The wooden stairs groaned drily under Lu Chenzhou's feet. Morning light slanted in through the glass door of the "Zhi Zhi Zhai" bookstore, cutting a pale, bright streak through the floating dust. He pushed the door open, and the old doorbell let out a hoarse, drawn-out groan. On the street, the greasy smoke from breakfast stalls mixed with the damp morning air rushed in. The city's sounds, like a tide, instantly swallowed the stale odor of old paper and dust from the bookstore behind him. He didn't stop, turning directly into the narrow alley beside the shop, cluttered with trash bins. Deep in the alley, a slightly worn grey minivan sat with its engine off, parked quietly beside a puddle. The side door was pulled open a crack from the inside. Lu Chenzhou slipped in sideways, and the door closed immediately. The interior of the van was thick with the smell of sweat, engine oil, and the sour stench of leftover food. Three men were crowded in the gloom, none of them speaking. The driver was a middle-aged man with a crew cut and a thick neck, his knuckles large and coarse. He was unconsciously rubbing a cheap imitation gold pendant on a chain—Old Wu. In the middle seat was a skinny man with black-rimmed glasses, a tablet computer open on his knees. The screen's ghostly light illuminated his tense jaw—Glasses. Crouched in the shadows of the back row was another, his face unclear, only the sound of heavy, suppressed breathing could be heard, once, then again. "Drive," Lu Chenzhou said. His voice sounded flat and even in the enclosed space, devoid of inflection. Old Wu turned the key. The engine growled to life, and the minivan slowly slid out of the narrow alley, merging into the sluggish traffic of the morning rush hour. Lu Chenzhou took out a waterproof paper folded into a square from inside his coat and unfolded it. On it was a hand-drawn schematic in pencil, the lines precise, marked with angles and distances. He tapped his index finger on several turning points, his nail scraping lightly against the paper with a faint rustling sound. "The boiler room entrance is here," he began, his pace deliberate, each word measured as if with a ruler. "Diameter sixty-eight centimeters. Seventeen meters in, the first right-angle bend." He paused for half a second, letting the information sink in. "Risk of rust collapse on the inner side of the bend. Must stay close to the outer wall when passing through, lean body weight fifteen degrees to the left." Glasses glanced at him in the rearview mirror, his lips moving slightly, but no sound came out. "Questions? Ask them now," Lu Chenzhou said without looking up, his gaze still fixed on the schematic. "The data..." Glasses's voice was a bit dry. He cleared his throat. "This diagram is a reproduction of an old blueprint. Twenty years old. The internal structure of the pipe, the degree of corrosion, load-bearing... we haven't done an actual scan." He pushed his glasses up the bridge of his nose. "An error of over five centimeters, and a person could get stuck inside. Permanently stuck." Lu Chenzhou folded the schematic and raised his eyes. His gaze swept over the other two silent faces in the dim van, finally landing on the reflective lenses of Glasses's spectacles. "The error exists," he acknowledged, his tone devoid of emotion. "That's why we need to pass through the most dangerous first thirty meters within seven minutes. After seven minutes, the main gate in Zone A3 will close. The main assault team arranged by Gu Zhixing will trigger the explosive traps near the load-bearing wall." He paused, a barely perceptible twitch at the corner of his left eye. "The blast wave and collapse will completely seal that route, and will also collapse the section of pipe above our heads." He repeated the annotation on the schematic, word by deliberate word: "The data is on the wall. The risk is overhead. The choice is in your hands—get out now, or go in." Old Wu's hands tightened on the steering wheel, his knuckles turning white. His Adam's apple bobbed. "My son's birthday is next month," he muttered gruffly. The statement seemed out of nowhere, but the other two men in the van understood. He needed the money, needed the reward for surviving this job. His stubby fingers clenched the pendant in his palm. From the shadows in the back row came a heavy exhalation, as if a decision had been made. Glasses pushed his glasses up again, his fingers swiping quickly across the tablet screen. The ghostly light flickered, illuminating his taut mouth. "Captain Qin's signal... just updated. Passage cleared. Time: seven minutes." His voice dropped even lower, almost a whisper. " The interior was more spacious than expected, piled high with discarded metal parts and shattered concrete blocks. The only light came from a few grimy skylights high