The metal profile groaned and sank abruptly, the sound of bending metal scraping into their eardrums. "Go!" Lu Chenzhou's voice was like a blade scraping metal. Zhou Zhengping closed his eyes, threw his whole body onto it, and began inching forward. His weight caused the two makeshift "bridges" to sway violently, their metal edges scraping against the cement of the opposite rooftop, sending down a cascade of dust and grit. Lu Chenzhou's left hand gripped the security grating, his right hand supporting Zhou Zhengping's waist, his palm feeling the spasms in the old man's muscles and the cold sweat seeping through his clothes. From the direction of the balcony door came the sound of urgent footsteps—someone had rushed into the living room. "The back window! They went out the back window!" From the corner of his eye, Lu Chenzhou saw swaying shadows reflected in the glass. He shoved Zhou Zhengping forward. The old man let out a short cry of surprise, losing his balance, his hands flailing in the air, yet miraculously catching hold of a protruding section of drainpipe on the opposite rooftop. "Grab it!" Zhou Zhengping's fingers dug into the crack at the edge of the drainpipe, his entire body dangling in mid-air, his legs kicking uselessly. Freed of most of the weight, the metal profile sprang upward then dropped back down, striking the security grating with a hollow, echoing clang. Lu Chenzhou didn't hesitate. Bracing one hand on the edge of the security grating, his body coiled like a drawn bowstring and suddenly released, he slipped through the gaps in the mesh. Wind rushed into his collar; from the sixth-floor height, the ground shrank into blurred patches of color. The tip of his foot landed precisely on the parallel profiles, he pushed off, his body lunging forward, his right hand grabbing the edge of the parapet on the opposite rooftop. The rough grit of the bricks and mortar dug into his palm. The muscles in his arm bulged as he hauled himself up. Almost simultaneously, a tremendous shattering of glass erupted behind him. Someone had smashed the balcony door. Lu Chenzhou rolled onto the cement rooftop and immediately turned back to pull up Zhou Zhengping, still dangling from the drainpipe. The old man's face was a purplish-red, his arms trembling like withered branches in the wind. "Give me your hand!" He seized Zhou Zhengping's wrist. The old man's fingers released the drainpipe. Lu Chenzhou pulled with a sudden burst of strength, dragging the man's heavy body up. They both collapsed onto the rooftop, their ragged gasps mingling. The night wind, carrying the distant clamor of the city and the smell of nearby dust, filled their lungs. On the opposite balcony, two dark silhouettes appeared behind the shattered glass door. The beams of flashlights swept across the rooftop, passing over the rusty solar water heater frames and piles of junk. "Go." Lu Chenzhou pulled Zhou Zhengping up and, crouching low, dashed toward the iron door on the rooftop leading to the stairwell. The iron door was rusted shut, secured by an old padlock. Lu Chenzhou fished a piece of thin wire from his pocket—a small tool he habitually carried—and inserted it into the keyhole. His fingers felt the subtle resistance of the internal tumblers. His movements were quick and steady, his breathing held low. Zhou Zhengping leaned against the water tank behind him, his chest heaving violently, his eyes fixed on the opposite rooftop. The figures there were looking for a way across. *Click.* The lock opened. Lu Chenzhou pushed the door open. The smell of aged dust and mildew assaulted them. The stairwell was pitch black, lit only by the sickly green glow of an emergency exit sign somewhere below. He pulled Zhou Zhengping inside, then turned and gently pulled the door shut behind them, not latching it completely. "Down." His voice was close to Zhou Zhengping's ear. "No lights. No sound." Zhou Zhengping nodded, a hoarse, wheezing sound escaping his throat. His steps were unsteady, he nearly missed his footing several times. Lu Chenzhou supported him under one arm, half-dragging, half-carrying him downward. Darkness swallowed them. The rough texture of the cement steps underfoot and the sound of their own suppressed breathing were the only reality. Lu Chenzhou's ears strained to catch the sounds from the rooftop above—muffled voices, the clang of metal, then a stifled curse. The pursuers didn't immediately follow. Perhaps they were assessing whether the two trembling metal profiles could bear the weight of a grown man, perhaps they were calling for backup to block the exits below. When they reached the fifth floor, Lu Chenzhou stopped. He released Zhou Zhengping, motioning for him The fire escape staircase was narrower and steeper. The walls were painted with long-faded, peeling green paint. They descended two floors, and Lu Chenzhou suddenly stopped, raising his hand in a signal. Faint footsteps came from below. More than one person, with a steady rhythm, moving upward. Lu Chenzhou immediately turned, pushed open the fire door on that floor, and