Oh Sang-man, the captain of Investigation Team 1 of the Seoul Metropolitan Police, who was sitting in the back of a brown van in the underground parking lot, turned his head at the sound of knocking on the window.

Four detectives were gathered next to the car.

Opening the door, Captain Oh handed out the investigation data he had in his hand to the detectives.

"Hurry up and read. Then prepare for the interrogation."

One of the detectives, who had been looking at the data for a while, looked up.

"Isn't Heogi-poong money launderer that Team 2 has been chasing for more than half a year?"

"That's right. I've got a definite situation that he's in the emergency room of this hospital."

"What's going on?

"Intentional gas explosion. Why would the wall of the cafe suddenly fly away in a win-win situation when the deal was over? He noticed the undercover detective. It seems like a contractors work."

Captain Oh lowered his voice and said, "No one is listening."

"As you can see from the data, this guy is not the end. Economic offenders, financial crime organizations, partners, etc. everyone is involved here. There's a lot of investigation. It's still January 1st, and you can just accumulate the year-end arrest results."

"Did Team 2 just hand over these golden eggs?

"What do you mean just? Captain Chun and three main detectives in the second team are in a coma. If you stop this important arrest opportunity because of the injured people, is that what a police officer should do?

A golden opportunity where he was justified in eating the results of other teams hard work. Captain Oh wasnt about to let this go.

"From now on, we will thoroughly interrogate and quickly identify the suspect. So that the commissioner can see the criminal's face as soon as he goes to work tomorrow morning. Understood?"

"Yes, sir."

"If you understand, follow me while reading the data.

Captain Oh got out of the van and stood in front of the elevator in the parking lot. He pressed the up button and waited, and the elevator door opened.

Inside, police officers from the local police station and Inspector Ahn Seok-young of the second metropolitan area accompanied a man.

"Detective Ahn?"

"Captain Oh."

"What's wrong with him? Did these gangsters do something crazy again?

Ahn Seok-young shook his head roughly pushing the desolate man wearing fixed protective gear around his neck forward.

"Hes the suspect behind the explosion of the cafe."

"What?"

All the detectives in the first team were wide-eyed.

"I'll be interrogating this person in the office, so please focus on searching for Heogi-poong."

Captain Oh urgently asked Ahn Seok-young, who was about to leave the parking lot.

"Hey, Officer Ahn. How were you able to get hold of him when you were with me? I'm sure he didn't turn himself in."

"The doctor at this hospital caught him and handed him over."

"Wh-who?"

Captain Oh thought hed heard it wrong.

"Then, I'll get going. Early morning interrogation is prohibited by the main office. There are only two hours left."

Captain Oh had no choice but to look at Ahn Seok-young like a dog whod been chasing a chicken.

At a time when Heogi-poong's case was taken over, forcing him to hand over even the arrested criminal was losing both justification and practicality.

As soon as Ahn Seok-young disappeared, Captain Oh said.

"How did the doctor catch the bomber from the cafe? You follow Ahn Seokyoung. Watch the interrogation and contact me right away if any information about Heogi-poong comes out."

"Inspector Ahn will probably hand over the important information on his own.

"How could he just hand it over on his own? If it were you, you would be deprived of the investigation you've worked so hard for months, but you'd be willing to help me well..

Captain Oh, who pointed out the fact that everyone was pretending not to know because he was embarrassed, coughed and got on the elevator.

"What are you doing? You're not going to get on?"

Inside the emergency room.

The man wearing a baseball cap gritted his teeth.

[T/N: Ill be calling him baseball cap from now on until his name appears.]

He failed to secure the laptop.

It was said that it was protected by high encryption, so that could buy time, but if the transaction was completed normally and automatically removed, this would not have occurred at all.

The baseball cap, who was fiddling with his cell phone to try to find another troubleshooter, quickly stopped moving when he saw two police officers passing by the bed.

