6:12 a.m.

Daylight had begun to break.

But inside the SID Operations Room,
no one felt that morning had arrived.

The lights were still white.

The screens were still lit.

And the smell of coffee
was beginning to lose against the fatigue hanging in the air.

Dr. Cheng Kok Ming had only just returned to the forensic lab building
when the first preliminary test results came back.

Not a full report.

Only an initial one.

But sometimes,
the first teeth a case shows you
are already sharp enough to bite.

Sum Kwok Tong brought the report in personally.

He did not sit.

He placed the file on the table,
then pushed a transparent sample box beneath the light.

Inside it
was a minute residue sample extracted
from the fabric fibers at the cuff of Su Mei Mei’s outer sleeve.

No visible color.

No obvious smell.

And yet everyone in the room knew—

this thing
had already killed four people.

I looked at him.

“Shall we begin?”

Sum Kwok Tong nodded.

“Preliminary confirmation: this is not an ordinary commercial perfume composition.”

He opened the first page.

It was covered with chemical structure diagrams
so complex they looked like a maze.

“In terms of scent profile,
it does match several characteristics reported at the scenes. The opening carries a dry, green fig-leaf note. Not sweet. Almost brittle. The mid-layer has a bright orange-blossom lift, as if light itself has been suspended inside the volatile phase. The dry-down closes into a herbaceous woodiness—clean, restrained, slightly cold. And at the very end—”

He paused.

“There is a very faint white oleander trace.”

The room fell quiet.

Because what he was describing
no longer sounded like evidence.

It sounded like perfume criticism.

And the more it sounded like perfume criticism,
the more disturbing it became.

Someone had made a killing agent
with the craftsmanship of an artwork.

I lowered my gaze to the report.

“White oleander isn’t the point. What is?”

Sum Kwok Tong tapped the second page.

“The point is that these scent components are not simply layered together. They appear to have been designed to conceal some kind of volatile active molecule inside the fragrance structure.”

Lee Wai Hing looked up.

“Conceal it inside?”

“Yes,” said Sum Kwok Tong. “Like encapsulation. Like inducement. Like letting the human nose accept the fragrance first, and then carrying something finer into the nervous system.”

I lifted my eyes.

“You’re talking about poison?”

“I’m not calling it poison yet,” he said. “At least not only in the traditional sense. It behaves more like a neuro-disruptive molecular carrier.”

No one in the room spoke.

Because with that sentence,
the case had just risen another level.

A conventional toxin
kills a person.

This thing
seemed to first remove the person from themselves,
and only then decide whether to let them die.

Chang Hsin-Yan spoke slowly.

“So they sat down not because they were tired.”

“Most likely not,” Sum Kwok Tong replied. “More likely the vestibular system, balance, judgment, and light spatial awareness are affected first. A person feels dizzy. Feels they need support. Feels they have to sit down. But from the outside, it still looks like ordinary rest.”

In my mind,
the surveillance footage from the third case flashed again.

Tan Xin Yi walked to the pillar.

Paused for two seconds.

Then sat down.

No panic.
No chaos.

Too natural.

Natural enough to look like a decision she made herself.

But if it had never really been her decision—

then this was more than murder.

It was control.

I asked,

“What about dosage?”

Sum Kwok Tong shook his head.

“Not fully determined yet. But one point is already clear: this thing is extremely precise. The residue is minimal. It volatilizes fast. If ordinary field sampling is even a little slow, all that remains is the scent, not the structure. Which means the other side knows exactly what they’re doing.”

At that moment,
Dr. Cheng Kok Ming joined through the remote conference feed.

His face appeared on the side screen.

The background behind him was the forensic laboratory.

“One more point,” he said. “After comparing trace residues from all four cases, the similarity in core structural alignment is very high. Time differences, environment, and sample degradation created variation in each case, but the central molecular direction remains highly consistent.”

“The same formula?” I asked.

“More accurately, the same series,” said Dr. Cheng. “Like a prototype formula being continuously adjusted across successive versions.”

The entire operations room fell even quieter.