returned to the residential building's corridor. The layout of this floor was the same as above, but the air held a faint lingering smell of cooked food. He quickly scanned the area, his gaze locking onto a partially ajar door at the end of the corridor that led to a public balcony. The balcony wasn't large, piled with discarded flowerpots and old furniture from several households. The edge was a waist-high concrete guardrail. Lu Chenzhou walked to the guardrail and looked down. Below was the residential complex's internal green space, sparsely planted with shrubs, and beyond that was the back of another row of buildings. The height was about four stories. Directly below was a patch of half-withered grass. He turned back to look at Zhou Zhengping. The old man's face appeared ghastly pale under the distant streetlight's residual glow, his eyes filled with the words "you're insane." "Jump, or be caught by them," Lu Chenzhou's voice was calmly cruel. "Your daughter is still in their hands. If you're caught, she loses her value immediately." Zhou Zhengping's body trembled violently. He walked to the guardrail, looked at the height below, his Adam's apple bobbing up and down. From the fire escape below, footsteps grew closer. Muffled conversation faintly drifted up: "...check every floor... people at both the front and back doors..." No time left. Lu Chenzhou stopped looking at him. He placed both hands on the guardrail, vaulted over, and dropped. He adjusted his posture mid-air, bending his knees, rolling forward upon landing. The scent of grass blades and soil rushed into his nostrils, a dull impact transmitted through his shoulders and back, but his bones were fine. He quickly got up, looking upward. Lu Chenzhou spread his arms, making a catching gesture. He didn't speak, just stared at him intently with his eyes. The fire door upstairs was pushed open. Light leaked out. Zhou Zhengping closed his eyes, climbed over the guardrail, and dropped straight down. Lu Chenzhou took a step forward. He didn't try to catch him directly. Instead, at the moment Zhou Zhengping was about to hit the ground, he turned sideways and collided with him, altering his falling trajectory while simultaneously grabbing his collar. The two tumbled together onto the withered grass. Zhou Zhengping let out a muffled grunt. Lu Chenzhou felt his own ribs ache from the impact. He immediately scrambled up, pulling Zhou Zhengping to his feet. "Can you walk?" Zhou Zhengping clutched his chest, his face pained, but he nodded. Lu Chenzhou supported him, quickly moving through the green space and ducking into the narrow gap between two buildings. It was filled with construction debris and abandoned bicycles, reeking of urine and rust. They stumbled forward, one step deep, one step shallow. Behind them, from the building they'd left, came faint commotion and the sweeping beams of flashlights. The end of the gap was the residential complex's edge: an iron fence. Beyond it was a dimly lit back alley. The fence wasn't high, topped with anti-climbing spikes, but it was old and poorly maintained, with several spots where the spikes were bent or deformed. Lu Chenzhou found a spot where the spikes were crooked. He first helped Zhou Zhengping climb over, then easily vaulted over himself. When his feet landed on the rough asphalt of the alley, Zhou Zhengping nearly collapsed. Lu Chenzhou forcefully propped him up, dragging him to move close to the base of the wall. The alley was very narrow. Opposite was the back wall of an old residential area, covered in withered vines. A few broken streetlights cast murky halos of light, illuminating piled garbage bags and flowing sewage. "Where... where to?" Zhou Zhengping's voice was hoarse and broken. "Away from their line of sight," Lu Chenzhou answered curtly, his sharp gaze scanning both ends of the alley. No suspicious figures, no parked vehicles. But he didn't dare relax. The other side had managed to precisely surround Zhou Zhengping's home; they must have personnel deployed nearby. They walked along the alley for several dozen meters, then turned into an even narrower passageway cluttered with miscellaneous items. Lu Chenzhou's memory began to function. Based on the map of the old residential area he had studied before coming, he navigated through the maze-like lanes and alleys, "Because you performed the appraisal back then." Lu Chenzhou turned his head, looking at Zhou Zhengping's face blurred in the shadows. "That handwriting appraisal concerning the reimbursement documents of Sun Henian's secretary. You altered the conclusion, didn't you?" Zhou Zhengping's body stiffened. He opened his mouth but made no sound. "Shen Qinghuan and Gu Zhixing pressured you. Maybe others too." Lu Chenzhou continued, his tone steady, as if stating a fact unrelated to himself. "You altered the conclusion, making that forged document appear 'credible.' It was a crucial link in the entire chain. Without that appraisal, many things that followed wouldn't hold up." "I... I didn't..." Zhou Zhengping offered a futile