Taizai tugged at the collar of his trench coat twice to straighten his clothes. He motioned for Kokida to bring him to the warehouse.

Atsushi Nakajima hurried to catch up. When he brushed past Akutagawa, he heard the other party whisper,

"Don't cause trouble for an outsider."

He stopped and turned to look at Akutagawa. Akutagawa was also staring at him with an unfriendly gaze. This made him flinch a little.

Atsushi Nakajima swallowed and jogged a few steps to catch up with Taizai.

They walked from the new building to the warehouse located in the main building. Connecting the new building and the main building was a short corridor. The section near the new building was the permanent exhibition exit.

Atsushi Nakajima saw that the washroom near the exit was also cordoned off. Several police officers were rushing in and out to investigate something.

He was curious and couldn't help but slow down his pace.

"Ah, sorry."

Atsushi Nakajima was so engrossed in his thoughts that he didn't pay much attention to the front. As a result, he bumped into someone.

He looked up as he apologized, only to find that everyone had stopped in the corridor. He just happened to bump into Nakahara Nakaya, who waved his hand and smiled at him.

"Dun Jun." The Grand Chancellor called his name. "What are you thinking about? You look so lost in thought."

"Ah, nothing much."

He didn't need to look to know that Akutagawa's unfriendly gaze was on him again. This made him flinch a little. "Why are you all standing here?"

Taizai looked at him and laughed. "Because you seem to care a lot. I thought it would be interesting." He walked over and ruffled his hair. "Why don't you just say what's on your mind?"

"Ah, yes …" Atsushi Nakajima looked up at Taizai. "I'm thinking about what the police are investigating in the washroom."

Taizai turned to look at Akutagawa. The latter looked away and replied indifferently, "This is the washroom where Tachihara was found."

"Ah …"

Taizai glanced at Atsushi Nakajima, who almost said "I'm very curious" on his face.

"Let's go in and take a look."

That being said, only Taizai, Atsushi Nakajima, and Akutagawa went in. The washroom was not big. There were only four cubicles in total.

According to what the investigator said, Tachihara was found in the innermost cubicle. When the cubicle was locked, the police opened the door and found Michizo Tachihara, who was sitting on the toilet seat, unconscious.

"What?

Locked unconscious? "Atsushi Nakajima was in disbelief." Does that mean this is a secret room? "

"If you put it that way …" Taizai looked around. "But from the looks of it, the partition is attached to the ceiling and the floor. There is no gap in the middle. Tachihara was also locked inside. It can barely be considered a secret room."

Atsushi Nakajima walked into the cubicle and looked around. The washroom in the art gallery was actually quite small. It was just right for him. If there were two people, it would be too cramped to turn around. He looked around. There were no windows. There were only tile walls on both sides. There was a partition on one side and a door on the other. Now that the partition had been removed, how did Thief N lock Tachihara inside?

"Dunjun, if you have any ideas, why don't you tell me?" Taizai looked at Atsushi Nakajima, who was thinking hard.

"Mr. Taejae taught me before that there are generally four kinds of secret rooms," Atsushi Nakajima thought for a while and looked at Taizai's eyes. He slowly said as if he was encouraged.

"The first kind is an incomplete secret room. The criminal uses some method from the outside to hurt the victim inside. Although this kind of room looks like a secret room, there is a passage through which the crime can be committed.

The second kind is a complete secret room. The criminal does not leave the inside of the secret room after committing the crime. Instead, he hides in an inconspicuous place and takes advantage of the blind spots of the witnesses.

The third kind is a complete secret room. The criminal leaves after committing the crime and uses some method to send things like the door key back to the inside to form the secret room.

The fourth kind is a complete secret room. However, both the criminal and the victim are outside when the crime is committed. After that, the victim escapes into the room and uses methods like locking the door to form the secret room. The biggest difference from the previous few points is that the secret room is not formed by the criminal, but by the victim's initiative. "

After Atsushi Nakajima finished speaking, he let out a long sigh, as if to ease the tension from before. Unexpectedly, Akutagawa beside him suddenly spoke.