above, casting several dim yellow beams through which dust slowly tumbled. On the wall directly facing the entrance, a circular opening less than seventy centimeters in diameter gaped open, its edges jagged with rusted metal, like the silent maw of a giant. Below the opening, the ground was covered in a thick layer of dark gray dust, mixed with unidentifiable debris. Lu Chenzhou walked to the opening, crouched down, and pulled a laser pointer from his backpack. A crimson dot of light struck the mottled concrete wall opposite, trembling slightly before finally settling on a blurred, spray-painted graffitied old mark on the wall. “Entrance,” he said, switching off the laser pointer and standing up. He began removing his outer jacket, revealing a dark gray, close-fitting work suit with reinforced elbows and knees. He put on fingerless tactical gloves, checked his headlamp and the dim LED light on his forehead, and finally slid a small sealed bag and a dagger into the quick-draw holster on his leg. The metal buckle clicked softly. Old Wu and Glasses silently made the same preparations. The team member who had remained silent in the back—a burly man with a scar on his face, nicknamed “Anvil”—dragged a heavy toolkit from the vehicle compartment. Hydraulic cutters, folding saws, and several rolls of emergency support rods clanked together, emitting a dull metallic scraping sound. “Order,” Lu Chenzhou’s voice echoed slightly in the empty boiler room. “Me, Glasses, Anvil, Old Wu takes the rear. Maintain silence once inside. Communication channel is only for reporting obstacles and positions.” His gaze swept over the three of them. “Oxygen is limited. Control your breathing.” He paused. “If you get stuck, don’t struggle. Report your position and wait for rescue. If the pipe collapses…” He didn’t finish, but the meaning was clear. He was the first to turn, facing the dark opening. He placed his hands on the cold, rough edge, took a deep breath—the air thick with the gritty feel of rust and dust—then curled his body and crawled inside. His body was instantly enveloped. Cold, rough, rusted metal walls pressed tightly against his shoulders, back, and thighs. The space was so narrow he could only rely on alternating pushes from his elbows and knees, inching forward like some degenerate reptile. The beam from his headlamp carved out a limited field of vision in the absolute darkness, illuminating less than two meters ahead: the circular inner wall of the pipe was covered in dark red rust nodules and flaking paint, with dark, damp stains seeping through in places, their composition unknown. The air was stagnant, heavy with the metallic tang of rust and the smell of age-old dust. With every breath, he could feel fine particles scraping against his throat. He turned off his headlamp, activating only the dim LED on his forehead. The faint green light barely outlined the pipe’s contours. It saved power, but also made the surrounding darkness feel heavier and more oppressive. With his right hand, he fished out a glow stick and, feeling his way, attached it to the upper pipe wall, marking the first five-meter point. The sticker emitted a sickly green halo under the faint light. From behind came the soft rustling sounds of friction and suppressed panting. Glasses had followed him in. Then came the grinding, teeth-on-edge sound of metal deforming as Anvil’s heavy frame squeezed into the pipe. Flakes of rust pattered down, getting into Lu Chenzhou’s eyes. He closed them, waiting for the stinging to pass. When he opened them again, red rust powder already clung to his eyelashes. A faint buzz of static came through the comm earpiece, followed by Old Wu’s hushed voice: “All personnel inside. Entrance… has been simply concealed.” “Copy,” Lu Chenzhou whispered in response, continuing forward. The first right-angle bend appeared exactly where the blueprint had indicated. He stopped, listening intently. From deep within the pipe came an extremely faint *click*, like metal expanding or contracting with heat, and a distant, indistinct low hum. He adjusted his body angle, shifting his weight to the left. His shoulder scraped against the cold, slick outer wall of the bend as he inched his way around. At the turn, a large sheet of rusted metal plate had buckled upwards, its edges sharp as blades. He carefully pressed it down with his gloved hand, signaling for those behind to be careful. Past the bend, the pipe ahead began a slight downward incline. His elbows and knees rubbed against the rough inner wall, producing a *shushing* sound. In the confined space, it was amplified "Anvil, hydraulic cutters," Lu Chenzhou commanded. A faint clinking sound of tools being passed came from behind. A few minutes later, Anvil's thick arm struggled forward past Lu Chenzhou's side, the jaws of the