defense, his voice feeble. "Whether you did or not isn't important now." Lu Chenzhou cut him off. "What's important is, they think you know too much. Ten years ago, you were still useful. They let you 'retire' and keep your mouth shut. Now, ten years later, I've found you. To them, this means risk. The simplest way to control risk is to make it disappear. Kidnapping your daughter was to make you obedient, to keep me in the house, to catch us both in one net. A classic cleanup method." Zhou Zhengping slid down the wall, sitting on the ground, burying his head in his hands. "Xiaowen... my Xiaowen... she knows nothing..." "She is now your only bargaining chip." Lu Chenzhou crouched down, meeting his eyes. "If you stay alive and cooperate with me, she has a chance of being exchanged. If you die, or if I'm caught by them, she immediately loses value. Do you understand?" Zhou Zhengping raised his head. His cloudy eyes were filled with tears, but beneath the fear, something seemed to be coalescing. "You... can you save her?" "I can't guarantee it." Lu Chenzhou's reply remained direct. "But I can guarantee that if you don't cooperate, she certainly won't be saved. Cooperate with me, and we at least have a chance to figure out who kidnapped her and what they really want, instead of just being silenced." "What do you want me to do?" Zhou Zhengping's voice still trembled, but there was a hint of resigned determination. "First, leave here, find a safe place." Lu Chenzhou stood up, pulling him to his feet again. "Then, I want you, as an expert, to re-appraise that document from back then, as well as another crucial handwriting sample I have. I need conclusive evidence that can overturn the old conclusion." Zhou Zhengping fell silent. His gaze drifted past Lu Chenzhou, into the depths of the dark alley, as if looking at some distant and painful past. The monotonous ticking of the old wall clock seemed still in his ears, mixed with the smell of mothballs and aged paper. The things he had tried to bury with alcohol and forgetfulness were now roaring, breaking through the soil. "...The tools, I have them at home." He finally spoke, his voice hoarse. "The best magnifying glass, measuring rulers... and some comparison samples from back then... locked in a hidden compartment in my study." "You can't go back to get them." Lu Chenzhou said. "I know." Zhou Zhengping took a deep breath, standing a bit straighter, though his legs still trembled. "But I remember... those characteristic points. Pressure distribution, the curvature of the stroke beginnings and endings, the subtle breaks at the connections... I've looked at handwriting for over a decade. Some things, you can't forget." He looked at Lu Chenzhou, his eyes for the first time holding the sharp, focused light of an expert, though this light was wrapped in thick fear. "Show me what you need appraised. Now. Find a place with light." Lu Chenzhou stared at him for two seconds, then nodded. He pulled out a waterproof-sealed tablet from an inner pocket, turned it on, and called up high-definition scans of two documents. The screen's light illuminated the narrow space between them, also lighting up Zhou Zhengping's face, which instantly grew solemn and focused. The old man leaned close to the screen, squinting, his fingers unconsciously tracing shapes in the air, as if outlining the trajectories of those strokes. His breathing gradually steadied, his entire person entering a peculiar state of focus, incongruous with the surrounding dangerous environment. Far down the alley, car headlights swept past the intersection. Lu Chenzhou's back tensed slightly, his hand resting on the hard object at his lower back. But his gaze remained fixed on Zhou Zhengping's face, waiting for an answer that might pry open the iron curtain of a decade. Zhou Zhengping's finger stopped in mid-air. His brow furrowed, then relaxed, his lips "...The tools, I have them at home." He finally spoke, his voice parched. "The best magnifying glass, measuring rulers... and some comparison samples from back then... locked in a hidden compartment in my study." Lu Chenzhou didn’t speak. His breathing also grew quieter. "I know." Zhou Zhengping took a deep breath, standing a little straighter even though his legs were still trembling. "But I remember... those characteristic points. The pressure distribution, the curvature of the starting and ending strokes, the minute breaks at the linking points... I've looked at handwriting for over a decade. Some things, you can't forget." “Can you be sure?” “Give me paper and a pen,” Zhou Zhengping said. “I can draw a pressure distribution chart. The left document shows large fluctuations in the overall pressure curve. The writer was emotionally unstable, or… deliberately imitating. The right one has a steady curve, a long-formed writing habit.” Lu Chenzhou took a notebook and pen from his backpack. Zhou Zhengping took them and, under the light of the tablet, quickly began drawing curves on the paper. His wrist was steady, the lines clean and sharp, completely unlike the old man