Successive versions.

What did that mean?

It meant the first case
had probably not been a finished product.

The second one
had not been either.

The third
was still being tuned.

And the fourth—

might only have come close
to the result they wanted.

I stood before the main screen,

looking at the four young faces.

They had not died separately.

They had been arranged in sequence,
station by station,
and led into the same experiment.

I turned.

“Chih Lin.”

Tan Chih Lin had already merged several data layers.

“I’ve got something.”

“Show us.”

He projected the victims’ contact histories
from the past three months,
divided into categories:

One, offline events.
Two, online forums.
Three, courier packages and free gifts.
Four, spending patterns.
Five, device-login overlap.

The lines were dense,
like a web.

“Let’s start offline,” he said. “Within one to three weeks before each incident, all four victims were exposed to high-end fragrance-related events. Not necessarily official large-scale launches. Sometimes boutique mall trial-scent sessions, campus co-branded sample giveaways, or small invitation-only experience events.”

Kim Min Jung immediately lit up the locations.

East City mall.
West City hotel boutique arcade.
University brand collaboration corner.
Pop-up fragrance display zone.

None of the places
were identical.

But the atmosphere was similar.

Carefully styled.
Refined.
Designed to lower suspicion.

“Now online,” Tan Chih Lin continued. “All four victims accessed several overlapping tech forums. Two of those forums looked like ordinary programming discussion boards on the surface, but hidden behind them were invitation-only channels. What’s strange is that in the past three months, those channels carried several ads that did not fit at all.”

“What kind of ads?” I asked.

“High-end perfume trial slots. Limited fragrance profile beta testing. Anonymous luxury sample box applications.”

Lee Wai Hing frowned.

“Perfume ads inside coding forums?”

“Yes,” said Tan Chih Lin. “That struck me as odd too. But of the four victims, three clicked through. Two filled in forms. One even received a package.”

“Which one?” I asked.

“Lin Bing.”

The screen changed.

Lin Bing’s courier record appeared.

The sender’s company name
was fake.

The logistics trail was complete,
but the shipment origin had been layered and washed repeatedly.

“What was the declared item?” I asked.

“Fragrance experience sample. No brand. Promotional gift.”

Chang Hsin-Yan stared at the screen,
her eyes colder now.

“This isn’t random net-casting. It’s contact first, then selection.”

I said nothing.

Because what she had just said
was already touching the same line in my mind.

At that moment,
Kim Min Jung projected a new set of synchronized surveillance composites.

“I found the common deployment pattern.”

Her voice was always level.

But this time,
even she had lowered it.

Four clips.

Four locations.

Four different environments.

She aligned them on the same relative timeline.

“Watch this.”

Case One,
East City University.

Thirteen minutes before the incident,
a person in a cap, mask, and pale jacket
walked slowly past the upper part of the stairway,
holding what looked like a flyer or a sample sachet,
and paused by the pillar for less than two seconds.

Case Two,
West City hotel.

Nine minutes before the incident,
a woman dressed like a hotel guest
passed the planter beside the stairway,
and made a faint downward motion with her wrist,
as if dropping something into a gap.

Case Three,
Yokoso Shopping Centre.

Eleven minutes before the incident,
a cleaner pushed a cart past the pillar,
the side of the cart stopped briefly,
then continued moving.

Case Four,
Taka Square.

Twelve minutes before the incident,
a person in a food-delivery uniform
moved quickly across the perimeter,
one side of the shoulder bag brushing past the pillar.

When the four clips ended,
no one in the room moved.

Because it wasn’t the same person.

Not the same face.

Not the same build.

But the motion structure
was nearly identical.

Approach the target point.

Pause briefly.

Complete some kind of deployment.

Leave quickly.

I spoke slowly.

“Different cover roles. Same operational logic.”

“Yes,” said Kim Min Jung. “They weren’t improvising. Each time they entered under the most reasonable identity for the scene: student, guest, cleaner, delivery rider. All roles that people don’t usually remember.”

Yim Bing stepped away from the map wall.