hydraulic cutters carefully clamping onto the edge of the foreign mass. Anvil exerted force. A sound like tearing metal, grating on the teeth, rang out. The mass was ripped away, revealing the dark, gaping pipe behind it. An even stronger stench of decay and ammonia wafted out, drilling into their nostrils and clinging to the depths of their throats. "Continue," Lu Chenzhou said. He was the first to crawl past the area streaked with viscous residue. His gloves scraped against the pipe wall, picking up some greasy, translucent remnants. The sensation was skin-crawling. The second marker point. The third. The air was growing thin. The sound of breathing grew heavier in his ears, like a bellows being worked. Sweat soaked through the back of his coveralls, sticking to the cold metal; every movement brought the minute pain of fabric pulling against damp skin. His sense of time blurred in the absolute darkness and oppression, only the faint vibration on his wristwatch signaling the passage of another minute. Ahead, a small, rust-eaten, grid-like crack appeared in the pipe wall. A faint light—not their own—seeped through from outside the crack, casting several distorted, ghostly stripes inside the pipe. The observation point had arrived. Lu Chenzhou signaled a halt. He moved close to the crack, pressing his eye against the cold, rusted iron. Beyond the crack was a larger space, seemingly a gap between equipment layers. About ten meters below, he could make out the outlines of concrete structures and crisscrossing pipes. That was the edge of Zone A3, the designated breakthrough point for the main assault team. Dead silence. Only the faint, distant, dull hum belonging to a large structure, like the breathing of a slumbering behemoth. He raised his wrist, aligning the lens of the miniature camera strapped there with the crack. Seconds ticked by. In his earpiece, there was only the suppressed breathing of his teammates and the heavy thudding of his own heart in his chest. *Thump. Thump. Thump.* Suddenly— At the far edge of his field of view below, near the load-bearing wall of Zone A3, a blinding, incandescent white flash erupted without warning! The light instantly swallowed the concrete outlines, dyeing everything a burning, ghastly white. Immediately after, a roar—muffled, twisted, and stretched by layers of thick structure, yet still deep and thunderous like the bellow of a giant beast—came crashing through! *BOOM——!!!* The shockwave of the explosion, even from this distance and distorted by the pipes, transformed into a tangible vibration that surged along the metal pipe walls like a tidal wave! Lu Chenzhou felt the entire pipe shudder violently, emitting a low, resonant *"hum."* More rust dust and debris rained down from above, nearly obscuring the crack. He gripped a protrusion on the pipe wall tightly, his left hand simultaneously shooting back to accurately cover the mouth of Glasses behind him, who had almost cried out in shock. The glove stifled all sound. The tremors lasted two or three seconds before gradually subsiding. Dust churned slowly in the now-dim light filtering through the crack, like smoke lingering after a funeral. Lu Chenzhou removed his hand and looked through the crack again. Below, the area where the load-bearing wall had been was now shrouded in a churning, dense cloud of gray-white dust. Occasional *"crack"* sounds of concrete fracturing could be heard, followed by the dull thuds of heavy collapses. Within the dust, there were no signs of movement, no screams or calls for help—only the dead, buried echoes of the blast. The camera on his wrist faithfully recorded every frame of the flash, the dust eruption, and the subsequent collapse. "Radio silence," he said into his microphone, his voice colder than metal. "Casualty count. Zero." Only deathly silence, and even heavier, desperately suppressed panting, filled his earpiece. He took one last look at the dust cloud that had swallowed at least five or six lives, then withdrew his gaze. "Proceed," he said, his voice betraying no fluctuation. "Increase speed. We're running out of time." The team began inching forward again. Past the observation point, the pipe straightened out and began a slight upward incline. The end couldn't be far now. But the strange odor in the air grew increasingly pronounced—that ammonia-like pungent smell, mixed with rust and dust, became almost thick enough to make one's throat itch and want to cough. Lu Chenzhou frowned slightly, sweeping the The mark displayed an extremely unsettling texture under the cold light. Translucent, gelatinous, firmly adhered to the metal. He carefully drew a dagger from inside his glove, gently touching the edge of the mark with the tip. *Sss—* An extremely faint sound, like cold water dripping onto red-hot iron. Where the blade