who had collapsed on the ground earlier. The scratching sound of the pen tip on paper was especially clear in the silent alley. The car headlights swept past for the third time. This time, Lu Chenzhou heard the faint sound of tires rolling over gravel. He stood up, walked to the edge of the newsstand, and leaned sideways to look out. At the mouth of the alley, the outline of the car was faintly visible. It hadn’t driven in; it was just parked there, the low rumble of its engine audible from dozens of meters away. “How much longer?” he asked, looking back. “Three minutes,” Zhou Zhengping replied without looking up. “I’m marking key points.” Lu Chenzhou walked back, his hand resting on the small of his back. His gaze shifted between Zhou Zhengping and the alley entrance. Time felt like stretched rubber, each second pulled taut. Zhou Zhengping finished the last stroke. He put down the pen and held up the paper. On it were two parallel curves, one fluctuating violently, the other gentle like rolling hills. “The left one is a forgery,” he said with certainty. “The forger’s skill is very high; the resemblance could be over ninety percent. But pen pressure can’t be faked. Muscle memory, emotional state, even physical condition on the day of writing leave traces on the pressure curve. This forgery… the writer was very nervous. He tried hard to control every stroke, but the more he controlled, the more unnatural the curve became.” He pointed at several peaks and troughs. “Look here, and here. In normal writing, pressure changes are smooth transitions. But here, abrupt peaks appear—this is when the writer suddenly applied more force, trying to make a certain stroke more ‘like’ the original. Overcompensation.” Lu Chenzhou took the paper. The curves looked like two ECG lines in the dim light, one chaotic, one steady. “Can it serve as evidence?” “Yes,” Zhou Zhengping said. “If the court allows me to use this analytical method. But more direct evidence is…” He pointed at the tablet screen. “The paper of the right document. Can you get the physical object?” “Not for now.” “Then find paper fiber samples,” Zhou Zhengping said, his speech speeding up as he entered an expert state. “Reimbursement forms used by government agencies ten years ago had specific paper specifications and batches. If the right one is genuine, its paper should match other forms from the same period that year. If the left one was forged later, the paper might not match. Even tiny differences—fluorescent agent content, fiber length—can be detected.” Lu Chenzhou put away the tablet and the paper. “That requires professional equipment.” “I know a place,” Zhou Zhengping said. “The old laboratory at the Provincial Judicial Appraisal Center still has some equipment. Before I retired… I had access. I don’t know if it’s still usable now.” “Too risky.” “Then what do you want to do?” Zhou Zhengping looked at him. “Handwriting analysis alone isn’t enough. You need a chain of physical evidence.” From the alley entrance came the sound of a car door opening and closing. Lu They moved forward along the passageway. It was piled with discarded construction materials, steel bars and wooden planks strewn haphazardly. Lu Chenzhou led the way, his flashlight off, relying solely on the faint light from distant streetlamps to navigate. The footsteps behind them hadn’t followed, but they hadn’t receded either. Those people had stopped at the mouth of the alley, seemingly observing, assessing. At the end of the passage was a rusted iron door, slightly ajar. Lu Chenzhou pushed it open a crack. Outside was a wider backstreet, with a few small shops still lit up—a barbershop, a hardware store, a closed fruit stall. A few electric scooters were parked across the street. A man squatted by the roadside smoking, the light from his phone screen illuminating his face. “Go out here, turn right, and walk two hundred meters. There’s a bus stop,” Lu Chenzhou lowered his voice. “Take the night bus to the East City Bus Terminal. Once you arrive, go to the third row of seats in the waiting hall. Under the leftmost seat, there’s a disposable phone. Use that to contact me.” Zhou Zhengping looked at him. “You’re not coming?” “I’ll draw them away,” Lu Chenzhou said. “You’ll blend in easier alone. Remember, keep your head down on the bus, don’t make eye contact with anyone. Get the phone at the station and wait for my message.” “What if…” “No ‘what ifs’,” Lu Chenzhou cut him off. “Your daughter can’t wait.” Zhou Zhengping fell silent. He glanced at the smoking man across the street, then at Lu Chenzhou, and finally nodded. Lu Chenzhou pulled a few small bills from his pocket and stuffed them into Zhou’s hand. “Bus fare. Go. Now.” Zhou Zhengping took the money, took a deep breath, pushed the iron door open, and walked out. His back appeared somewhat hunched under the dim streetlights, but his steps were steady. He didn’t look back. Lu Chenzhou watched him walk to the street corner, turn right, and disappear from view. He stayed where he was, counting to ten. Then he turned and began retracing