The chill crawled up his spine, like an invisible film swiftly wrapping around his limbs. Lu Chenzhou leaned against the closed door, the *click* of the old-fashioned lock still vibrating in his eardrums. The information left by Qin Wangshu—the anonymous letter, Gu Mingyuan’s name—churned in his thoughts like shards of ice. He needed to sort it out, but more importantly, he needed to verify it. And the first step of verification was on that USB drive. He walked into the study without turning on the lights. The city lights outside faintly outlined the desk. He went to the desk, opened his laptop, and inserted the silver USB drive he’d found in the jacket into the port. The system recognized it, a folder popped up containing a few blurry scanned old documents. He was about to click on them when his phone vibrated twice on the desk simultaneously. Two new messages, from an unknown number. *「Did the buzzing sound nice?」* *「Are you sure what’s on the USB drive is what you’re looking for, or what someone else wants you to find?」* The timestamp was precise to the second, precisely to the moment he had just bent down to pick up the jacket, his right foot stepping down, feeling the hard corner of the USB drive press against his ankle. Right here in this room. Someone was watching. Had been watching all along. He jerked his head up, his gaze sweeping across the silent room, finally landing on the window with its heavy drawn curtains. He grabbed his phone and jacket and swiftly left the apartment. The street at four in the morning was empty and gleaming. Lu Chenzhou stood under the lights at the convenience store entrance, the glow from his phone screen reflecting off his white-knuckled fingers. The glass door slid open and shut, the mechanical "Welcome" repeating three times. The paper cup of hot Americano clenched in his left hand was losing its warmth to his palm. In the wet, reflective ground, he could see the inverted image of the convenience store sign and his own elongated, motionless shadow. The refrigerator behind him emitted a continuous low hum. He took a deep breath and turned back into the convenience store. "Thanks." Lu Chenzhou took it and lit it. The tar-like smell of burning tobacco instantly overpowered the aroma of coffee. He took a deep drag, the smoke circling in his lungs before slowly escaping through his nostrils. He watched the clerk through the haze—the other had already lowered his head again, fingers swiping rapidly across his phone screen as if playing a game. But the rhythm of the swipes was off. Too fast, too regular, like tapping out some kind of code. Lu Chenzhou turned and left. The glass door slid open again. This time, he didn't linger, heading straight for the subway station entrance at the street corner. His pace was neither hurried nor slow, the red glow of the cigarette tip flickering in the dim morning mist. The escalator at the subway station entrance was already shut down. He descended the steps, his footsteps echoing in the empty passageway. At the end of the passage, a cleaner was slowly mopping the floor, the dirty water in the bucket emitting a smell of bleach mixed with grime. As Lu Chenzhou passed, the cleaner looked up and glanced at him. Eye contact lasted less than half a second. But it was enough. Lu Chenzhou recognized that face—three days ago, near the parking lot in the southern part of the city, he had seen this person. At the time, the man was wearing an orange sanitation worker's vest, pushing a garbage cart. As he passed by, the shoelace on his left foot was untied. Today, the shoelace was tied tightly. Lu Chenzhou didn't pause, continuing forward. He descended a second set of stairs and entered the station concourse. The morning subway hadn't started running yet; the concourse was empty, only a few rows of stainless steel seats reflecting the stark white lighting. He walked to the trash can in the corner, stubbed out the half-smoked cigarette, and tossed it in. Then, he pulled an old Nokia feature phone from his jacket's inner pocket—a disposable prepaid SIM card, picked up from a second-hand market just yesterday. He pressed the power button; the screen lit up with a blue glow. His fingers moved quickly over the keypad, inputting a string of numbers. Dial. The ringtone sounded only once before it was answered. "Speak." Qin Wangshu's voice came through the receiver, low-pitched, with the faint sound of traffic in the background. "Convenience store downstairs." Lu Chenzhou said. "Now." "Ten minutes." Qin Wangshu paused. "Are you sure there's no tail?" "There is." Lu Chenzhou said. "At least "Who saw it?" "The informant." "Reliable?" "He used to be." Qin Wangshu said. "Now... I don't know." The corner of Lu Chenzhou's left eye twitched slightly. He raised his hand and pressed the knuckle of his index finger against it. "You're investigating Gu Mingyuan too." "This is