Chapter Twenty – Where Does It Lead?

The phone’s shrill ring pierced the silence of the study.

Shen Mo pressed the answer button, and the voice of the municipal criminal investigation squad leader came through with a hint of suppressed urgency.

Over the past three months, five fatal falls had occurred. The victims were completely unrelated, yet they shared one common thread: they all died in the stairwells of old, state-owned residential buildings.

More precisely, they all died on the "thirteenth step" from the top.

The crime scene investigations were eerie: there were no signs of a struggle, and the footprints on the victims' shoes were perfectly aligned, as if they had been walking down the stairs normally before falling into thin air.

The autopsy reports pointed to a more baffling detail: at the moment of the fall, every victim’s muscles were in a state of extreme relaxation, as if they had no awareness of impending danger.

All the buildings where these incidents occurred were constructed in the 1980s as part of the same "South City Housing Project."

Shen Mo swiped his finger across his tablet, pulling up the case files. A crucial piece of information jumped out: every stairwell involved had used treads supplied by the same building materials factory.

He zoomed in on the crime scene photos, comparing them one by one. The survey data beside the photos showed that while the standard height for each stair should have been 17 centimeters, the measured height of the thirteenth step at every crime scene was consistently low, averaging only 14.3 centimeters.

Yet, the original architectural blueprints showed all data to be precise, with no record of construction errors.

A minor structural discrepancy, five human lives. This was no coincidence.

Shen Mo drove to one of the residential buildings, which remained cordoned off. The old stairwell was filled with a damp, musty odor, and the voice-activated lights flickered dimly. Avoiding the residents, he stood alone before the staircase that led to death at two in the morning, the hour when he would be least disturbed.

He took a portable laser rangefinder and a high-precision humidity sensor from his kit, fixed them to the wall opposite the thirteenth step, and began continuous monitoring.

Time ticked by, and the stairwell remained deathly silent.

Three hours later, as the humidity reading slowly climbed to 85%, a sudden anomaly occurred. On the display of the laser rangefinder, the reading representing the surface of the step began to fluctuate slightly.

Shen Mo’s pupils contracted. He watched as the wooden tread, having absorbed enough moisture, underwent a subtle, microscopic expansion.

But that wasn't the key.

The key was that at almost the exact same moment, a structural support beneath the step underwent an instantaneous deformation lasting only 0.8 seconds.

In those 0.8 seconds, the thirteenth step plunged exactly 13 centimeters.

A perfect "stumble trap."

When a person descends the stairs at a normal pace, their foot expects to land on a solid surface, but instead steps into a void that has appeared out of thin air. The massive height difference is enough to cause an instant loss of balance. Before the brain can even react, the body falls backward in a state of total relaxation, the back of the head slamming hard against the concrete step below.

Shen Mo put on gloves, took out a specialized sampling blade, and carefully scraped some wood shavings from the side of the step. Under the high magnification of a portable microscope, tiny, dimly gleaming metal particles were clearly visible within the gaps of the wood fibers.

He performed a rapid composition analysis, and the result made his heart sink.

Technetium-99, a rare artificial radioactive element, matched the residue he had previously detected on the mysterious cufflink and the ancient stone stele.

The clues once again pointed to the massive mystery lurking in the shadows of the city.

That evening, an unsigned, postmark-less letter appeared silently in the crack of his apartment door. The envelope was sealed with an obsolete type of bone glue, emitting a faint, fishy stench. The letter was written on traditionally crafted bamboo fiber paper, coarse and tough to the touch.

There was no text inside, only a severely yellowed black-and-white photograph. In the photo, three men in old-fashioned work uniforms were moving wooden planks in a dim warehouse. On the mottled wall behind them, someone had scrawled five words in thick charcoal: "Thirteenth step, leads to the abyss."

Shen Mo turned the photo over. On the back was a line of elegant yet forceful handwriting: "They didn't finish the walk, so the stairs will never stop."

