Chapter 1 — The Thirteenth Landmark

The survey boat got caught in a patch of duckweed so thick that the propeller made a dry sound. Minh An turned off the phone and looked up at the strip of newly built high-rise buildings across the river. The glass surfaces reflected the bright sunlight, looking like a completely different city from Ha Luu twelve years ago, where she used to sit on the doorstep and watch the water flood through the yard.

“If you keep pulling on the throttle, you'll wind all the water hyacinth into the shaft,” the boatman said.

An bent down and used the pole to push the green patch aside. She doesn't like being called "Miss" during technical meetings, but she also doesn't want to argue with the hired driver. From the moment he left the station, he told him three times that Tan Giang's RiverEye system was more modern than anything the city had ever had. The fourth time, An only replied with a yes.

On the control panel temporarily attached with a drawstring, the sensor screen showed a water level of 2.18 meters, stable for seventeen minutes. That data has been transmitted to the Ha Luu Urban Operations Center. An's task is very simple: check twelve measuring stations, compare the deviation with the standard mark, and sign the handover record before the system is used for a city-wide flooding drill on the weekend.

It was so simple that she planned to finish it in three days and then return to Da Nang, where her small apartment had an air conditioner that didn't make the noise of a ship's engine.

“Miss An, how far is station number seven from here?” the young technician sitting in front asked over his shoulder.

"Four hundred meters as the crow flies. But the canal has been flooded, so we have to go around the gate."

“Fade gate” is how the people of Ha Luu call the old regulating gates. On the digital map, this area only has a gray area called "expected infrastructure". The canal that once connected the ferry wharf to Can lagoon has been mostly filled in by the Tan Giang project, half of which is used as a temporary road, the other half is behind a row of corrugated iron sheets that are taller than people's heads.

An opened the paper map on his knee. The edges of the paper are soft because of the steam. She looked for the coordinates of station number seven, then realized that the number on the satellite map did not match the concrete landmark in front of her. In the bidding documents, the station location is 16.4723 degrees North latitude, 108.0121 degrees East longitude. The landmark in the field is off to the south by nearly thirty meters.

“Who set these coordinates?”

The technician returned. "Singapore consulting party. What's wrong?"

"It's okay. It's just that the landmark was moved."

An lies very naturally while at work. She placed her hand on the sensor body. New plastic, new screws, new inspection stamp. A perfect object lies in an imperfect position.

Twelve years ago, her father was convicted of opening the wrong outlet. The whole city calls him the man who brought water to the residential area. The verdict clearly states that he ignored the water level warning and arbitrarily changed the regulation order. An was nineteen years old when he heard the court read those lines. She did not understand hydrology, only understood that the neighbors looked at her mother with avoidance eyes, and her father never returned home.

It wasn't until he died in the prison hospital that An began to learn how to read numbers that could make a street sink.

The boat continues through the right door. On the right bank of the canal there are still dark cork trees, their roots clinging to the mud. On the left is a corrugated iron fence printed with the Tan Giang Infrastructure logo and the slogan: "Elevating the riverside city." Behind the fence, cranes are erecting towering steel frames. They call it a model urban area. The people of the North Shore call it the land taken from their graves.

An checks station number eight, nine, ten. The deviations are all within the level allowed, from 0.02 to 0.04 meters. She wrote down each number in the notebook, not immediately entering it into the tablet. That habit made her colleagues tease her for being backward. An doesn't explain that one loss of life is enough to turn a warning into a blank space.

Near noon, when the boat returned, the pressure gauge suddenly jumped to 2.31 meters and then dropped to 2.18. Changes take place in less than eight seconds.

“Sensor error?” the technician asked.

“Let it run again.”

“But the center just reported 2.18.”

"I know. Run again."

An took the handheld measuring device from the waterproof bag. The pressure needle stops at 2.29 meters. She asked the driver to keep the boat close to the shore, then manually drop the measuring line into the water. The actual water level is still nearly ten centimeters higher than the screen.

An error of ten centimeters does not kill anyone immediately. But in a regulated system, ten centimeters at one station can be half a meter in a hidden compartment. An took a screenshot and recorded the time: 11 hours 47 minutes 12 seconds.

Phone vibrates. The calling number has an Operations Center code.

"Miss Lam, I'm Nam. Is there any problem at station nine?"