"These days, gangsters don't seem to have a background. Are you sending your subordinates to a place full of police officers to warn rival organizations?

"That guy? Wasn't he a psychopath?

"No, the detective in charge said that."

The baseball cap's eyes flashed when he heard this.

It was the story of an organization fighting for influence with the Namyoung faction. Chunsik's sale, which operated a gambling house that used illegal lottery tickets as currency, was a place where the amount of money he wanted to wash was too small to be included in the transaction candidate list.

An organization that went this far might be the answer.

The baseball cap, which turned on the dark web's connector with his cell phone, searched for customer information and found the Chunsik boss' number.

[If you help me, I'll give you 1 billion won. 300 million won in advance]

By text, he presented all the money laundering fees to be obtained from the transaction. It was a waste when considering the value of keeping this business safe, but it was money that needed to be invested.

"Good job."

Someone approached the bed.

"I'm Oh Sang-man, the captain of Investigation Team 1 of the Seoul Metropolitan Police Agency."

The baseball cap looked at Captain Oh after manipulating his cell phone to show a messenger screen.

"Detective, did you catch the culprit who made the cafe like that?"

"We can't inform the general public in detail about the progress of the investigation, but we have some questions. Please answer sincerely."

"Right. I hope the culprit is caught soon.

Under the baseball cap, the man's face was covered with an innocent mask which said, I don't know anything.

Nurses walking in the hallway of the emergency center were surprised to see the size of the leader guarding the entrance of the medical office like a steel tower.

Muk-ho drew a full smile on his face so that the passers-by would not be surprised, but it only caused the nurses to walk faster.

The guy next to him shook his head toward Muk-ho.

"Brother, I don't think that's right."

"What?"

"When that face of yours smiles, people get scared."

"You punk."

A man in his mid-30s wearing a jacket with the phrase "cyber safety" on his back approached the two.

"Excuse me

Checking the name written on the door and checking the two men. The man tilted his head, as Muk-ho asked sharply.

"What is it?"

"Is Officer Yoon Joong-gi here?"

"Ah. Are you here to meet the detective? The person who specializes in forengi?

"I'm the forensics manager, Ham Sung Soo."

"That's right, forensics. I can only speak two languages, Seoul and Gyeongsang-do. But you can't just go in here. I need to be sure of your identity to get in, so show me your ID."

Click.

The door of the office opened and Yoon Joong-gi slapped Muk-ho in the back of his head.

"Are you crazy? Where is there a gangster checking the police ID card?

"It's because of the safety of our doctor. Isn't that player a mean guy who comes in with a disguise? I'm not a gangster today, but the doctor's right arm."

"Take care of your brothers, you guys. Sergeant Ham, please come in."

Ham Sung-soo, who passed between the men and entered the room, pointed outside with a surprised look.

"What are they doing?"

"The gangsters needlessly take care of loyalty. Don't worry about it."

Yoon Joong-gi sat in a chair and pointed to Dowook disinfecting the wound on his hand.

"This is Dr. Park Dowook that I mentioned earlier."

Dowook exchanged greetings with Ham Sung-soo after attaching the last band-aid to the back of the bruised hand while hitting the criminal's hard body without realizing it.

Yoon Joong-gi pointed to the table.

"The evidence laptop is over there."

Ham Sung-soo, sitting in front of the laptop, exclaimed as soon as he saw the screen.

"This is the famous coin blender.

"Coin blender?"

Ham Sung-soo, who felt the ignorance contained in Yoon Joong-gi's question, briefly explained.

"All transactions of large cryptocurrencies are open to the public. The anonymity of the parties to the transaction is guaranteed, but the anonymity of the transaction itself is not guaranteed. That coin blender is a currency mixing program that complements it, a kind of anti-tracking technology."

Ham Sung-soo, who was slowly looking at the information floating on the screen, soon opened his mouth and looked at Dowook.

"You tracked the flow of funds before mixing. If we work properly, it will take at least three nights and four days."