my case." "And mine." Lu Chenzhou said. "The timing of the anonymous letter is too coincidental. Gu Mingyuan returns to the country, the anonymous letter appears, Old K's death certificate has issues... all these things clumping together is no coincidence." "So you suspect me?" A trace of tension crept into Qin Wangshu's voice. "Suspect that I deliberately led you to investigate Gu Mingyuan, so you'd run into something?" "I'm verifying." Lu Chenzhou said. "Verifying the intelligence, verifying the risks, verifying... you." A short, sharp exhalation came from the other end of the line, as if suppressing something. "Ten minutes." Qin Wangshu repeated. "Convenience store, ready-to-eat section. I'll wait five minutes, no more." "Understood." "And one more thing, Lu Chenzhou." Her tone suddenly turned icy. "Don't expect me to collect your body. If this is a trap today, if one of the groups watching you is arranged by me—I won't save you. Do you understand?" Lu Chenzhou's fingers holding the phone tightened. The plastic casing emitted a faint creak. "Understood," he said. The call ended. He put away the Nokia and turned toward the exit on the other side of the station hall. His steps remained steady, but the rhythm of his breathing had changed—shallower, faster, as if restraining something. By the time he walked out of the subway station, a layer of grayish-white had begun to spread across the horizon. The morning fog was starting to disperse, the outlines of the streets gradually clearing. The black sedan was still across the street. Lu Chenzhou crossed the road and headed straight for the convenience store. The glass door slid open, the hum of the refrigerators washing over him. He walked to the ready-to-eat section and sat down on a plastic chair by the window. Outside, the window of the black sedan slowly lowered a crack. He glanced at it, then looked away. He took out the packet of Hongtashan from his inner jacket pocket and pulled out another cigarette. The lighter spun once in his fingers, clicking as he lit it. Smoke rose, blurring the reflection in the glass window. Five minutes. He stared at the digital clock on the convenience store wall. The second hand jumped tick by tick, its sound swallowed by the hum of the refrigerators. Condensation droplets slid down the glass door of the cooler, leaving a winding wet trail. The air held the burnt bitterness of coffee, the salty savoriness of oden, and the faint smell of tobacco clinging to him. And... the smell of disinfectant. Very faint, mixed in with the food smells, almost imperceptible. But Lu Chenzhou smelled it. He looked up. Qin Wangshu walked out from behind the shelves, holding a bottle of mineral water. She wore a dark gray jacket and jeans, her hair tied in a low ponytail, her expression neutral. She walked to the ready-to-eat section and sat in the chair opposite Lu Chenzhou, unscrewed the cap, and took a sip. Between them was a greasy plastic table. "Car's parked two streets over." Qin Wangshu spoke first, her eyes on the window. "Took three minutes to walk here. Didn't see any tails on the way, but not sure if any cameras caught me." "There's a car across the street." Lu Chenzhou said. "Black Volkswagen, license plate ending in 37. Been there at least twenty minutes." "Shen Yan's people." Qin Wangshu said. "I recognize that car. Followed me once last month." "What about the other group?" "Don't know." She set the water bottle down, her fingers unconsciously rubbing the bottle. "More professional, more concealed. That cleaner at the subway entrance—I took a look before coming in, he's already gone. The bucket is still there." Lu Chenzhou's fingertip tapped lightly on the tabletop. Very lightly, almost inaudible. "What was Gu Mingyuan doing at the West Suburb factory area?" he asked. "Exchanging something." Qin Wangshu said. "The informant saw him go in empty-handed, come out carrying a briefcase. The bag was heavy; judging by how he carried it, it wasn't just documents inside." "Who was he exchanging with?" "Didn't see." Qin Wangshu paused. "The informant said there was another person in the workshop at the time. Back to the door, wearing "Unless," Qin Wangshu repeated, her voice tinged with weariness. "But I've checked. The forensic examiner who handled Old K's case back then, the funeral home staff, the cemetery administrator... Everyone's testimony matches up. No flaws." "No flaws are the biggest flaw," Lu Chenzhou said. "Too perfect. Perfect as if rehearsed." Qin Wangshu didn't respond. She screwed the cap back on the water bottle and placed it on the table. The plastic bottom made a dull thud against the tabletop. "You plan to go to the western suburbs?" she asked. "There are photos in the encrypted message." Lu Chenzhou took out his smartphone—not the Nokia, the one he used daily—unlocked it, and pulled up the message from the unknown number. The