The roller door of the underground garage was mottled with rust, as if half-welded shut by time.
Chen Mo swung the fire axe down at the narrow gap. Sparks burst in the dark; the metal shriek echoed in the enclosed space, drilling into their eardrums like steel needles. Su Xiaoxiao's ultraviolet lamp cast a slanting beam through the crack, illuminating floating dust—and a slow trickle of liquid that gleamed oily red in the beam.
"Engine oil."
Chen Mo's combat boot slammed into the door. Rust powder fell in a soft cascade. "There's a car inside. Someone drove it in recently."
"Shadow," the cat, suddenly arched its back and hissed at the gap. Its lame leg trembled, yet it hooked a key toward Su Xiaoxiao's feet—the handle etched with tiny letters: B7.
When the roller door was pried open just enough for a person to slip through, a familiar scent rushed into Chen Mo's nose—mint cigarettes. The scent of the border camp three years ago, when the old company commander always had one between his lips by the campfire.
"Who's out there?"
A hoarse male voice came from inside, guarded and shaking. "Did Nurse Li send you? She told me to hide at parking space B7!"
The UV beam reached into the garage's depths. A military-green off-road vehicle sat there, riddled with bullet holes, its windshield fractured like a spider's web. In the driver's seat, a silhouette gripped something metallic—a military dagger.
"Drop the weapon." Chen Mo leveled the fire axe. "Nurse Li is dead—killed by her own shadow."
The silhouette flinched, the dagger clattering to the floor. The light revealed a face—Yang Peng, the old commander's bodyguard. He had lost a leg in a mine-clearing mission three years ago; by rights, he should have been long discharged.
"She… died?"
Yang Peng's voice was like paper soaked in water. "Just yesterday, she told me over the radio she'd found a way to suppress the shadows…"
Su Xiaoxiao saw his empty trouser leg; the bandages seeped with a bluish-black stain—the color of early infection. Yet in the lamplight his shadow was sharp and intact, even showing the missing leg.
"You've been infected?" Chen Mo probed.
Yang Peng suddenly cut open the skin of his thigh. Bright red blood welled out.
"Nurse Li used her serum to save me. The cost was—" He pointed to his missing leg. "It started rejecting me, like it had a mind of its own."
Chen Mo's gaze drifted to the SUV's rear compartment, stacked with sealed crates labeled Emergency Vaccine, serial numbers matching those from Project Crimson. Lin Lan's notes had said the early vaccines could suppress the virus but often caused tissue necrosis.
"These vaccines…"
"Stolen from the research facility in the east side of the city," Yang Peng replied. "Professor Wang keeps shadow thralls there—humans fully controlled by their shadows. No pain, impervious to bullets and blades, harmed only by ultraviolet light."
Su Xiaoxiao remembered the sketch in her father's notebook—a human figure wrapped in blackness, red letters marking: Host consciousness consumed. Highest danger level.
Yang Peng lowered his voice. "Nurse Li said the thralls' shadows hold primordial matter—the virus's core. Extract it, and you can make a true cure. She told me to wait for two 'clean' people to come for it."
"Clean people?" Chen Mo glanced down at his own shadow—resting quietly in the red glow.
"Unaffected by shadow contamination."
Yang Peng lifted his shirt, revealing a pale blue birthmark on his chest in the shape of a butterfly with spread wings. "Nurse Li said natural immune hosts have this mark. They can purify the primordial matter."
Instinctively, Su Xiaoxiao touched the back of her neck—where the same mark lay. Her father had said it was inherited from her mother. In that moment, she understood why he had left his notes to her, and why Lin Lan had repeated mentions of the "butterfly mark." Chen Mo had noticed her gesture as well.
A metallic clang came from deep in the garage. "Shadow" the cat bristled, its lame leg bleeding, drops spattering the ground.
"They're here." Yang Peng's voice was low. He shoved the fire axe under the car. "Shadow thralls. Better hearing than dogs. Hide—now."