It was natural since he had the sense of the person who made it, but it seemed very surprising to that digital investigator. Dowook smiled awkwardly and quickly changed the subject.

"If we trace it back, can we definitely catch the culprit?

"Wait a minute."

Ham Sung-soo, who was tapping on the keyboard, sighed quietly.

"The blockchain archive on the Dark Web is the first trading point. Even if the wallet information of cryptocurrency is clear, it is too much to find it at once. Everything is encrypted.

Yoon Joong-gi couldn't keep up with all of the information, so he took out a notebook and asked.

"Can you decipher it?"

"It's possible if you run the program at the headquarters and get support from the cyber investigation unit."

"What information can you get?

"The bank account where the actual currency was injected, the IP of the access point, the date, something like that.

The account information alone was enough clue to identify the culprit.

Dozens of alphabets and numbers that look like machine codes.

Yoon Joong-gi looked at the place pointed at by Ham Sung-soo's fingertips for a long time, but he couldn't understand what it was at all.

"Even if it looks like a meaningless list, it's an asymmetric cryptographic system using a small number of RSA. Do you know Snowden? The person who exposed the CIA corruption. He also used this method to exchange information to avoid CIA tracking. Thanks to you, we have a decoding program."

Yoon Joong-gi, who was diligently writing down information in his notebook, asked.

"How long does it take to confirm with clues?"

"About 3 days"

"I need it done by tomorrow morning. You can't hold on to more people without evidence."

"Let's recruit a few more team members and shorten it as much as possible. Our team owes a lot to Captain Cheon, too.

Ham Sung-soo stood up and put the laptop in his bag. After bowing slightly to Dowook, he turned to Yoon Joong-gi and asked very carefully.

"How is the captain doing?

"He still hasn't become conscious."

"Oh my"

"Please. We have to catch him."

The forensics officer left and Yoon Joong-gi looked at Dowook.

"Doctor, I got a big clue thanks to you. Thank you so much."

"What? Hold on tight and put him behind bars. Can we arrest him with this?

"Yes, as long as we keep to the Miranda Rights."

Yoon Joong-gi looked at Dowook remembering what he said earlier and joking lightly with a grateful look.

Yoon Joong-gi, who came out of the hallway, bowed his head to Dowook one more time and disappeared toward the emergency center.

It's roughly finished, right? That fake intern, it was really creepy.

Dowook walked toward the lobby to return to the neurosurgery department and turned to the men following behind him. The two large men were following timidly.

"You don't have to follow me anymore. The police took the laptop."

Muk-ho shook his head.

"How can we do that? Woongman and I will be your right and left arm until the criminal is caught. It's a bad game where professional players are also put in, so who knows what would happen."

"That's right. We'll be the bodyguards."

Dowook eventually walked with two wings attached. Each doctor and nurse he encountered were busy getting out of the way.

Ding.

No one got on the elevator with them.

Dowook arrived in front of the office like that, continuing to feel like he had become the leader of a criminal organization for about three minutes.

Just before opening the door, Dowook looked back at the two behind him.

"Are you really going to stay here?

"Of course."

"You're not asking me to participate in the fight, are you?

"No. Absolutely not. But if we raise it to 2 million won, would you consider fighting.

"No."

When he refused at once, Muk-ho scratched the back of his head.

"I think you can get more than that, but I can't offer more than two because I'm just the fifth. If it were Sung-oh hyung-nim, he would have offered up to 3 million won."

Dowook entered the office and tried to close the door, but saw two people lined up side by side. Although they seemed fierce, he thought they werent that bad.

"Rest well, doctor."

The two bowed.

The neurosurgery hallway at 10 p.m. was dark. It felt a little weird to leave it there. Anyway, he wouldnt have been able to catch the fake intern without them.

"You can sit in the chair inside, but you have to be quiet. My exam is just around the corner."

"Can we do that? Of course. We'll keep our mouths shut."