photo was blurry, as if taken hastily from a moving car. The street scene was receding quickly, but in the corner, a side profile wearing a beige trench coat was frozen in the frame. In the background, on a rusted metal sign, the characters "Xi Jiao Fang Zhi" (Western Suburbs Textile) were faintly visible. Qin Wangshu took the phone and zoomed in on the photo. Her fingertips slid across the screen, slowly, carefully. "The photo was sent half an hour ago," Lu Chenzhou said. "The send time was exactly when I was checking the message outside the convenience store." "Someone is monitoring your location in real time," Qin Wangshu put down the phone and pushed it back to him. "Then sending you hints—or bait." "I know." "And you still want to go?" "I'm going," Lu Chenzhou said. "If it's bait, it means they want me to see something. If it's a hint..." He paused. "It means someone wants to help me but doesn't dare show themselves." "Help you?" Qin Wangshu laughed, a cold laugh. "Lu Chenzhou, no one in this world will help you. Not ten years ago, and certainly not now. Everyone is using you. Including me." The air froze for a few seconds. The hum from the freezer suddenly changed pitch, as if the compressor had kicked in, the buzzing abruptly intensifying. Water droplets on the glass door of the refrigerated cabinet slid down faster, plopping into the metal tray below with a soft splash. "Including you?" Lu Chenzhou repeated. Qin Wangshu met his gaze. Her pupils looked very dark, very deep under the convenience store's stark white light, like two wells. "Yes," she said. "I asked you to investigate Gu Mingyuan because I wanted to know if he was connected to Shen Yan's death. I told you about the western suburbs factory area because I wanted to use your eyes to see what I couldn't. I'm sitting here talking to you because I need to get information from you, to judge whether that USB drive in your hand is worth the risk for me." She spoke slowly, each word like a stone, dropping one by one onto the table. "So don't expect me to collect your body," she said finally. "If you die in that factory area today, I'll write a report saying you acted without authorization, left surveillance, and died accidentally. I'll transport your body back, perform an autopsy, file it away, and then continue investigating my case. Do you understand?" Lu Chenzhou looked at her. For a long time. Then, he nodded. "I understand," he said. Qin Wangshu stood up. The chair legs scraped against the floor with a sharp sound. She picked up the half-finished water bottle, turned to leave. "Qin Wangshu," Lu Chenzhou called out to her. She stopped but didn't turn around. "Old K's death certificate back then," Lu Chenzhou said. "When you accessed the file, did you notice the handwriting of the signature?" Qin Wangshu's back stiffened slightly. "What about the handwriting?" "Too neat," Lu Chenzhou said. "Neat as printed type. Old K was left-handed, his handwriting slanted to the right. But the signature on that death certificate was straight, upright, with uniform ink depth—it didn't look handwritten. It looked stamped." Qin Wangshu slowly turned around. Her face looked somewhat pale under the light. "When did you discover this?" "Last night," Lu Chenzhou said. "I couldn't sleep, so I went through all the scanned documents from the old case again. On the thirty-seventh time through, I noticed." "Why didn't you say something earlier?" "I was waiting," Lu Chenzhou said. "Waiting for you to tell me yourself." They stared at each other. The air in the instant food area seemed to have stopped flowing, only the freezer's hum continuing, like a never-ending electrocardiogram in the background. Qin Wangshu's lips moved slightly, The photo was much clearer than the previous one. The shot was taken from a high angle, looking down, as if from the roof or a window of a building. In the center of the frame, the door of Workshop No. 3 in the old western suburbs textile factory district was wide open. A silver sedan was parked at the entrance, its door open. A man in a beige trench coat was bending down, getting out of the car—it was Gu Mingyuan. And deep inside the workshop, standing in the shadows, was another person. A grey hoodie, the hood pulled low. The left hand hung at their side. On the web between the thumb and forefinger, a white scar stood out starkly in the dim light. The photo's timestamp read: three minutes ago. Lu Chenzhou stared at that scar. He stared for a long time. Then, he turned off the screen, stuffed the phone back into his pocket, and stood up. The chair legs scraped a short, sharp sound against the floor. He walked to the checkout counter and returned the disposable lighter to the clerk. "Thanks," he said. The clerk looked up, glanced at him, took the lighter, and tossed it back under the counter. The scar on the little finger of his right hand flashed