The Murder Equation

At 21:30, Gang Taejun covered the names on the board.

Black tape covered the names of Hong Sanguk, Oh Sejin, Seo Ihyeon, and Yun Haewon. When the names disappeared, only the lines remained. Hand, order, silence, information input. The four lines were thinner than people, but they ran away less than people did. Looking at those thin lines, I breathed evenly for the first time.

"There are three experiments."

I said.

Gang Taejun did not pick up his pen.

"Are the experiment subjects people, or conditions."

That one question stopped my sentence. I had meant to say conditions, but the order of moving people was already floating in my head. Isolate Oh Sejin. Lock Hong Sanguk's access. I hand over the original. Put Yun Haewon in a different room. My words said conditions, but my movements were treating people like chess pieces.

Go Yura said in a small voice.

"If we start with people slots, we'll probably get it wrong again."

She was right. I drew a new table on the left side of the board.

`Condition A: Block the hand.`

`Condition B: Delay the order.`

`Condition C: Wake the silence.`

Only then did Gang Taejun pick up his pen. Beside each line he added `consent`, `record`, and `stop on failure`.

"If it's a joint plan, there are conditions."

"I know that."

"You haven't said them yet."

He did not accept my answer. Calling it a joint plan sounds good, but if I decide alone and explain afterward, it stops being an experiment and becomes an order. Gang Taejun knew where that order would go. His wrist moved a little slowly from an old injury. Still, the line he wrote was straight.

"First, we don't add a condition no one knows about."

He said.

"Second, we don't interpret a failure as a success."

Go Yura set down her pen tip. The small sound made everyone in the room pause for a moment.

"There's a third. We don't make anyone commit a crime they wouldn't normally commit just because of the experiment."

That was aimed at me. I didn't object. Part of what I'd been about to do sat exactly on that line. Making Oh Sejin unable to move, making Hong Sanguk frustrated enough to use another route, making Yun Haewon say something he didn't know he'd say. Then the loop reacts. The bigger the reaction, the bigger the evidence. I had been thinking about that size.

Gang Taejun slid the paper toward me.

"Distinguish between inducing and observing."

I wrote that sentence again at the top. `No inducement.` My fingertip stopped for a moment. Adding this rule would slow the plan down. Slower might mean losing people. But if we sped up without the rule, the point where we differ from Hong Sanguk would disappear.

At 21:45, we limited the first experiment to hands.

Oh Sejin had to stay outside the infirmary with the security team. The medicine cabinet would be sealed. Only a copy of Yun Haewon's emergency record would remain. No one would touch the original cartridge. That was as far as Condition A went. We deliberately left orders and silence untouched. That way we could see what changed when we blocked only the hand.

"Is this an experiment to save people, or an experiment to save a hypothesis."

Yun Haewon asked.

He didn't speak like a victim. It was the speech of someone treating his own death as a variable.

I couldn't answer right away.

"Both."

"If it's both, decide the order."

Gang Taejun said.

I wrote below the board.

`Protecting people comes before the experiment.`

My hand slowed while writing it. That sentence worked against me. An unfavorable sentence had to be the first line of the plan. That way, later, when I hide behind numbers, someone can point a finger at it.

Yun Haewon looked at the line and said.

"Then if I refuse, does the experiment stop."

"It stops."

Gang Taejun answered before I could.

I nodded late. The lateness itself needed to be recorded. The consent form included the phrase, `withdrawal possible at any time.` Yun Haewon pressed his finger against that phrase before signing.

"If withdrawing causes harm, who takes responsibility."

The room went quiet. A good question exposes the blank space in a plan.

"The investigation team takes responsibility."

Gang Taejun said.

"No."

Yun Haewon shook his head.

"The investigation team can't take responsibility for this. I'm a living person, and I'm the deputy director of this building. If I withdraw, write down the part I'm responsible for too."

Beside his own name he wrote, `Accepts liability for delayed public statement upon withdrawal.` The sentence was cold. It carried more weight because it was cold. He didn't just sit in the seat of a protected victim. Because of that, my plan wavered once again.

Go Yura prepared the logging device for Condition A. She didn't add more cameras. She made visible only Oh Sejin's hands, the cabinet seal, and the corridor access markers. Noeul messaged that she would leave the cup line by the cafeteria as it was. She now wrote down first that her own actions could become inputs.

