The team did not even have time to do anything more for Frank. They could only leave a fluorescent marker nearby before abandoning the corner as quickly as possible.
Following Leah's team's footprints and the disturbing drag marks, they rushed toward the workshop's upper levels and deeper into the facility.
After traveling a little farther, Maya suddenly lowered her voice and aimed her flashlight at the shadows around a pipe joint.
"Calista, look over there!"
A fist-sized metal canister had been secured to the pipe with heavy-duty tape. A red indicator light flashed slowly on its surface, while a faint white aerosol, almost invisible to the naked eye, continued spraying from its nozzle.
Bossie moved closer to examine it.
"It's a chemical neutralizer detonator installed by the Spearhead Task Force. This one has already discharged."
He scanned the air with a portable detector. Thanks to the rescue team's old anti-electromagnetic interference equipment, their instruments had not yet failed completely.
"The nerve agent concentration has dropped by more than seventy percent in this area. The task force is creating a relatively safe corridor. But the neutralizer's coverage is limited, so we need to follow their exact route."
As they continued upward, the rescue team discovered two more identical detonators, each cleverly positioned at a key point in the airflow.
Leah's team's route was now clear.
They had not been wandering blindly. Even in such an extremely dangerous environment, they were still using their limited resources to carve out a path to safety while continuing their mission.
The realization calmed the anxiety that had gripped Calista since the deaths of Anderson and Frank Wilson.
Leah and the others were still alive.
They were still fighting.
Then they heard it.
"Rat-tat-tat... Bang! Rat-tat..."
Faint bursts of automatic rifle fire echoed from somewhere far above them. The sound was distant, but unmistakable.
Gunfire!
It was Leah's team.
They were alive!
They were somewhere above, engaged in combat.
"Move!" Calista ordered.
The squad instinctively quickened its pace, nearly breaking into a run up the steel stairs.
The gunfire above was intermittent rather than intense. It sounded more like precise suppressive fire or a brief skirmish, but it was enough to prove that Leah's team was still resisting.
Just as they were about to turn onto a zigzagging suspended walkway, two heavy impacts erupted from the metal platform two levels below.
"Thud! Boom!"
The entire steel framework beneath their feet trembled. Dust and flakes of rust rained down around them.
Everyone froze, then turned their weapons toward the stairs behind them.
Two figures slowly emerged through the cloud of dust.
Both moved on all fours, their bodies tall and powerfully built.
The creature on the left was the wounded Predator that had escaped earlier.
The grooves in its tumor where Calista's bullets had struck were still leaking black-green neural fluid. Yet its posture now radiated a vicious, agitated fury. Its spindle-shaped tumor remained fixed on Calista as it emitted a rapid series of shrill clicking sounds.
The creature beside it was nearly a full size larger.
Its brown crystalline armor was much thicker. Its crystalline bone blades were longer and more robust, with faint serrations running along their edges.
Most disturbing of all, several short, sharp crystalline spikes protruded from the tip of its spindle-shaped tumor, making it appear even more ferocious than the first Predator.
It shifted slightly to the side. The grooves across its tumor opened and closed as though it were receiving information from its companion.
Then its massive body slowly turned toward Calista's squad.
"So it called in its big brother," Calista said coldly. "Looks like we hurt the little one, and the big one came looking for revenge. These damned things can even hold a grudge."
"They've blocked our retreat," Bossie quickly assessed. "Our only option is to keep going up and rendezvous with Leah's team."
Before he had even finished speaking, the larger Predator moved.
It did not immediately leap at them. Instead, it dropped onto all fours and charged, heading straight for Calista at the front of the formation.
The smaller Predator scrambled onto the pipes along the wall, attempting to coordinate with its companion and attack from the flank.
"Cover each other and fall back upward! Maya, Ethan, Bossie, suppress the one on the pipes! Jenson, Mikey, Leon, help me hold off the big one! Honeywell, get upstairs first!"
As Calista issued her orders, she raised her rifle and aimed at the larger Predator racing toward them.
"Bang! Bang! Bang!"
Bullets hammered into its thick brown crystalline armor. Most ricocheted away, while the rest left only shallow white marks and hairline cracks.
None penetrated.
The creature did not slow at all.
In the blink of an eye, it had crossed most of the distance. One of its forelimbs swept toward them, the crystalline bone blade slicing through the air with a piercing whistle.
"Move!"
Calista, Jenson, Mikey, and Leon threw themselves aside.
The bone blade passed close enough to scrape across Leon's back, nearly knocking the oxygen tank from his harness.
Jenson seized the opening and fired at the side of the larger Predator's seemingly vulnerable knee joint.
"Clang!"
The bullet struck a protruding crystal and ricocheted away.
"ROAR!"
Enraged, the larger Predator abandoned Calista. It spun around and swung its claw at Jenson.
Above them, Maya and the others temporarily pinned down the smaller Predator as it tried to leap from the pipes. Bullets struck the metal around it, showering sparks and forcing the creature to dodge repeatedly.
"Use a stun grenade!" Calista shouted.
She scrambled to her feet and saw the larger Predator turn its back toward the stairs as it attacked Jenson.
This was their chance.
Mikey gritted his teeth, pulled out a stun grenade, held it for two seconds, then rolled it precisely beneath the Predator's hind legs.
"BOOM!"
A deafening blast and blinding flash filled the walkway.
The larger Predator's thick crystalline armor seemed to reduce the effects of the sound and light, but its enormous body still shuddered visibly. Its movements stiffened, and it stumbled off balance.
"Aim for the base of the tumor! The armor may be thinner there!"
Calista emptied her rifle into the area beneath the repulsive black-purple tumor.
"Pfft! Pfft! Pfft!"
Several bullets finally punched through, spraying a small burst of black-green fluid.
The larger Predator unleashed a deafening roar and staggered backward. Its massive body slammed into the steel railing, bending and twisting it out of shape.
It thrashed its tumor violently, clearly suffering significant damage to its nervous system.
"Now! Fall back upstairs! Move!"
Calista had no intention of prolonging the battle. The Predator's armor and vitality far exceeded their expectations.
Using the brief opening, the squad scrambled up the suspended walkway as fast as they could.
The Predators recovered quickly and raced after them.
On the narrow walkway, Calista's team had no chance of outrunning two Predators sprinting at full speed on all fours.
Their escape route was completely cut off.
"Damn it! There's nowhere left to run!" Calista shouted. "We finish them here!"