once under the light. Lu Chenzhou turned and left the convenience store. As the glass door slid open, he took one last look across the street. The windows of the black Volkswagen were rolled up now. But the car hadn't moved. He stepped into the morning mist, quickening his pace. He wasn't heading home, nor towards the subway station. He turned into a narrow back alley. The ground was slick, overgrown with moss. On either side were the blank back walls of old residential buildings, windows shut tight, curtains drawn. When he reached the middle of the alley, he stopped. He pulled a coin from his jacket's inner pocket, crouched down, pretending to tie his shoelace. The coin slipped from his fingers, clinking as it rolled deeper into the alley. Maintaining the shoelace-tying posture, head bowed, he used his peripheral vision to scan the alley entrance. No one had followed him in. But he knew this was only temporary. The person in the car across the street would move sooner or later. The cleaner who vanished at the subway entrance might be waiting around some corner. And deeper still, the person who sent the encrypted message—whether friend or foe—was undoubtedly watching him from somewhere right now. Lu Chenzhou finished tying his shoelace and stood up. He didn't bother retrieving the coin, just continued walking forward. The end of the alley opened onto a wider road where morning shift buses had already started running. He walked to the bus stop and blended in among a few elderly people waiting. A bus arrived. He was the last to board, dropped his fare, and walked to the very back, taking a window seat. As the bus started moving, he took out the smartphone and opened the photo again. Zoomed in. Zoomed in further. The figure in the grey hoodie became blurry within the pixels, but the scar on the web of the hand remained clear. Like a mark carved into memory. Like the wound on the web of Old K's left hand, still oozing blood that rainy night ten years ago, when he handed Lu Chenzhou that forged confession. Lu Chenzhou closed his eyes. The bus rattled towards the western suburbs of the city. The scenery outside the window began to grow desolate. Tall buildings and skyscrapers gradually gave way to low-rise factories and warehouses. The smell of dust in the air grew heavier, mixed with a faint, drifting scent of textile dye from somewhere in the distance. He knew he was walking into a trap. Or towards the truth. Or both. His phone vibrated once in his pocket. He took it out and unlocked it. A third message. This time, only one line: **「Workshop No. 3, ventilation duct in the northeast corner. Left something for you.」** Sent: Ten seconds ago. Sender: Unknown. Lu Chenzhou stared at the line, his finger hovering over the screen. The bus announcement sounded: "West Suburbs Textile Factory District. Passengers getting off, please prepare." He stood up and walked towards the rear door. The door opened. The cold morning air rushed in, carrying the smell of rust and engine oil. He jumped off the bus, his feet landing on the pitted concrete ground. The bus stop was soon left behind, the vehicle's exhaust trailing a greyish-white streak through the morning mist. Ahead, the rusted iron gate of the old West Suburbs Textile Factory District swayed gently in the wind, emitting a rhythmic creak—clang. Like a door to the past. Slowly swinging open. The light from the phone screen reflected on Lu Chenzhou's face, The automatic door slid open again, the mechanical "Welcome" sounding like some kind of mockery. The clerk was dozing behind the cash register, the fluorescent light above buzzing. Lu Chenzhou walked to the innermost shelf, picked up a pack of the cheapest tissues, paid, got his change. Throughout the entire process, his gaze kept sweeping across the glass door outside—the newsstand across the street was closed, under the streetlight there was no one, a black car was parked in the shadow of trees in the distance, its windows tinted dark. Nothing unusual. That was what was most unusual. Lu Chenzhou walked out of the convenience store, not heading directly home. He turned into the alley next to it. The alley was narrow, flanked by the rear walls of old residential buildings, the base of the walls piled with broken furniture and moldy cardboard boxes. He walked quickly, his footsteps rebounding between the walls, forming overlapping echoes. Halfway through, he suddenly stopped, pressed himself sideways against the wall, and held his breath. Five seconds. Ten seconds. An extremely faint footstep came from the alley entrance—not leather shoes, but soft-soled sneakers, almost silent on the damp cement ground. But Lu Chenzhou heard it. He heard the footsteps pause at the alley entrance, hesitate, then continue forward, rhythm steady, neither hurried nor slow. Not a passerby. Lu Chenzhou took the Nokia feature phone from his pocket, turned