"There's a fifth kind."

He turned to look at Akutagawa, a little surprised. Akutagawa snorted and looked away to Taizai's direction. "The fifth kind is to use psychological misconceptions to induce the people present to believe that there's a secret room inside, but in fact …"

"Ah, yes!"

Atsushi Nakajima hit his left palm with his right fist. "I've seen this many times in cartoons. For example, the case where the older sister killed the younger sister, the older sister pretended that she couldn't open the door …" He realized what he had said and immediately stopped talking. Akutagawa, who was interrupted, naturally did not look happy. Taizai, who was beside him, had long been unable to hold back his laughter.

"Dunjun, which kind do you think it should be this time?" Taizai stopped laughing and looked at him.

"I think," Atsushi Nakajima looked inside the cubicle again. "It should be a complete secret room. In this case, the first and fifth kinds are eliminated. The second kind is also impossible. The criminal will commit another crime later. His purpose is that he doesn't want the real Tachihara to be discovered, so he won't stay in the cubicle and wait for someone to open the door."

"Comparing the three and four kinds, I think it should be the fourth kind."

Atsushi Nakajima said carefully. "The criminal injected Tachihara with an anesthetic when he wasn't paying attention. Tachihara, who sensed that something was wrong, entered the cubicle and locked himself in.

I think that should be the case. "

"Oh?" Taizai raised his eyebrows. "But what you said makes sense.

Akutagawa-kun, what do you think? "

"I …" Akutagawa was silent for a moment. "I think so too.

I can't imagine that the criminal could enter the cubicle and come out to form a secret room.

As for the toilet cubicle, there's no such thing as a key. "

"Central Plains Police," Taizai did not answer the two. Instead, he raised his voice and asked Nakahara Chūya, who was standing at the door of the bathroom, "Central Plains Police, what do you think Strange Thief N did?"

"I don't know," Nakahara Chūya answered without hesitation. "I agree with them."

"Is that so?"

Taizai's mouth curled up. He walked around the people in the bathroom and asked Akiko Yosano, who was standing against the wall, "Doctor Akiko, what kind of anesthetic was injected into Tachihara this time?"

"You won't understand the terminology. It's the kind that is commonly used in surgery."

"How long does it usually take for it to take effect?"

"I can't answer this question. It depends on the individual."

Akiko Yosano pondered for a moment. "Under normal circumstances, it takes about 715 seconds to completely lose consciousness."

The two people who heard this conversation lowered their heads and overturned their original thoughts.

It was almost impossible to inject a sufficient dose of anesthetic intravenously into Tachihara's body when he was conscious and able to move on his own. Furthermore, they had to make Tachihara choose to escape into the toilet cubicle and lock the door within 715 seconds …

Moreover, Tachihara was sitting on the toilet lid and sleeping soundly against the wall when he was discovered. If Tachihara struggled to lock the door and enter, he would probably lie on the floor of the cubicle.

"Then, could it be that the criminal placed the anesthetic in the toilet cubicle in advance? For example, where did he hide it? When Tachihara was using the toilet, he was inadvertently poisoned?"

Atsushi Nakajima thought for a moment and asked again, "Isn't there a novel where the criminal dissolves a highly toxic substance in the toilet and closes the toilet lid? When the victim returns home to use the toilet, he opens the lid and inhales the gas and is killed."

"Dunjun, there are three loopholes in your statement."

Taizai had gotten a pair of white gloves from the investigator and was slowly putting them on. "First of all, you said it yourself. The victim returned home, and this is the National Museum of Western Art."

"So …" Atsushi Nakajima didn't understand.