`Didn't touch the cups today. If there's water on the floor, only marking it.`

Go Yura attached that sentence to the bottom of the table.

"I'll add it to the change input list."

Noeul's actions were no longer background. That fact alone changed the loop.

Gang Taejun printed out Noeul's text message in a separate envelope.

"Why turn even a text message into evidence."

I asked.

"Because we're the ones arguing that small inputs create big movements."

On the front of the envelope he wrote, `Voluntary notice, not a change in behavior.` It marked that we hadn't ordered Noeul to do anything new. The difference looked small. But later, if someone claimed the investigation team moved Noeul to produce a result, this small sentence would become a line of defense.

Go Yura wrote the same principle into the camera layout diagram. No new cameras would be installed. Only the storage range of the existing screens would be fixed. When the number of watching eyes increases, a person becomes a different person. We were trying to see the result left behind when a condition was blocked, not the result caused by a person changing.

At 22:20, we ran the preliminary loop of the first experiment on paper.

Gang Taejun demanded a paper-based route before moving actual people. I drew a diagram placing Yun Haewon in the waiting room beside the security office, Oh Sejin outside the infirmary, and Hong Sanguk inside the meeting room. The lines were clean. Too clean.

"In this diagram, what does Yun Haewon do."

Gang Taejun asked.

"He's protected."

"That's not an action."

Yun Haewon said without smiling.

"I have to survive and speak."

He wrote it into his own box himself. `Preparing testimony on the path of prior awareness of the R-3 possibility.` He wasn't a protected person, he was a person who would speak. The plan became a little less smooth. The less smooth version was the right one.

Hong Sanguk looked at his own box and said.

"Am I just sitting again."

"Yes."

Gang Taejun answered.

"That's confinement."

"No. If you don't agree to the access restriction, I'll request a written order banning terminal access related to R-3."

"Request it to whom."

"To the foundation auditor."

Lee Juwan raised his hand from the side.

"I'm not on anyone's side yet."

"That's exactly why I'm requesting it."

At Gang Taejun's words, Lee Juwan closed his mouth for a moment. Saying you're on no one's side is convenient. But in front of a document, you have to choose a position.

In the end, Lee Juwan wrote his own name at the bottom of the board.

`Legal observer, no involvement in experiment design.`

"That sentence is a shield too."

Go Yura said.

"That's right."

This time Lee Juwan admitted it.

"But you need a shield if you want to carry this record outside later."

I didn't like that statement. But it was correct. Evidence can't walk on truth alone. It needs the bridge called form. Hong Sanguk used that bridge very well, and we often missed it simply because we disliked it.

Gang Taejun wrote `Limited observer approval` beside Lee Juwan's sentence. Instead of asking about sides, he narrowed the role. Narrowing the role also reduces the size of any possible betrayal. I noticed myself doing that calculation. I was seeing people as slots again.

At 23:10, we moved Condition A into an actual route.

Oh Sejin sat in the chair outside the infirmary door. His hands stayed within the security camera's view. The cabinet key went into Gang Taejun's envelope. The envelope was transparent, sealed with two strips of tape. Go Yura aligned the camera time to an independent standard. She kept the central display beside it without merging the two.

"If we block the hand, the order remains."

I said.

"Don't write that sentence as if it's a result."

Gang Taejun cut in immediately.

I attached the word `expected`. Expected is not fact. Even an expectation that turned out right many times in the loop is not fact. We had already learned that in chapter 16, when the cart's movement was thrown off by Noeul's cleaning.

Gang Taejun made three blank boxes beside the expectation.

`Falsification conditions.`

I stared at the first box for a long time. Without a falsification condition, an experiment becomes a confession. It only becomes a device to confirm what I already believe.

Go Yura wrote one in my place.

`If the cartridge doesn't move even with Oh Sejin's hand fixed, the effect of Condition A alone is unknown.`

Yun Haewon filled the second box.

`If a different risk input occurs even with Oh Sejin's hand fixed, the protection has failed.`

I had to write the third one.

`If someone else moves, the hand-agent hypothesis is discarded or expanded.`

It took me time to write the word discard. Discarding a hypothesis I had built should be easier than discarding a person. But inside me, it was the opposite. I hated that fact.

As 23:55 approached, I looked at the recorder. We decided not to touch Condition C yet. The original was still in my hand. I didn't press the button. Not pressing it is also an action. I decided not to pretend not to know that today.