it on, pressed a shortcut key. An encrypted messaging interface preset by Fang Mu popped up on the screen. He quickly typed: "Tail confirmed, at least one. Shen Yan's people?" Send. He continued walking forward, didn't look back. The end of the alley was a T-junction, left leading to the main road, right to an even narrower lane. Lu Chenzhou chose the right. The lane's ground was paved with bluestone slabs, moss growing slippery in the gaps, the air carrying a faint musty smell and the oily scent drifting from a distant breakfast stall. He quickened his pace, almost breaking into a jog, then at the third fork, abruptly turned left, ducking into the entrance of a residential building's unit. The stairwell was dark, the motion-sensor light broken. Lu Chenzhou leaned against the back of the door, peering out through the crack. Thirty seconds later, a man in a gray jacket appeared at the mouth of the lane. Medium build, wearing a baseball cap, the brim pulled low. The man stopped at the fork, looked left and right, then took out his phone and glanced at it. The screen's light illuminated the lower half of his face—a mole at the corner of his mouth. Lu Chenzhou memorized that mole. The man headed in the direction of the main road, his pace noticeably quickening. Lu Chenzhou didn't immediately follow out. He waited in the dark for another five minutes, until the engine sound of an early bus came from the distance, then pushed open the unit door and walked in the opposite direction—towards the western suburbs. *** The subway passage was damp and stuffy. The morning rush hadn't started yet. A few early-rising workers heading to their jobs stood scattered on the platform, carrying tool bags, their eyes vacant. Lu Chenzhou blended into the crowd, swiped his phone to enter the station, and boarded the train heading for the western suburbs. The carriage was empty. He chose the seat farthest inside and sat down, his back to the direction of travel. The train started. The ad lightboxes outside the window blurred into a continuous band of light. Lu Chenzhou's left eyelid began to twitch, faintly, uncontrollably. He clenched his phone, his knuckles turning white. The steam had long since vanished from his coffee cup, and a drop of condensation from the rim fell, striking the concrete floor, leaving behind a dark, circular mark. He zoomed in on the photo, then zoomed in again. The profile of the trench coat man... resembled Gu Mingyuan. But he wasn't sure. The light was too dim, the resolution too low. Lu Chenzhou closed the photo, opened a map app, and searched "western suburbs textile factory." Three results popped up: two had already been converted into creative parks, only one—Hongqi Textile Factory No. 3—was marked as "abandoned." Its location was on the edge of the western suburbs, near the freight railway, surrounded by large tracts of undeveloped wasteland. This was the place. The train arrived at the station. Lu Chenzhou got off with the scattered passengers. The exit was deserted, only a vendor pushing a breakfast cart, steam rising from the bamboo steamers. He bought two steamed buns, paid in cash And as for me," he paused, his gaze finally lifting to meet Lu Chenzhou's eyes, "I have to leave before the third party arrives." Third party. Lu Chenzhou's heart clenched violently. His left hand gripped the edge of the ventilation duct, causing flakes of rust to fall with a soft rustle. His right hand still held the small metal box, his knuckles white from the force. He understood in an instant—the man in the tracksuit tying his shoes in the subway was Shen Yan's eyes. But there had been another gaze back then, farther away, colder, like observing a specimen through glass. Not the police's style. Now, that third party was also biting at their heels. "The thing Gu Mingyuan gave you," Old K continued, his pace deliberate but each word hitting like a nail, "is not evidence. It's bait. Shen Yan used it to hook you, then uses you to hook me. Very old-fashioned, but effective." He nudged the photos at his feet with his boot. "Take a look. Decide whether to believe it after you see them." Lu Chenzhou let go, landing on the floor. The movement was light, but a dull pain shot through his knee—banged when he'd squeezed through machinery gaps in the textile mill workshop earlier. He crouched down and picked up a photo. A black-and-white image, blurry. The angle was that of a covert shot. Two people stood by a pier. One, hunched over, was Gu Mingyuan. The other, shown in profile, wore a baseball cap; the scar on the back of his left hand was clearly visible. A timestamp in the bottom right corner: August 23, 2014. Four years after Old K's "death." Lu Chenzhou flipped through them one by one. 2015, a meeting in a teahouse. 2016, entering an office building one after the other. 2017... 