Su Xiaoxiao slid under the vehicle, inhaling the sharp tang of disinfectant. A note was taped to the undercarriage—Nurse Li's handwriting:
The primordial matter lies in the thrall's heart. UV light will reveal it, but drive it into frenzy. Yang Peng is infected—do not fully trust him.
Footsteps approached—uniform, heavy, unnervingly mechanical. Through the gap, the thralls wore black combat gear, silver masks hiding white, pupil-less eyes. Their rifles were bound in black cloth, muzzles silent.
"Found parking space B7," one thrall's voice was cold as synthetic speech. "Activate thermal imaging."
Suddenly, Yang Peng rolled from the other side of the car, Molotov in hand. "Over here! Come get me!"
The thralls turned toward him in unison. Chen Mo yanked Su Xiaoxiao out; the UV beam hit the nearest thrall's head. A scream tore the air; black fluid oozed from under the mask, dripping into a warped human silhouette.
"Its shadow is in the car!" Su Xiaoxiao shouted, pointing her blade at the SUV.
Chen Mo kicked in the window. Inside, the thrall's shadow writhed, its movements slowing. Under UV, black liquid erupted; its uniform burned through to reveal bluish-black skin.
Yang Peng's Molotov burst among the thralls, a wall of fire roaring upward. The stench of char filled the air. They ignored the flames, advancing through them.
"Get in!" Chen Mo barked. Su Xiaoxiao jammed the UV lamp into the rear seat, its beam bouncing off the rearview mirror like a blade across their eyes, stunning them briefly.
"The crimson cross on their chests—it's the same as the tags on Professor Wang's virus samples," Su Xiaoxiao's voice shook.
"His private army."
The radio crackled—Lin Lan's broken voice: "…the thralls' primordial matter fears sound waves… 120 decibels… will make them—"
Gunfire cut her off.
"Horn—now!" Chen Mo slammed the accelerator. The SUV roared; the blaring horn shook dust from the ceiling. The thralls clutched their heads, black fluid boiling, chests bursting open as black shadows shot out, shrinking under UV into a single black bead.
"It's the primordial matter!" Su Xiaoxiao lunged for it—but Yang Peng snatched it from her.
Chen Mo saw it then—Yang Peng's shadow had already slipped from his body in the horn's vibration, slithering toward Su Xiaoxiao. The butterfly mark on his chest glowed red in the firelight—not a birthmark, but a painted sigil of viral fluid.
"You're not Yang Peng," Chen Mo said coldly. "The real Yang Peng died at the border—I attended his funeral."
Under UV, the imposter's face rotted away, revealing a metallic skeleton. "Hand over the primordial matter, and I'll let your shadow die quickly."
Su Xiaoxiao crushed the black bead—icy liquid seeping into her palm. Her shadow screamed, but in the golden glow it sharpened, its edges haloed with light. Nurse Li's note flashed in her mind:
Primordial matter loses effect in the blood of a natural immune host, and purifies the shadow.
The false Yang Peng's shadow turned to ash in the golden light; his body collapsed into scrap, leaving only white, pupil-less eyes staring at Su Xiaoxiao.
Her UV beam fell on a black case beneath the B7 tiles—inside, a portable ultrasonic emitter, a photo of Yang Peng and Nurse Li tucked beside it. She wore a butterfly brooch, smiling brightly.
"They were lovers," Su Xiaoxiao murmured. "She knew the risk, but still saved him."
"Shadow" the cat batted the emitter's switch. In the red light of the garage entrance, countless shadows surged like a tide.
"Their true bodies are here," Chen Mo said, turning the device to full power. "One-twenty decibels works on thralls. Let's see if it works on them."
Su Xiaoxiao gazed at the photo, remembering the last line in her father's notes:
The light of humanity is not in never being betrayed, but in choosing to trust even knowing betrayal is possible.
The ultrasonic shriek split the dark. They fled up the stairwell toward the surface.
Behind them, the butterfly brooch at B7 glinted in the red light, as if watching the backs of two "clean" ones chosen by fate.