his steps. When he reached the middle of the passageway, he stopped. From his backpack, he pulled out a palm-sized black device and attached it to the wall. It was a simple motion sensor, capable of detecting human movement within a five-meter radius. He set the parameters, turned, and continued walking. By the time he returned to the low wall behind the newspaper kiosk, he heard a sound—a faint scraping, like fabric brushing against brick. He crouched down, peering through a crack at the base of the wall. At the mouth of the alley, the car was still there. But now there were two more figures beside it, shining flashlights into the alley. The beams swept across the ground, over trash bags and stagnant puddles. Lu Chenzhou slowly retreated. His movements were light, his feet making almost no sound on the gravel. When he reached the iron door at the other end of the passage, he stopped, observing the street outside through the crack. Zhou Zhengping was gone. The smoking man across the street had also left, leaving only a scattering of cigarette butts. He pushed the door open and walked out. The night wind felt colder. In the distance came the wail of an ambulance siren, drawing near, then fading away again. Lu Chenzhou turned left and walked along the street, his pace neither hurried nor slow, like an ordinary person returning home late at night. After fifty meters, he turned into a narrow lane and suddenly accelerated. The sound of running echoed in the alley. He crossed two more lanes, scaled a low wall, rolled upon landing, got up, and kept running. The pain in his ribs returned, but he didn’t stop. Only when he reached a main road with streetlights did he finally pause, leaning against a wall to catch his breath. A faint vibration came from his pocket. He pulled out his phone. The screen lit up. It was an encrypted message from an unfamiliar number. Just two words: **“Arrived.”** Lu Chenzhou stared at those two words for three seconds, then deleted the message and put away his phone. He looked up at the sky. The eastern horizon was beginning to show a faint grayish-white. The night was nearly over. He turned and walked into a breakfast shop that had just opened by the roadside. A wave of heat hit him—the sizzle of fried dough sticks in oil, the hum of a soy milk machine, the dull thud of the proprietress kneading dough on the counter. He ordered a bowl of soy milk and two fried dough sticks, taking a seat in the corner. The When he got up to pay, the proprietress gave him another look. "Young man, your complexion doesn't look good. Been staying up late?" "Yeah." Lu Chenzhou took his change. "Got some things going on." "No matter how busy you are, you still need to sleep," the proprietress nagged. "You don't feel it when you're young, but when you get old, your whole body will ache with problems." Lu Chenzhou smiled faintly and didn't reply. He pushed the door open and stepped outside. The morning wind hit his face, carrying the unique, crisp chill of a city just before it awakens. He walked along the street, his pace neither hurried nor slow, merging into the gradually thickening flow of people. The phone in his pocket vibrated again. He took it out to look. This time, it was another encrypted message, even shorter, just one word: **"Sample."** An address was attached, in the old industrial district south of the city. Lu Chenzhou deleted the message and continued walking. His expression didn't change, but his steps subtly adjusted direction. At the next intersection, he turned right, heading towards the subway station. The morning rush hour hadn't started yet, so the subway station wasn't crowded. He bought a ticket, went down the stairs, and stood near the edge of the platform waiting for the train. A gust of wind came from the tunnel, followed by the roar of an approaching train. The train's lights pierced the darkness; inside the car, scattered passengers sat or stood, weariness from the early morning on their faces. The train stopped, the doors opened. Lu Chenzhou stepped inside and found a seat near the door. The train started, accelerated. The advertising light boxes on the tunnel walls blurred into flowing ribbons of light. He leaned back against the seat and closed his eyes. The pain in his ribs had settled into a persistent, dull ache, as if something deep inside was slowly hammering away. But his mind wasn't on the pain. He was thinking about that pressure distribution map. About the glint in Zhou Zhengping's eyes when he said "paper fibers." About the car parked at the mouth of the alley, and the person inside who hadn't gotten out. And that word. **Sample.** The train sped through the tunnel, swaying, roaring, heading for the next station. Lu Chenzhou opened his eyes and looked at his own reflection in the train window. That face appeared blurred in the flowing play of light and shadow, only the eyes were clear, deep as a well. He knew today wouldn't be any easier than yesterday. But at least, he now had a map in his hand. And an extremely fragile thread that might lead to the truth.