2018... The most recent one, from three months ago, showed Gu Mingyuan handing the small metal box to the other person—exactly the scene that had unfolded in the textile mill workshop early this morning. On the edge of each photo, extremely fine handwriting noted latitude, longitude, and time, precise to the second. This was the mark of professional surveillance, not amateur tailing. "Monitoring Gu Mingyuan for ten years," Old K's voice came from the direction of the workbench, carrying the echo of tapping on a metal keyboard, "wasn't to protect him. It was to wait for him to contact 'me' again." He tapped the keyboard; the data stream on the screen paused, freezing on a line of encrypted addresses. "He made contact today. In your police parlance, this is called 'closing the net.'" Lu Chenzhou looked up, his gaze sweeping over the row of dust-covered transom windows high up in the workshop. Outside, the sky was a pale gray. In the distance, the rusted iron gate of the textile factory swayed in the wind, the rhythmic *creak—clang* faintly audible. The sound now felt like a countdown. "Then why did you show yourself?" "Because Shen Yan's net is cast wider than you imagine." Old K shut down the computer, unplugged the USB drive, his movements crisp. He stuffed it into an inner pocket of his jacket, zipping it all the way up. "Gu Mingyuan is just the bait on the surface. Beneath it, Shen Yan is investigating the circulation records of the wax seal from seventeen years ago—not the fragment you found, but the complete original. He knows the seal passed through three people back then: your father, Gu Mingyuan, and..." He stopped. Lu Chenzhou stood up, the edge of the photo cutting into his fingertip. "Who else?" Old K didn't answer. He walked to the wall, pressed a hidden switch, and a secret door disguised as an electrical panel slid open silently, revealing a narrow passage behind it. A cold wind rushed out, carrying the damp, decaying smell unique to underground drainage systems, instantly diluting the machine oil odor in the workshop. "Seven minutes left." Old K glanced at the old-fashioned digital watch on his wrist, its screen glowing green. "This passage leads to the main sewer line. Walk three hundred meters east, and there's a maintenance shaft. Go up, and you'll be on the back street of the old goods market. Fang Mu's car should already be waiting nearby—if he's smart enough." Lu Chenzhou didn't move. His hand holding the photo hung at his side, the other still gripping the small metal box. Its coldness seeped through his skin into his bones. "You haven't answered my question." Old K already had one foot inside the passage. He looked back, shadows covering most of his face, only his eyes shining sharply in the dim light. "The third person... you know him." His voice dropped even lower, almost scattered by the wind. "And he's outside right now. At least two cars, three directions. The Shen family is blocking the southern intersection; another group holds the high ground to the north. The traces you left when you came in are enough for them to lock down this entire block." He paused. The last sentence sliced through the air like a blade. "Officer Lu, you're not the hunter now. You're the prey trapped in the middle. Choose—follow me through the secret passage, or stay here and wait for them to come in and ask you about the wax seal. How do you think they'll ask?" The wind from behind the secret door continued to blow, making the photos on the floor flutter slightly. Those frozen faces stared at the ceiling from the grease stains. Lu Chenzhou heard the faint, low hum of idling car engines in the distance. More than one. Pressure closed in like icy tidal water from all sides. He tightened his grip on the metal box, his fingertips touching those fine scratches—Gu Mingyuan's fingers had repeatedly rubbed the same spot during the handover. What was hidden beneath it? He inhaled a breath of damp, foul air, stepped forward, and walked toward the secret door. "The third handler," Old K turned slightly, half his face buried in the shadows of the passage, "codename 'Gray Pigeon'. Seventeen years ago, he was the night shift administrator of the archives. The night before the case was closed, when the wax seal was stolen, it was he who signed the loss report." He paused, his voice dropping even lower. "Three days ago, 'Gray Pigeon's' body was found at the West Suburb Reservoir. Cause of death was drowning, but there were no diatoms in his lungs—meaning he was thrown into the water after he died." A chill crawled up Lu Chenzhou's spine. "Shen Yan is silencing people." Old K took one last look toward the workshop. "Cleaning up all those who know about the seal. Gu Mingyuan is next. And you," his gaze fell on the metal box in Lu Chenzhou's hand, "you're holding the bait. You're a moving target." A muffled impact sounded from afar—the sound of an iron door being rammed. Shen