She pinned up a simplified deployment diagram.

“If this is a team,” she said, “then they operate in at least three layers.”

She marked the first point.

“Layer One: contact layer. Responsible for pre-contact—samples, fragrance trials, forum funneling, event-based filtering.”

Second point.

“Layer Two: deployment layer. Responsible for placement on site, putting the chemical carrier where the target will touch or pass through.”

Third point.

“Layer Three: observation layer. Watches from a distance, records the reaction, confirms the target enters the expected state, then withdraws.”

She paused.

“This is not a killer.”

“It’s a process.”

A process.

The word was cold.

Because process means maturity.

Maturity means rehearsal.

And rehearsal
means there may have been more than four.

I looked at the diagram
and said slowly,

“So these four cases are not four acts of impulsive murder.”

“No,” said Yim Bing.

“They are four rounds of experimentation.”

No one disagreed.

Sum Kwok Tong turned to the final page of the report.

“There’s one more thing.”

I looked at him.

“This fragrance carrier is highly sensitive to dispersal method. You can’t just spray it randomly and expect success. It may need to adhere to a particular medium first, then use environmental return flow, pedestrian movement, or short-range dwell time to enter the target’s inhalation range. In other words—”

“They don’t just understand chemistry,” I said.

“They understand space,” he answered.

“They understand crowd movement,” Kim Min Jung added.

“They understand behavioral inducement,” Chang Hsin-Yan said.

“They understand withdrawal,” Yim Bing said.

“And they understand how to leave almost nothing behind,” Lee Wai Hing finished.

The room fell silent.

Each of us
was sketching the same outline of the enemy in our minds.

Not a madman.

Not an opportunistic killer.

Not a street poisoner.

But a group
with knowledge,
procedure,
resources,
and patience.

I looked at the four cases on the screen.

The first
was a probe.

The second,
an adjustment.

The third,
a validation.

The fourth,
a formal presentation of the whole thing to us.

A cold feeling passed through me.

The other side was not afraid that we would know.

The other side knew—
we would eventually know.

And before we knew,
they had already moved to the next step.

I spoke.

“Put the conclusion on record.”

Tan Chih Lin’s fingers dropped instantly to the keys.

I dictated each sentence.

“This is not a set of isolated homicides.”

“This is not a lone-offender operation.”

“This is not a conventional poisoning.”

“This is an organized chemical assault test.”

Each sentence landed
like a door shutting.

Because once that door shut,
the case stopped being just criminal investigation.

It began to touch counterterror.

National security.

Cross-border actors.

The defensive line of an entire city.

Dr. Cheng Kok Ming watched me from the screen.

“If this judgment is correct, then the other side will not remain satisfied with four samples.”

“I know,” I said.

“They’ll scale the environment,” Chang Hsin-Yan said softly.

“They’ll increase crowd density,” Kim Min Jung said.

“They’ll make the deployment harder to trace,” Sum Kwok Tong said.

“They’ll switch to a carrier medium that’s even more difficult to follow,” Lee Wai Hing said.

“And they may start arming protection around the source of the experiment,” Yim Bing said.

I nodded.

Every one of us
was looking in the same direction now.

The city was waking.

But danger
had woken first.

I walked to the window.

Outside,
the sky had shifted
from gray
to a paler gray.

The first wave of commuting traffic
had begun to move.

The city looked normal.

Glass still gleamed.
The trains would still run.
Students would still enter classrooms.
Malls would still play music.

No one would know
that in the very air they breathed,
something had already been engineered
to near perfection.

It smelled like luxury perfume.

It arrived like coincidence.

It acted unlike poisoning.

And when it killed,
it did not look like murder.

I kept my eyes on the window and said quietly,

“They’ve already built the experiment into the city.”

No one answered.

Because that sentence
was already heavy enough.

I turned around.

“The next step is not asking who has died.”

I looked at them.

“It’s finding out who they plan to make inhale the next breath—when, where, and how.”

No one in the operations room relaxed.

Because from this moment onward,

this case
no longer allowed anyone to.