack or shatter. After lying there a moment, catching his breath and clearing his head, Zed reached down to his right hip and then his left, unlocking the exoskeleton. He reached for a handhold on the nearby wall and pulled himself up with care.

  What is it about getting hurt that makes it impossible to tell if you’re actually injured?

  Zed could feel that his nose was bleeding, but aside from that, he seemed okay. He hoped the bleeding would stop on its own. If it didn’t, there wasn’t much he could do about it. It wasn’t exactly possible to flip his helmet shield and stuff cotton balls up his nostrils without, you know, dying.

  I’m gonna get myself killed before Mars even has a chance, Zed thought, sniffing up blood and willing it to clot.

  This wasn’t even the hard part. That was waiting for him where the blue dots vanished.

  “I must be out of my mind,” Zed whispered to the empty dark as he stood there, staring at the small hole that looked far smaller in person than it ever had in any virtual representation he’d seen.

  Standing here now only confirmed what he knew from the start. There was no way a human in a turtle suit could fit through the hole. At least, there was no way to fit through with a pack on.

  The trouble was that the pack contained a few important things, chief of which was life support.

  “This was a terrible idea.”

  The feeling Zed got from looking at that tiny opening was far worse than gazing into the dark hole where Jacob had met his end. He thought of the sudden claustrophobia he’d experienced the first time he tried to crawl into a turtle suit and felt that same sensation crawling hand over fist down his spine.

  At the same time, he knew there was zero chance of him turning back. He was committed now. After the struggle he’d gone through to get here, turning away without even trying was not an option.

  He was going to have to be quick. It wasn’t so much the lack of oxygen as the buildup of CO2 that would get him first. It would come down to how long he could hold his breath, which would depend on how much exertion it would take to crawl through the passage.

  Lying on his bed, he’d managed to hold his breath for 2 minutes, but that was without a pounding heart and physical exertion. He wasn’t sure how much time he’d likely have, but it would probably only be a minute before he couldn’t hold it in any longer and started to pollute his suit with every breath.

  Zed knelt down and looked into the narrow entry. The shadows cast by his headlamps made it difficult to get a good look. He reached into one of his chest pockets and removed a couple of glow sticks. Giving each a quick bend and shake, he tossed them down the tunnel.

  He tried to land each in a different position, spacing them out down the length of the passage. He could just make out the tunnel’s end, but there was nothing beyond but blackness. Seeing that there was, in fact, an end made him feel at least a little better.

  Still, he had no guarantees of how much space he’d actually have on the other side. If it wasn’t enough room to get his pack back on, then making it through would be a short-lived victory.

  The clock was ticking, and staring at the problem before him wasn’t going to change the fact that he would have to cut himself off from his life support and crawl through a dark, dangerous tunnel while holding his breath and praying he didn’t get stuck.

  Zed spent the next few minutes practicing disconnecting from the turtle pack, taking it fully off, putting it back on, and then reconnecting it. That procedure alone took at least a minute at best. Not good. That wasn’t going to leave him much time. There was no room for error. No time for hesitation. Getting caught on an outcropping while in the crawl space would be deadly.

  For the first time, Zed’s confidence in his plan faltered. This was real. He could actually die down here, and no one would ever know.

  “Stop it!” Zed shouted into the dark. There was no point in psyching himself out now.

  Zed knelt in front of the passage and strapped the sample case to his ankle so that he could drag it through behind him. As his heart rate slowed, he started taking deeper breaths, flooding his blood with oxygen. He exhaled deeply, took in one more lungful, and began the process of disconnecting his life support.

  The moment the procedure was finished, he dropped the pack in front of him and gave it a shove into the passage. As gracefully as he could manage, Zed laid down on his stomach and pulled himself in after it.

  Instantly, one thing became painfully apparent. For all his careful planning, Zed had overlooked the fact that the moment he laid down, he could no longer see in front of him. The helmet wasn’t designed to have enough mobility to look straight up, and the glass of the faceplate only offered a view to the front and a little to the sides. He was going to have to do this entirely by feel.

  There was no time to dwell on it. Time was already running out. Zed reached his arms up and shoved the pack forward a few more feet, being careful to keep it straight in hopes of avoiding any rocks that might be sticking out. Zed tried to get into a push-up position to lift his body and slide it forward, only to have his elbows slam into the ceiling. There wasn’t enough room to lift himself. He was going to have to drag himself through.

  Zed’s lungs were starting to burn. He could feel the pressure of holding his breath building in his head, and he was only a few meters in. Pushing that thought aside, he started to drag his body forward, reaching his hands above his head to use the ridges on the ground as a horizontal ladder. Every time he felt the turtle pack bump into the top of his helmet, he would reach up and give it a careful shove.

  He wasn’t sure how far he’d moved down the passage. It felt like he should have been through by now. He reached his arm toward his back. He could still feel the oppressive ceiling just above him. He wasn’t going to last much longer.

  Zed scrambled forward now, halfway to panic. He didn’t bother to shove the pack ahead; he just let his helmet push it forward in his wake. His burning lungs exhaled into the suit with an outpouring of spent air. He inhaled deeply. He couldn’t help it. His head felt fuzzy now. Everything burned. He scrambled a few more feet, and then, without checking above, he tried to rise to his knees. To his great relief, he was able to do just that. Too slowly, Zed realized he was free. He spent precious seconds in surprise, and then, with the last of the clarity and energy he could muster, he grabbed at the pack, trying not to fumble the reconnection.

  Zed came to lying face down in front of the passage. In a moment of panic, he reached behind him and felt the turtle pack. He breathed a sigh of relief and realized that the air he was breathing wasn’t burning his lungs.

  How long have I been out? he wondered. It felt like ages, but a glance at the clock told him it had been only a minute or two.

  Then he remembered. He’d been in such a rush to get the pack connected that once he had, and the fresh air started flowing in, he’d hyperventilated and knocked himself out.

  Maybe he’d just leave that particular detail out when retelling this story.

  “I made it!” Zed breathed, rising to his feet with care. His lights had turned off, and all he could see was the little green pool cast by one of the glow sticks he had thrown in earlier.

  Zed hesitated before turning on his headlamps. What if there was nothing here? What if he’d risked his life for nothing, and this was just another empty cavern with some cool rocks?

  Zed flipped the switch and turned toward the open chamber.