tip made contact, the pale yellow mucus slightly dented, emitting a wisp of nearly invisible white smoke with a pungent odor. After the tip was withdrawn, the metal wall beneath the mucus showed a matte texture from slight corrosion, distinctly different from the surrounding rust. Lu Chenzhou’s pupils constricted. He immediately gestured for the team to slowly retreat half a meter back. Then, he pulled a sealed bag from his leg, carefully scraped a small piece of the semi-solidified mucus sample with the dagger, placed it inside the bag, and sealed it. The acrid smell of ammonia mixed with decaying protein faintly seeped through even the sealed bag. "Old Wu," he called softly into the microphone, his voice pressed low. "Here," Old Wu’s reply came immediately, tense. "Take a look at this." Lu Chenzhou carefully passed the sealed bag backward. The plastic rustled. Moments later, a sharp intake of breath came through the headset. "This… this isn’t rats, and it’s not leakage," Old Wu’s voice carried a suppressed professional fear, speeding up. "I’ve seen something similar, in abandoned chemical plant sewers… after high-concentration organic waste liquid leaks, certain alkali-loving anaerobic bacteria multiply massively. Their metabolic byproducts… are corrosive and viscous." He paused, as if searching for the right words. "But that smell wasn’t this strong, and the color wasn’t this… ‘fresh’. This mark… can’t be more than twenty-four hours old. And, judging by the dragging direction and volume…" He lowered his voice almost to a whisper. "That thing is sizable. Might still be ahead." Dead silence filled the pipe. Only the faint, sickeningly viscous sound of the mucus sample shifting in the sealed bag, and the heavy, suppressed breathing of four people. The air grew thinner. Ahead, an unknown biological threat with corrosive properties. Behind, the death trap just triggered. They were in an abandoned metal pipe less than seventy centimeters in diameter, with oxygen growing scarcer. The twitch at the corner of Lu Chenzhou’s left eye returned, more pronounced this time. He unconsciously clenched his fist, nails digging into his palm, bringing sharp pain. He closed his eyes, took a breath of the thin air saturated with rust and ammonia, and when he opened them again, only cold resolve remained in his gaze. "No alternate route," he stated the fact, his voice regaining its flat tone. "Staying consumes oxygen, increases exposure risk. Continue forward, maintain highest alert. Anvil, prepare the hydraulic cutter. Glasses, monitor for any thermal signals or vibration anomalies." "Yes," came three subdued responses. He turned first, facing the deeper darkness toward which the mucus trail extended, and began crawling again. This time, slower, each movement of elbow and knee doubly cautious, avoiding those reflective, unsettling pale yellow areas. The smell of the mucus clung like a shadow, mingling with the dust of death, forming a nauseating path into the unknown. The pipe began to show a clear upward incline. The rust on the inner walls seemed slightly reduced, but the feeling of being watched, the creeping dread, grew stronger. More than once, Lu Chenzhou felt extremely faint vibrations, not from his teammates, seeming to come from deep within the pipe walls—or perhaps it was just illusion. Finally, a different outline appeared ahead. A standard square ventilation grate, equally rusted but structurally relatively intact, embedded at the pipe’s end. Beyond the grate, a different light faintly seeped through—not natural light, but something steady, dim, akin to emergency lighting or equipment indicator lights. An extremely faint, low hum of machinery could also be heard. Peripheral equipment room outside the sub-archive. The destination had arrived. Lu Chenzhou stopped before the grate, listening and observing carefully for several minutes. No footsteps, no voices beyond the grate, only the regular hum of machinery. He gestured backward. Anvil passed the hydraulic cutter forward again. Lu Chenzhou carefully positioned the cutter jaws on the rusted mounting bolts at the grate’s four corners, applying force one by one. *Crack… snap.* *Crack… snap.