Ralph stepped back. “Tarantulas.”

“Albino tarantulas,” Maggie moaned.

The army continued its scurried march. Scouts skittered to either side of the boulder. A few paused where the rock was damp and steamed slightly from Norman’s morning relief, clearly drawn to the warmth.

“It’s our body heat,” Sam said. “The damned things must be blind and drawn by noise and warmth.”

Behind him, Denal started gibbering in his native Quecha.

Sam swung around. The young Indian was gesturing in the opposite direction, toward the far side of the gold path. Norman turned his flashlight to where Denal pointed. As another flank of the army streamed down the other wall on pale, hairy legs, Sam suddenly had an awful sensation crawl up his back.

Sam arched his neck, raising his lantern high.

Overhead, the roof was draped by a mass of roiling bodies, crawling, mating, fighting. Thousands of pendulous egg sacs hung in ropy wombs of silk. The students had stumbled into the main nest of the tarantulas… and the army of predators was hunting for prey. They were already moving down the pillars, as if the carved figures were giving birth to them.

The group scattered from under the shadow of the monstrosity, fleeing back to their campsite.

As they retreated, Sam studied the huge spiders. Dependent upon the meager resources found in these caves, the tarantulas had clearly evolved a more aggressive posture. Instead of waiting for prey to fall into webs, these normally solitary spiders had adapted a more cooperative strategy. By massing together, they could comb the caves more successively for any potential sources of a blood meal, taking down larger prey by their sheer numbers—and Sam had no intention of being their next course.

“Okay, folks, I think we’ve overstayed our welcome,” he said. “Gather our gear and let’s get the hell out of Dodge.”

“Where to?” Maggie asked.

“There’s a path through these caves, right? Those Indians who forged it must have done so for a reason. Maybe it’s a way out. Anyone object to finding out?”

No one did. Five sets of eyes were still on the encroaching tarantulas.

Sam slipped the gold dagger into his vest and collected his grandfather’s rifle. He gestured to the others to collect their few possessions. “One flashlight only,” he said, as he led the way down the path. “Conserve the other. I don’t want to run out of illumination down here.” A shiver passed through Sam at the mere thought of being trapped, blind, with a pale army of poisonous predators encircling him. He tightened his grip on his rifle but knew it would do him little good if the lights went out.

Norman followed with the flashlight, glancing frequently behind him.

“As long as we keep moving, the spiders won’t get you, Norman,” Ralph said with a scowl.

The photographer still kept an eye on their backtrail. “Just remind me… no more bathroom breaks. Not until I see the light of day.”

Sam ignored their nervous chatter. It was not what lay behind them that kept Sam’s nerves taut as bowstrings, but the trail ahead. Just where in the hell would this path take them?

Unfortunately there was only one way to find out.

As they proceeded, Norman mumbled behind him. “Lions and tigers and bears, oh my…”

Sam glanced back, his brow furrowed in confusion.

Norman nodded to the gold path. “Sort of reminds me of the yellow brick road.”

“Great,” Ralph groused. “Now the fruit thinks he’s Dorothy.”

“I wish I was. Right now I wouldn’t mind a pair of ruby slippers to whisk me home,” Norman grumbled. “Or even back to a farm in Kansas.”

Sam rolled his eyes and continued onward.

The remainder of the long morning stretched into an endless hike, mostly at a steady incline. Legs and backs protested as the cavern system led them higher inside the Andean mountain. If not for the lack of food and the growing exhaustion, Sam might have better appreciated the sights: towering stalagmites, cavernous chambers with limpid pools that glowed with a soft phosphorescence, cataracts that misted the gold trail at times with a welcome cooling spray, even a side cave so festooned with lacy crystals that it looked as if the chamber was full of cotton candy. It was a wonderland of natural beauty.

And everywhere they went, the carved pillars marked their way as grim sentinels, watching the group pass with unblinking silver eyes.

But as amazing as the sights were, the memory of what lay behind them never fully vanished. Breaks to drink from the stream were often accompanied by worried glances toward the rear. So far there had been no sign of pursuit by the tarantula army. It seemed they had left the spiders far behind.

Slowly, the morning wound to afternoon. The only highlight was a brief lunch to split a pair of Milky Way bars found stashed in Norman’s camera case. Chocolate had never tasted so good. But even this small taste of heaven was short-lived, and only succeeded in amplifying everyone’s hunger. Tempers began to grow short and attitudes sullen as they marched through the afternoon.

To make matters worse, a sharp pungency began to fill the cavern’s normally crisp air. Noses wrinkled. “Ammonia. Smells like the ass end of a skunk,” Sam commented.

