Chapter 1 — Calls are not allowed to be hung up

— Honey, honey, he's not breathing anymore!

The woman's voice in the headset screeched, mixed with the loud sound of motorbike horns and the sound of someone shouting her name. Vu Khanh Dan gently squeezed the receiver, her eyes still glued to the left screen where the call location was flashing a red dot on the map at 47 Le Trong Tan Street.

— I hear you, calm down. Are you standing near the victim?

— That's right, that's right, he's lying right here, bleeding, bleeding a lot...

— Look closely for me, does his chest move up and down?

The other end of the line was silent for a second. Dan counted her own breathing to keep her voice even, neither fast nor slow, just like she had done with every call for eight years, even though inside her chest her heart had never slowed down.

— No... honey, I don't see anything.

— Okay, listen to me carefully. The ambulance is on its way, should be there in about seven minutes. In the meantime, I need to help you with something very important.

Dan looked to the right screen and quickly typed a dispatch command. The blue cursor of ambulance 115-07 was flashing and moving on the map. She reached out and pressed the button to relay the information to the field medical team's channel, all in less than three seconds, an action she had repeated thousands of times to the point where her fingers found the right key without looking.

— She placed her hands on top of each other, between his chest, just below his sternum. Press down hard and then release, about twice per second, like you're counting along to "Happy Birthday".

— Oh my god, baby...

— You can do it. I'm here, I won't hang up, just keep pressing, one, two...

Dan's counting echoed steadily in her headphones, and she heard the woman's breathing become more rapid with each chest compression. There was the sound of another motorbike horn coming, the sound of people gathering, the sound of someone shouting "get out of the way, get out of the way and let her do it". Dan didn't take his eyes off the countdown clock on the corner of the screen. Six minutes. Five minutes and thirty seconds.

— Thirty, take a break, tilt the victim's head back, cover his nose, and blow two breaths into his mouth for me.

A series of chaotic sounds, then the woman's voice choked:

— He... he coughed, honey, he coughed!

— Very good, let him lie on his side with his head slightly tilted back, the ambulance is almost here.

Thirty seconds later, the sound of a siren echoed through the phone, mixed with the woman's sigh of relief. Dan held the line for another minute until he heard the emergency technician's voice confirming the patient had been reached, then gently ended the call. She removed the headset from one ear, letting it dangle, and let out a long breath through her teeth.

The 115 Emergency Center at seven o'clock in the evening was still as bustling as during the day. The on-call desks were arranged in three rows under cold white fluorescent lights, each desk had two gently curved screens, one displaying voice frames and call records, the other displaying a navigation map with red and blue dots moving slowly like a school of fish in a glass tank. The phone rang continuously somewhere at the back of the room, interspersed with the incessant clicking of the keyboard.

On the front wall, a larger screen divided into four panels displays the number of calls waiting, the number of ambulances in operation, and a general map of the entire city with hot spot clusters colored by call density over the past hour. Each twelve-hour shift, the operator takes turns leaving the desk for five minutes to drink water or go to the bathroom, but the headset is never out of reach, placed on the desk like a temporary body part that can be removed and then reinstalled.

— The song just now is so sweet, Ms. Dan.

Ngan Bao Ky sat at the next table, took off his headphones, and turned his chair around a little. He was twenty-four years old, just over a year into his career, his face still had the eagerness of someone who was not used to hearing dozens of panicked voices every night.

— It's not sweet, just lucky. The reporter was calm and knew how to do chest compressions properly because she had studied first aid at the company.

— Yet you still count every second, making me think your heart beats too.

Dan laughed softly, reached for the water bottle placed next to the keyboard, and took a sip. She glanced at the shift statistics screen. Up to now there had been eleven calls, three of which were real emergencies, the rest were asking for directions, calling the wrong number, or a drunk old man calling to... ask for the time.

— Once you get used to it, you will realize that not all panicked voices are dangerous, but overly calm voices are sometimes worrying.

— Oh, why is that?