* The sound of bolts shearing was piercingly clear in the silence. Each one tightened the heart. With all four bolts cut, Lu Chenzhou held the grate, slowly pulling it inward. A relatively fresh airflow carrying the smell of machine oil and faint ozone drifted in. He greedily inhaled, even though that air wasn’t clean either. He was the first to crawl out of the ventilation shaft, his body landing in a relatively spacious area. Underfoot was a concrete floor covered in dust and oil stains. Before him was a dim equipment room, lined with old distribution cabinets, humming voltage stabilizers, and some metal boxes of unknown purpose. The only light source came from a few dark green emergency lamps in the corner, casting everything in a sickly hue. Glasses, Anvil, and Old Wu crawled out one after another, each landing with the slight stagger and suppressed panting of survivors. The four quickly dispersed, taking cover behind equipment, their eyes sweeping warily across this unfamiliar space. Temporarily safe. Lu Chenzhou leaned back against a cold distribution cabinet, slowly exhaling a breath of stale air he had been holding in his chest. He raised a hand to press his earpiece, switching to the encrypted channel with Qin Wangshu. "Raven has returned to the nest," he said in a low voice, using the predetermined code to signal the successful infiltration. The earpiece was silent at first, only the faint crackle of static. Then, Qin Wangshu's voice came through, also hushed but clear and steady: "Received. There's interference on the nest perimeter. The safe window may be shorter than expected. Your status?" "Unexpected discovery. Inside the pipeline, there is..." Lu Chenzhou's words suddenly cut off. Because another voice, a calm, gentle, male voice with a hint of metallic resonance, abruptly cut into the same encrypted channel, overriding Qin Wangshu's signal. "Mr. Lu," the voice said. It was Gu Zhixing. "It seems Plan B is proceeding quite smoothly. Congratulations on successfully reaching the equipment room." Every muscle in Lu Chenzhou's body tensed instantly, like a bowstring drawn taut. His right hand shot to the pistol at his side, his gaze sharp as a blade sweeping the surrounding darkness. Glasses, Anvil, and Old Wu also froze simultaneously, the blood draining from their faces. How did Gu Zhixing know this channel? How did he know they were here? "Don't be nervous," Gu Zhixing's voice remained steady, even carrying a hint of polite apology, as if interrupting an unimportant meeting. "I merely wish to remind everyone that the equipment room's backup power will automatically switch over in three minutes. At that time, there will be a full-area lighting restart lasting approximately ten seconds. For the sake of your concealment, I suggest finding a visual blind spot in advance." He paused, his tone taking on an elusive, almost sigh-like quality. "Additionally, regarding those... minor inconveniences you saw in the pipeline," Gu Zhixing said slowly, each word striking Lu Chenzhou's eardrum with crystal clarity. "Twenty years ago, during the first large-scale renovation of the Shen residence's underground structure, the emergency backup escape route used by that survey team also went through that ventilation duct." Lu Chenzhou's blood seemed to freeze in an instant. "They reported at the time that the pipeline was 'clean, unobstructed,'" Gu Zhixing's voice was like a cold snake slithering into their ears. "Later, all seven members of that survey team died one after another within three months of the project's completion due to 'accidents.' The archive records it as coincidence." He gave a light laugh, devoid of any warmth. "Of course, we all know there is very little coincidence in this world." He paused, letting silence spread across the channel for two seconds. "I simply feel that history sometimes likes to repeat itself. Those who walk the old path are prone to meeting old friends," Gu Zhixing said, his tone turning businesslike again. "Well then, I wish you all a pleasant exploration of the equipment room. Remember, three minutes." *Click.* The communication was cleanly and decisively severed. The encrypted channel was left with only an absolute, dead silence, a suffocating busy tone. The low hum of machinery in the equipment room now sounded like the breathing of some gigantic, slumbering creature. Lu Chenzhou leaned against the cold metal cabinet, motionless. The sickly green light of the emergency lamps reflected on his face, carving his features hard as stone. Slowly, he raised his hand, looking at the deep, crescent-shaped blood marks his own fingernails had dug into his palm. In his ears, Gu Zhixing's words—"Twenty years ago... also went through that ventilation duct" and "they never made it out"—echoed like a cold curse in this dim space reeking of machine oil and ozone, playing over and over. The fresh, corrosive, bizarre slime in the pipeline... The "accidental" total annihilation of the survey team twenty years ago... Gu Zhixing not only knew about Plan B; he had been waiting for them to walk in. To walk into this death trap, another version laid out across twenty years of time, already prepared. He released his grip on the gun, tapping the cold barrel twice with his fingertips. Then, he turned to the other three, his voice low yet resolute: "Find cover. Wait for the lights to come back on. And then—" He looked toward the darkness, "we go in."