“Maybe the air is going bad,” Norman said with a worried expression on his haggard face.

“Don’t be a fool,” Ralph snapped. “The air would have been worse when we were deeper.”

“Not necessarily,” Maggie said. Her eyes had narrowed suspiciously, squinting at the darkness beyond the light. “Not if there was a source giving off the noxious fumes.”

Ralph still scowled, clearly tired and irritated. “What do you mean?”

Instead of answering, Maggie turned to Sam. “All those tarantulas. From the look of them, they were well fed. What do the feckin’ things eat down here?”

Sam shook his head. He had no answer.

“Oh God!” This came from Norman, who had taken the lead with the flashlight. The gold path led over a short rise into a neighboring cavern. From the echo of his exclamation, the chamber was large.

The others hurried to join him.

Maggie stared at the scene ahead, holding a hand over her mouth and nose. The sting burned their eyes and noses. “There’s the answer. The source of the tarantulas’ diet.”

Sam groaned. “Bats.”

Across the roof of the next cave, thousands of black and brown bats hung from latched toes, wings tight to bodies. The juveniles, squirming among the adults, were a paler shade, almost a coppery hue. Sharp squeaks and subsonic screeches spread the warning of intruders across the legion of winged vermin. Hundreds dropped from their perches to take flight, skirting through the air.

The source of the odor was immediately clear.

“Shit,” Ralph swore.

“Exactly,” Norman commented sullenly. “Bat shit.”

The floor of the cavern was thick with it. Carved pillars, fouled with excrement, speared upward through the odorous mess. The reek from the aged droppings was thick enough to drive them all back with a stinging slap.

Norman tumbled away, choking and spitting. Bent at the waist, he leaned on his knees, gagging.

Ralph looked as if his dark skin had been bleached by the corrosive exposure. “We can’t cross here,” he said. “We’d be dead before we reached the other side.”

“Not without gas masks,” Maggie agreed.

Sam was not going to argue. He could barely see, his eyes were watering so fiercely. “Wh… what are we going to do then?”

Denal spoke up. He had hung back from the cavern’s opening and so had borne the least of the exposure. Even now, he was not facing ahead, but behind. He had an arm pointed. “They come again.”

Sam turned, blinking away the last of the burn. He took the flashlight from the incapacitated Norman. Several yards down the gold trail, three or four white bodies scurried across the rocky landscape. Scouts of the tarantula army.

“To hell with this,” Ralph said, voicing all their concerns.

“What now?” Maggie asked.

Sam glanced forward and backward. Everyone began talking at once. Sam raised the light to get everyone’s attention. “Stay calm! It won’t do us any good to panic!”

At that moment, Sam’s flashlight flickered and died. Darkness swallowed them up, a blackness so deep it seemed as if the world had completely vanished. Voices immediately dropped silent.

After a long held breath, Norman spoke from the darkness. “Okay, now can we panic?”

Joan ushered Henry into her lab. “Please make yourself at home,” she offered, then glanced at her wristwatch. “Dr. Kirkpatrick should be here at noon.”

Behind her, Henry had paused in the dooway to her suite of labs, his eyes wide. “It’s like a big toy store in here. You’ve done well since our years at Rice.”

She hid a smile of satisfaction.

Slowly, Henry wandered further into the laboratory, his gaze drifting over the plethora of equipment. Various diagnostic and research devices lined the back of the room: ultracentrifuge, hematology and chemistry analyzer, mass spectrograph, chromatograph, a gene sequencer. Along one wall was a safety hood for handling hazardous substances; along the other stood cabinets, incubators, and a huge refrigerated unit.

Henry walked along the row of machines and glanced into a neighboring room. “My God, you even have your own electron microscope.” Henry rolled his eyes at her. “To book any time on our university’s, it takes at least a week’s notice.”

“No need for that here. Today, my lab is at your full disposal.”

Henry crossed to a central U-shaped worktable and set down his leather briefcase, his eyes still drifting appreciatively around the room. “I’ve had dreams like this…”

Chuckling to herself, Joan stepped to a locked stainless-steel cabinet, keyed it open and, with two hands, extracted a large beaker. “Here’s all the material we collected from the walls and floor of the radiology lab.”

She saw Henry’s eyes widen as she placed the jar before him. He leaned over a bit, pushing his glasses higher on his nose. “I didn’t realize there was so much,” he said. The yellowish substance filled half of the liter-sized beaker. It shone brightly under the room’s fluorescent lights.