"Come on in."

The two men stepped carefully into the office.

All kinds of surgical models displayed on one side of the wall. Among them, Muk-ho's expression froze when he saw the silicone head, which displayed the brain clearly.

"Oh man. What do you do here?"

"It's an office and a surgery practice room."

"Doctor, youre a really scary person."

Dowook asked Muk-ho, who seemed very scared.

"Do you know who owns this room?"

"You?"

"No. The big doctor hyung-nim."

In response, Muk-ho grabbed his neck and the cheek next to him reflexively.

Smiling Dowook pointed to one chair.

"Sit over there. The big hyung-nim left work, so you don't have to do that."

"Who is scared?"

"Oh? Professor Choi?"

When Dowook asked back toward the door, Muk-ho turned his back in surprise.

Of course, there was no one in the hallway.

"Please close the door since you turned your head."

Muk-ho's embarrassment,caused by Dowooks teasing, made his companion laugh.

"You're so cute today, Muk-ho hyung-nim."

"Hey. Shut up."

Under the protection of the two men who were crude but unexpectedly pure-hearted, Dowook resumed studying for his specialist exam which was disturbed by Seong Chang Soos emergency call.

About an hour later.

Although Dowooks head wasn't very tired, he couldnt help falling asleep because of his bodys exhaustion. He woke up at the sound of knocking on the office door.

When they turned their heads around, the two big guys had leaned their heads on each other and left for a distant dreamland.

Bang bang.

"Doctor! Dr. Park Dowook!"

It was an urgent voice.

Dowook approached the door without even yawning.

Click.

When he opened the door, Yoon Joong-gi, who was covered with sweat, stood in the hallway.

"Doctor, I'm in trouble."

As soon as Yoon Joong-gi saw Dowook, he told him shocking news.

"Officer Ham, who was returning to the station, was attacked. Fortunately, it happened near the main office, so he wasn't seriously injured, but the strongest evidence to catch the criminal It evaporated."

Dowook was speechless. Yoon Joong-gi spoke as if asking for help.

"It's clear that their purpose was the laptop, but just in case, please don't leave the hospital until morning. I'll apply for personal protection for you at the police station."

"There's no evidence at all?

"There are still clues that I wrote down to report to President Chun. I'll share this with the investigation team and catch it for sure..

Yoon Joong-gi, who was looking into the notebook, took a few deep breaths with a sad face.

From the cafe explosion to an investigator who cooperated in infiltrating a contractor.

There were too many things that a young detective could not handle at a time when Cheon Ho-beom, who had been at the center of the investigation, was in a coma.

"Why are you here again?"

Muk-ho, who woke up late, ran out in surprise when he saw Yoon Joong-gi.

"Did you catch the culprit?"

"Keep your loyalty to the doctor. I'll be watching you."

As soon as Yoon Joong-gi, who said so, was about to disappear.

"Detective. Wait a minute."

Dowook picked up his cell phone and pressed the call button.

-Dr. Park?

"Director, is there a formula that calculates a password? Do you know how to solve this?"

-More than 200 digits would be difficult in a short time.

"Detective. The code that Sergeant Ham mentioned earlier. How many digits are there in total?

When asked, Yoon Joong-gi began counting the alphabets written in the notebook with his fingers.

"45, 50. 54 digits."

"They said 54 digits".

-Then it'll take 20 minutes.

"Oh, really?"

-If we find it together, it might take 10 minutes.

"Then"

-Sounds good.

The answer came out first even before he could ask. This must be why her sister kept teasing her for being a Semdeok.

-Where should we meet?

"I'll go up."

Dowook, who finished the call, turned to Yoon Joong-gi.

"Can you photocopy that and give me a copy? There's a mathematician I know well, and I think she can solve it. Her skills are incredible.

Yoon Joong-gi was speechless at the moment.

A method to break through the blocked investigation again. Was there anything that the doctor couldnt do?