Hoang Nam's voice was deep and steady, exactly like the person who read the flood warning news on television many years ago. An just met him this morning at the meeting. Nam is the deputy director of the center, in charge of data acceptance.

"Station nine is ten centimeters lower than the displayed number. I need to check the server."

“It's just network latency. RiverEye uses a median filter to remove noise.”

“The filter should not be allowed to clear an eight-second pressure peak.”

The end of the line was silent for a beat.

"I will ask a technician to check. Don't put your conclusions in today's minutes, wait for official confirmation."

"I haven't drawn any conclusions yet. I just recorded the measurements."

"I know. But the city is preparing for a drill. A note without context could confuse everyone."

An looked at the Tan Giang logo on the corrugated iron sheet. “An overlooked metric can also confuse people, just later.”

Nam did not answer. The call ended.

In the afternoon, An drove to the North Bank area instead of going to the hotel. The family's old house was sold a long time ago, but she still remembers the entrance through an alley with a leaning star fruit tree. Her mother sold tea at the ferry station, more than a kilometer away. An wanted to stop by, but she knew Mrs. Hanh would ask her if she was going to dig up her father's story again. That question will take both of you an afternoon.

An stopped the car next to the filled-in canal. A warning sign with a red background was erected on the lot: "Construction area, no entry." Behind the sea is a dirt road leading down to a narrow stretch of water. She saw what looked like an iron pipe sticking out of the reeds, with peeling white paint next to it.

Not understanding why, An stepped over the guard rope.

The canal bank was slippery, her protective shoes slipped twice. The iron pipe is chest high, the top end is covered with a moss green metal cap. On the body there are manual measurement lines and a number 13 stamped. Thirteenth water mark.

An touched the mud around the base of the pillar. No new traces. She opened the lid with a utility knife. Inside is a mechanical float, still moving with the water surface. The red needle is stopping at 2.47 meters.

An stood still.

The RiverEye monitor at noon read 2.18. The handheld recorded 2.29. Milestone 13 recorded 2.47.

She bent down to look closely at the clock face. Below the number 2.47 there is an additional line engraved by hand, deep and slanted: "don't trust the corrected number".

A sound rang out behind the corrugated iron fence. An turned around and saw the light The pickup truck's lights swept across the lot. The person in the car did not get out. The car backed up slowly, then disappeared behind a row of containers.

An took out his phone to take a picture of the watch, but the screen showed "no service". She turned on airplane mode and then turned it off again. Still no signal.

Before leaving, she discovered that underneath the watch face there was a small plastic slot big enough to fit her fingertip. An pulled out a tightly rolled piece of oiled paper. On the paper was the date of the flood twelve years ago and a series of six digits.

12.09 — 04:10 — 319742.

An recognized September 12. That was the day her father opened the floodgates.

Before she could grab the piece of paper, she heard the sound of metal hitting metal behind her. Someone was approaching from the dirt road.

An stuffed the piece of paper into his pocket, closed Milestone 13 and ran towards the car. As she opened the door, a man's voice rang out in the middle of the reeds:

"Miss Lam Minh An, right? Don't turn a scrap device into a big deal."

An turned his head. The man wore a white shirt, standing about ten meters away from her. The face is unremarkable, only the arc-shaped silver ring on the index finger.

“Who are you?”

“He wants you to complete the contract on time.”

“Then you should talk to the Operations Center.”

“I'm talking to someone who can make the contract disappear.”

An did not reply. She closed the car door, locked the latch and started the engine. The man did not chase, just stood and watched her retreat into the street.

In the rearview mirror, the number 13 on the iron pillar became smaller and smaller, obscured by fences and reeds.

An drove straight to the ferry terminal. She called her mother for the first time in four months. Ms. Hanh picked up the phone on the sixth ring.

“Are you back?”

“Do you ever know an old water mark in the canal behind the Tan Giang project?”

The other side was silent. The sound of boiling water and a customer ordering tea entered the phone.

“An,” Mrs. Hanh said, “where are you standing?”

“North Shore.”

"Get back here now. Don't talk on the phone."

“Do you know Milestone 13?”

“Mom told me to come home right away.”

An looked at the row of houses across the river. The sun is still shining, the streets are still dry. But for the first time since returning to Ha Luu, she felt like the city was holding its breath.

In his pocket, a piece of oiled paper rubbed against the zipper. The six-digit number burned like an unopened message.