He immediately dialed Su Wangying, briefed her on the situation, and asked her to use her clearance to help search the archives for building material companies related to the 1980s "South City Housing Project."

The next morning, Su Wangying called back, her voice heavy with gravity: "I found one. A lumber processing plant called 'Hongyuan Woodworks.' They supplied the prefabricated stair components for the housing project, but they went bankrupt in 1985. As for 'the abyss'… I asked a few retired construction workers. It was a nickname the workers gave to the factory's 'thirteenth-step inspection platform' behind closed doors."

Shen Mo hurried to the municipal archives. In the dust-covered construction logs, he found the key record.

"Hongyuan Woodworks" had been contracted for the stair projects of all the affected buildings in 1983. The log explicitly noted that the cedar wood used was from the "M8313" batch, which had been severely damp due to a warehouse leak.

A thought struck him, and he requested to review the death records from that year.

On October 7, 1983, the very day the first set of stairs was inspected and accepted, three inspectors fell to their deaths from a height. The official conclusion was "accidental fall after drinking," and the families received no compensation.

Three workers. The men in the photo were them.

At the end of the death record was another name—Chen Jianguo, the fourth worker in the group. He was the sole survivor, suffering partial memory loss due to a severe concussion.

Following the information in the files, Shen Mo found him at a nursing home in the distant suburbs.

The old man was no longer the sturdy worker of the past. He sat listlessly in a wheelchair, clutching a crayon, repeatedly drawing a distorted "13" on a piece of white paper, muttering incoherently: "The step… sank… it sank… we shouted, no one listened… no one listened…"

That night, Shen Mo and Su Wangying used an old map to find the original site of "Hongyuan Woodworks."

It had long since become an abandoned auto repair shop, the air thick with the lingering scent of oil and rust. Deep in the factory's underground warehouse, they discovered a forgotten, undemolished set of old stairs.

It was the original "Abyss"—the thirteenth-step inspection platform.

The thirteenth tread was rotten and broken, swaying precariously. Su Wangying took a damp cloth from her bag and carefully wiped the underside of the decaying wooden board. As the dirt was wiped away, three blurred fingerprints and half a line of nearly illegible charcoal writing stubbornly appeared: "We are here… remember us."

Shen Mo’s gaze sharpened.

He took out a matchbox-sized stress sensor and gently attached it to the support structure of the wooden board. The moment he prepared to connect the data cable, the device's screen lit up and emitted a piercing alarm.

Without any external load, the rotten step plunged a full 13 centimeters on its own, paused in the air for 0.8 seconds, and then silently returned to its original position.

Su Wangying covered her mouth in shock.

Shen Mo stared intensely at the data curve on the screen, which showed a sudden drop followed by an instant rebound. His voice was low and hoarse: "It’s not a malfunction… it’s a memory. This memory, soaked in despair and rage, was permanently recorded by the Technetium-99 and the damp wood. It is replaying."

As he spoke, the concrete ceiling above began to seep water droplets without warning. One drop, two drops… they gathered into a thin stream, dripping rhythmically onto the floor at their feet.

The sound was crisp and rhythmic, as if on the floor directly above them, an invisible person in heavy boots was walking slowly down from above, one step, one step at a time.

Exactly thirteen steps.

The sound vanished, and the underground warehouse returned to a dead silence.

But a greater storm was brewing in Shen Mo’s mind.

The sound was not an auditory hallucination; it was an echo of some kind of energy. He suddenly recalled the paper in the nursing home, the one Chen Jianguo had covered with the number "13."

The old man hadn't just drawn the number; next to every "13," there seemed to be an extremely scrawled symbol he had overlooked.

And in that dust-covered construction log, the record for October 7, 1983, besides the official conclusion, seemed to have a faint, pencil-drawn mark of unknown meaning in the margin.

Those two symbols, which he had dismissed as unconscious doodles, began to slowly merge in his mind.