"The National Museum of Western Art is a public place with many tourists," Akutagawa explained. "The toilets here are cleaned by professionals. It doesn't make sense to hide something in the toilet. Even if the public toilet is decorated, it doesn't necessarily guarantee that it was Tachihara who was poisoned."

"In other words, the probability of Tachihara being poisoned is very small."

"Is that so? What's the other point?" Atsushi Nakajima asked.

"Tachihara was injected with anesthetic intravenously. The dose is not small. It's not an accident."

Taizai put on the gloves and clapped his hands. "But this is the first time I know that you're a fan of detective dramas."

Atsushi Nakajima scratched his head, embarrassed. "I'm just interested."

"Mr. Taejae, I have an idea too."

Akutagawa suddenly said, "Is it possible that after the prisoner anesthetized Tachihara, he locked the door of the cubicle, tore a hole in the partition, escaped to the next cubicle, restored the partition, and escaped from the next cubicle."

Taizai And Zhong stared at him together. After half a minute, Taizai said slowly, "It does seem like a method that you would consider. If you were the prisoner, in this case …" He walked into the cubicle and reached out to touch the nails on the partition. He shook the partition. "Akutagawa-kun, I don't know if you've noticed that there are four screws on each side of the partition. If the prisoner escaped to the cubicle as you said, how would he restore the four screws on this side?"

"… I didn't think it through."

"Mr. Taejae, you already know what's going on, right? Tell us quickly." Atsushi Nakajima looked at Taizai's smile and knew that he must have solved the mystery.

His words attracted a lot of people, and the police quickly gathered near the small washroom, blocking the door.

"I can't say that I've solved it." The Prime Minister touched the door panel that had been removed and put aside. "It's just a guess … Zhongyuan Police Inspector, can you do me a favor?"

Nakahara Chūya, who was called out, walked over. "What's the matter?"

"Please help me remove the lock."

"Huh?"

Everyone at the scene heard this and stared at the lock. Nakahara Chūya's expression did not change. "Compared to me, I think there are more suitable investigators."

"I think the Central Plains Police is the most suitable." Taizai narrowed his eyes and smiled.

"Again …" Atsushi Nakajima thought it was strange. Why was Mr. Taejae and the Central Plains Police so hostile? It was the first time they had met.

Chūya pursed his lips, took the tools from Taizai, and removed the cubicle's door lock.

The cubicle's door lock was not so much a door lock as a small latch.

Generally, the door locks used in the bathroom were either screw-on or insert-on, and the latter was used here.

Chūya removed the prismatic metal bar and handed it to Taizai. "And then?"

"And then …" Taizai weighed the latch in his hand a few times as if to confirm it. He smiled and handed it to Chūya. "Please stand behind the door with it."

At this time, Akutagawa realized something. "Mr. Taejae, you mean …"

"Yes."

Taizai asked for a magnet and stood on the other side of the door. He stuck the magnet on the door. Chūya released his hand, and the latch was firmly stuck.

Akutagawa took a step forward and removed the latch. He took out a small knife and peeled off the metal outside. Sure enough, a magnet was stuck firmly on the inside.

"Ah, so that's how it is!"

Atsushi Nakajima suddenly understood. "That's right. This kind of bathroom uses insert-on latches, and there's only a thin layer of metal on the outside. Thief N saw this and set up this cubicle in advance.

They used some method to bring Tachihara here, inject him with anesthetics, and leave. They only need to use a magnet to lock the door from the outside! "

"I think that's the case."

Taizai put the door lock into a transparent bag and handed it to the forensics team member. "What do you think, Central Plains Police?"

"Excellent." Chūya smiled at Taizai. "Excellent reasoning, Mr. Detective."

"You flatter me. It's just a coincidence." Taizai also smiled.

"But … it's that simple …" Atsushi Nakajima looked at the door bolt with a frustrated look on his face. "This setup is too simple. Anyone with a little common sense can do it."

"That's right." Taizai snapped his fingers. "This is indeed simple, but simple and effective."