Dan did not answer immediately. She looked towards the team leader's desk, where Than Anh Tuyet was bending down to check a printed statistical table, his glasses hanging down on the bridge of his nose. Twenty years in this position, Ms. Tuyet was the only person on the night shift who directly trained Dan in the early days, and was also the only person who had never asked Dan directly about what happened five years ago.

— Because people who are truly in danger sometimes have to try to keep their voice as calm as possible, so that someone doesn't hear them calling for help.

Bao Ky frowned and was about to ask more when his desk phone rang. He quickly put his headphones back on and turned towards the screen. Dan glanced at the clock on the right corner of the screen, seven twenty-three minutes. There are nearly twelve hours left before the shift ends. She turned around, rearranged the small stack of notes next to the keyboard, a habit she had kept for eight years: every suspicious call, whether it ended smoothly or not, she recorded a few lines, the time, the background sound, her own feelings. Not because of mandatory procedures. Just because once, a long time ago, she failed to record an important detail in time, and that detail disappeared along with a human life.

She pushed that thought out of her head with familiar movements: stretching, rotating her wrist, checking to see if the headphones were plugged in securely. It was a small ritual she set for herself every time old memories threatened to surface in the middle of a shift, a way to bring herself back to the present, to the numbers flashing on the screen, to the breathing of the person waiting on the other end of the line.

In his desk drawer, under a stack of shift report forms, Dan kept a leather-bound notebook with frayed corners. No one in the on-call room had ever seen her open it in the middle of a shift, but every night before signing the handover book, she spent exactly two minutes recording the calls that made her nervous. Some months the notebook is only one page thicker, other months it is ten thicker. Bao Ky once jokingly asked what diary it was. Dan just laughed and said it was a list of questions she hadn't yet asked.

Nine o'clock in the evening passed with the usual regularity: an old man having difficulty breathing due to asthma, a case of food poisoning at a nightclub, two false alarm calls from the same number that the switchboard was familiar with. At ten o'clock, the on-call room was a little less noisy, the fluorescent lights were still cold white as before but there was a feeling of calmness following the slow breathing of the whole room.

At ten forty-seven, Dan's phone rang.

She picked up the phone reflexively, her voice was steady and familiar:

— Emergency hotline one year, please listen, what do you need?

There was no immediate reply. There was only a thick silence, different from the silence of a wrong number call or a call that was cut off midway because of weak signal. Dan clearly heard the sound of very small, very rapid breathing, as if someone was trying to hold their breath so as not to make any sound other than the words they were about to utter.

— Hello, the operator is here.

A child's voice, so small it was almost just wind, whispered close to the microphone:

— Auntie... save me...

Dan immediately sat up straight, raised his left hand and quickly typed on the keyboard to turn on priority recording, his eyes glued to the navigation screen loading the rotating circle that had not yet displayed the coordinates.

— I heard you, where are you? Just speak slowly...

— I can't... I can't say it out loud...

There was a very soft sound behind that voice, like the sound of a wooden door rubbing against a frame, and immediately the child's voice stopped. Dan held his breath, his whole body tensed like a guitar string, only the sound of his heart beating in his eardrums could be heard.

— My child...

Tut. Tut. Tut.

The line has been disconnected. The navigation screen was still loading, the rotating circle had not yet given any coordinates, and the caller number that appeared on the screen was just a series of strange numbers, no name, no registered address, as if it had never existed until just a moment ago.

Dan sat motionless for exactly three seconds, the headset still close to her ear, the steady beeping sound signaling the end of the call still echoed somewhere in her head, longer than the silence just now.

Then she pressed the callback button. One ring, two rings, three rings. No one picked up the phone. On the sixth episode, the automated operator's voice rang out monotonously: "The subscriber you have dialed is currently unreachable." Dan hung up and tried again, the result was the same. She pulled the mouse and quickly opened the call log. The display time was exactly nine seconds, too short for the station's positioning system to lock in an exact coordinate. The pale yellow circle still hangs on the map, not shrinking, not disappearing, just standing there like an unanswered question, covering an entire area of wards so large that it is meaningless.

Dan took off her headphones, put them on the table, and for the first time in eight years of working, she felt her hands shake a little.