Yan's people were starting to try to break in. "Coming or not?" Old K had already stepped into the passage. Lu Chenzhou took one last look at the photos scattered on the floor, picked them all up, and stuffed them into his jacket's inner pocket. The metal box pressed against his chest, the outline of the button digging into his ribs. He followed Old K and ducked into the secret door. The passage was very narrow, only wide enough for one person. The walls were rough concrete, covered with moldy water stains. Every few meters overhead was an emergency light, its dim glow barely illuminating the path underfoot. Old K walked quickly, his footsteps as light as a cat's. Lu Chenzhou had to push himself to keep up. "How did Fang Mu cooperate with you?" Lu Chenzhou asked, keeping his voice low. The passage had an echo; volume had to be controlled. "He didn't cooperate with me." Old K didn't look back. "He cooperated with the emergency protocol you set up. Once contact is lost beyond the preset time limit, the backup communication channel activates automatically. I just... placed an encrypted message in that channel ahead of time." "How do you know the details of my protocol?" This time, Old K stopped. He turned around. The light from the emergency lamp hit him from the side, making the wrinkles on his face look like knife-carved trenches. "Because ten years ago, ten years ago." Old K corrected him. "The one who survived is a man who needs to hide." He continued walking forward. "Now, we need to hide even deeper. Because Shen Yan is not the only hunter." A fork appeared ahead in the passage. Old K unhesitatingly chose the darker left path. The smell of rot in the air grew heavier, and the faint sound of flowing water could be heard. "The third party," Lu Chenzhou caught up, "who is it?" "Don't know." Old K answered bluntly. "But the man in black tracksuit who followed you this morning isn't Shen Yan's man. His movement patterns are more... militarized. And," he stopped again, pulling a palm-sized electronic device from his pocket, the screen showing jumping signal waveforms, "he left a tracker on you. Non-civilian frequency, high encryption level. I blocked the signal, but it's only a temporary jamming. Once we leave the jamming range, he'll know your location immediately." Lu Chenzhou instinctively patted all his pockets. Phone, keys, ID... Finally, in the inner lining of his inner pocket, he felt a button-sized hard object. Very thin, metal shell, faint magnetic pull on the back. He pried it out, pinching it between his fingertips. "When..." He remembered the passerby who bumped into him at the convenience store entrance early that morning. The action was light, the apology quick; at the time, he'd thought it was just an accident. "At least two hours ago." Old K glanced at the electronic device. "Stable signal source, means the battery can last at least twenty-four hours. Professional-grade stuff." He took the tracker, crushed it forcefully, the tiny circuit board inside making a faint cracking sound. "But destroying it, the other side will immediately notice something's wrong. We need to speed up." The sound of flowing water grew louder. At the end of the passage appeared an iron grate; beyond the grate was a wide main sewer channel, turbid water rushing past, garbage and foam floating on the surface. A rusted padlock hung on the grate. Old K pulled a special key from his waist, inserted it, twisted. The lock opened. "Walk along the channel edge, three hundred meters, there's an iron ladder going up." Old K pushed open the grate, damp water vapor hitting his face. "After going up, turn left, cross the old goods market, Fang Mu's car is parked at the back door of 'Old Wang Hardware Store.' License plate ending 347." Lu Chenzhou stepped out of the grate, his feet on the slippery concrete channel edge. He looked back; Old K was still standing inside the passage, not seeming to follow. "You're not coming?" "I have my own path." Old K said. "Remember, the button in the metal box, it's not YKK's 'Y'. It's the Greek letter 'Υ' — in physics, it represents the 'wave function.' Gu Mingyuan wanted to tell you not a zipper brand, but a location: the old site of the Wave Function Research Institute, northern suburbs, abandoned for years." He paused, giving Lu Chenzhou one last look. "And, be careful of Fang Mu." The grate closed again in front of Lu Chenzhou. The padlock fell back into place with a soft *click*, almost inaudible against the sound of rushing water. Old K's figure disappeared into the depths of the dim passage. Lu Chenzhou stood still, holding the now-empty metal box in his hand. The roar of the channel water filled his ears, the damp, rotten air seeped into his nostrils. He glanced at the watch on his wrist — Jamming failure, one minute left. He turned and sprinted along the channel edge. "Of course, you can also call