At 00:03, the sound of cart wheels came from the corridor near the infirmary.

Oh Sejin was sitting in his chair. Both his hands were within the camera's view. The cabinet remained sealed. And yet the cart moved. I tried to stand up. Gang Taejun raised his arm to stop me.

"It's moving within Condition A."

He signaled to only one security team member. If everyone runs, the input changes. Only one person moved. We watched the screen.

Only then did I realize my body had moved first. The first line of the plan was to protect people, but my first reaction was to secure the footage. If Gang Taejun hadn't stopped me, I would have gone out into the corridor. I might have grabbed the gray raincoat, or stepped on something that person dropped. I had nearly ruined the experiment I myself had designed.

"Seo Ihyeon."

Gang Taejun said without taking his eyes off the screen.

"Write down what you just did too."

I picked up the pen.

`00:03, observer Seo Ihyeon attempted to enter the scene. Stopped by Gang Taejun.`

That line was embarrassing. Which was exactly why it was necessary.

The cart didn't come out of the infirmary. It came out from the residence wing's emergency cabinet. That cabinet wasn't part of Condition A. Because I had only blocked Oh Sejin's hand.

The person standing by the cart wasn't wearing a white coat. They wore a gray raincoat. Their face was hidden in the shadow of a hood. In their hand was a cartridge with Yun Haewon's name on it. Same appearance. Different storage location. Condition A had blocked one hand and summoned another.

Go Yura zoomed in on the screen.

"That's not Doctor Oh Sejin."

She didn't swallow the end of her sentence.

The security team member stopped in front of the residence wing's emergency cabinet. The radio volume was lowered. Gang Taejun said, "Don't make contact, just confirm the location." The cabinet's seal was old. It wasn't a seal applied today. The residence wing's emergency cabinet used a different management log than the infirmary cabinet. I thought about why I hadn't added that log to the list.

The reason was simple. Because Oh Sejin was a doctor, I had only looked at the infirmary. I'd been trapped by the word medicine. I had heard back in chapter 25 that the cartridge could be medicine, or a record, or a name, and yet I had only locked the medicine slot.

"Condition A was too narrow."

I said.

Gang Taejun didn't nod.

"Judging it as narrow is a result. For now, write it as a scope omission."

His words were cold, but correct. The habit of attaching interpretation the moment a result appears. That habit too was part of the loop.

Gang Taejun wrote a new line on the board.

`Condition A failure: only medicine was blocked, but a different person moved the cartridge.`

I looked at that line, then looked back at the first sentence of the plan. Protecting people comes before the experiment. Which one were we actually looking at right now.

The gray raincoat's hand flipped the cartridge over. The label faced inward. Same direction as Oh Sejin's habit. But the hand wasn't Oh Sejin's.

The person on screen didn't put the cartridge in their pocket. They set it on the cart, turned the handle to the right, and stopped there. It looked less like an action to take something away and more like an action meant to be seen. But writing that it was intended to be seen would be jumping ahead again.

Go Yura froze the last frame.

"There's a bandage on the back of the hand."

"A medical worker."

Lee Juwan asked.

"A bandage isn't an occupation."

Go Yura answered immediately.

I exhaled a little late at that. To avoid repeating the same mistake, we had to stop the moment a small feature turns into a big identity.

The gray raincoat didn't leave after putting down the cartridge. The hand went back down below the frame. It pressed something. A new lock log for the residence wing's emergency cabinet appeared. There was no username. Instead, only a permission group was shown.

`Temporary emergency access.`

The moment Gang Taejun saw that line, his pen stopped.

"Oh Sejin's hand was blocked."

Yun Haewon said.

"So a different hand appeared."

I was about to write failure beside Condition A on the board, but I stopped. Failure was correct. But failure wasn't the end. Block one hand, and another hand appears. If that's true, then the first term of the murder equation wasn't the hand. It was the condition that chose the hand.

The person in the gray raincoat flipped the cartridge over once more, one last time. The label faced inward again. A second repetition. Too precise to be mimicry, too deliberate to be habit.

Gang Taejun spoke without turning off the screen.

"The next experiment isn't about adding more people."

He wrote a new sentence on the board.

`Find the condition that chooses the hand.`

Looking at that sentence, I understood where I had gone wrong. I had thought that if I blocked the person, the case would stop. The case had been choosing people to move all along.