me 'Gray Pigeon.'" The worker added, the corner of his mouth twitching again. "That's what Gu Mingyuan called me during the handover today. Though I think the name is pretty stupid — a pigeon? Can't fly very high, doesn't live many years." Lu Chenzhou's fingers tightened. The edge of the metal box dug into his palm, the pain sharp and clear. He needed this pain to suppress the fragments surging in his mind: the wound on the back of Old K's left hand when he handed over the forged confession that rainy night ten years ago; the seemingly intentional, unintentional backward glance when "Gray Pigeon" left the abandoned textile factory; and now, the rhythmic stamping sounds in this underground workshop, the scent of rosin and solder permeating the air. "Come down." The worker said for the third time. This time, he pulled over a folding chair and placed it opposite the workbench. "We don't have much time. Shen Yan's men are stupid, but they brought signal trackers. The interference pulse from that smartphone you Lu Chenzhou pushed open the fence and jumped down. His knees bent slightly upon landing, cushioning the impact. Dust billowed up from his feet, swirling in the flickering fluorescent light. He straightened up, his eyes quickly sweeping the entire space: about fifty square meters, cement floor marked by repeated washings; at least thirty finished metal boxes of uniform specifications were stacked on shelves against the wall; the stamping press had cooled down, a semi-finished copper sheet still stuck in the mold; on the workbench, besides a laptop, sat an old oscilloscope, its waveform pulsing steadily. And besides the scents of rosin and solder, there was a faint, extremely subtle… smell of blood. Very faint, mixed with the odors of machine oil and dust, almost imperceptible. But Lu Chenzhou smelled it. His gaze fell on the back of the worker’s right hand—a band-aid was stuck there, with dark red seepage around the edges. "Sit," the worker pointed at the folding chair. Lu Chenzhou didn’t sit. He stood on the other side of the workbench, maintaining a distance of two meters. From this angle, he could see part of the content on the laptop screen: among the encrypted log entries, a codename "Nightingale" appeared repeatedly, along with a set of six-digit date codes, the most recent being "231015"—ten days ago. "What was in the box Gu Mingyuan gave you?" Lu Chenzhou asked, his voice steady again. "You might as well ask first," the worker pulled out a crumpled pack of cigarettes from the workbench drawer, took one out and lit it, smoke coiling in the harsh light, "who Gu Mingyuan works for." "Shen Yan," Lu Chenzhou said. "Shen Moqing?" The worker laughed, the sound dry and raspy. "If Shen Moqing could control Gu Mingyuan, the Gu family wouldn’t have lost so badly in that board meeting three years ago that they had to mortgage their ancestral home." He took a drag, smoke slowly drifting from his nostrils. "Gu Mingyuan is ‘Nightingale’s’ man," the worker said, his gaze fixed on Lu Chenzhou’s face, as if observing his reaction. "Or rather, a piece that ‘Nightingale’ can still move right now. As for who ‘Nightingale’ is… the box in your pocket, open it and you’ll know." Lu Chenzhou didn’t reach for the box. "Why are you helping me?" he asked. "Helping you?" The worker raised an eyebrow. "When did I help you? I let you hide in here because you were being chased by two groups, making too much noise, which would expose my hideout. As for telling you this…" he flicked ash from his cigarette, "it’s just a transaction." "What transaction?" "The box in your hand," the worker said. "Open it, read what’s inside. Then, tell me the contents." "Why don’t you open it yourself?" "Because the box’s encryption lock is biometric." The worker lifted his right hand, waving the band-aid. "It requires a specific DNA sequence to activate. Mine won’t work. Gu Mingyuan’s won’t either. But yours…" he paused, "Ten years ago, that confession letter you signed, the pen you used, the refill had a hidden blood collection needle. Remember?" Lu Chenzhou’s breath stopped. Memory pierced through time like an ice pick—the stark white light of the interrogation room, the black fountain pen handed to him, the barrel cold to the touch as he grasped it and signed his name at the bottom of the page. A slight sting in his fingertip, which he had dismissed as a trick of his nerves. "They took a blood sample from you," the worker’s voice drifted through the smoke. "Not a full sample, just epidermal interstitial fluid and trace blood cells. Enough to extract DNA and make it the key for the encryption lock. This box can only be opened by you." Lu Chenzhou clenched his fist. His fingernails dug into the same spot on his palm again, the wound reopening, beads of blood welling up. He could feel the warm liquid trickling along his palm lines, then being absorbed by the