Wang Chao moved fast.

When Zheng Xiaoming’s parents walked out of the portrait room with their son feeling dizzy, the little chubby kid was snatched away by a scary teenager running towards them.

Lin Chen held back Zheng Xiaoming’s parents and gently said, “They may have some problems that need.. private communication..”

Zheng Xiaoming’s parents were confused, so Lin Chen had to invite them to the rest area and make two cups of tea for them.

Through the glass window, they could see Wang Chao facing Zheng Xiaoming and having a conversation that was incomprehensible to the latter. Wang Chao kept talking while Zheng Xiaoming looked up with a confused expression as if he couldn’t understand what he was talking about.

Seeing the two of them, the surrounding police officers surrounded them curiously.

“Xiao Wang Chao, are you speaking Chinese? Why can’t I understand a single word?” a nearby officer joked. “The little guy will faint because of you.”

Wang Chao glared at him and waved his hand. “You mortals, don’t disturb our communication!”

After a moment, a very strange scene happened. Comrade Zheng Xiaoming pulled Comrade Wang Chao and sat on the office chair filled with cushions. He faced the computer in front of Wang Chao without feeling intimidated and typed a few Chinese characters, and then a large number of high-rise building images appeared. Zheng Xiaoming looked at one of the buildings, took a piece of paper, wrote down a string of numbers, then obediently jumped off the chair, put his hands on his stomach, and looked up at Wang Chao again.

“Are you sure?” Wang Chao asked.

Zheng Xiaoming nodded.

All the police officers around them surrounded them, but no one dared to speak.

Wang Chao howled and quickly jumped into the chair to operate the computer.

Lin Chen nodded to the two adults in the rest area and walked to the crowd.

Several police officers made way for him, and Lin Chen stood behind Wang Chao’s office chair, with the chubby boy quickly rubbing against his leg.

Lin Chen had never understood Wang Chao’s computer interface. The young man typed a long code and then turned around to see a large crowd of people behind him. He said in horror, “What are you all doing around me? It’s so scary!”

“I heard that the murderer tied the murder weapon to a balloon and released it?” one officer asked.

“I heard that you are planning to retrieve the murder weapon?” another officer asked.

“We’re here to see you act cool,” a third person said.

Wang Chao cursed and was then slapped by Xing Conglian on the head. “Speak properly. How are you going to find it?”

“The most primitive search method is to cast a net over the entire city. We’ll put out the news, determine the final location of the balloon based on witness reports, and then judge based on the direction of the wind that day. As long as the murder weapon hasn’t fallen into the water or been picked up by some auntie who washed it and is using it to chop vegetables, it can always be picked up by the public or searched by us. It’s just a matter of time, right?”

“Cut the nonsense,” Xing Conglian said, seemingly annoyed.

“I have a faster way. I can calculate the approximate landing point of the murder weapon and narrow down the search area to the size of five football fields. If everything goes smoothly, we can find the weapon before dark today!”

“Explain,” Xing Conglian said.

“Well, in meteorology, there is a mathematical model specifically for finding the landing point of meteorological balloons and baskets after they are cut. We can use this model to determine the possible landing range of the murder weapon after the balloons pop in the air.”

“But how do you determine where the balloons pop? There are too many possibilities—from the gas inside the balloon, the weight of the weapon, and the material of the balloon’s surface—they all have a significant impact.” Xing Conglian paused and asked, “Do we need to conduct experiments?”

“Boss, this is also a primitive way of searching. Of course, we need to conduct experiments.” Wang Chao grinned. “Xiao Ming’s mother said that the balloon the murderer gave to Xiao Ming was the kind sold in the amusement park. So we will also buy a few, tie them with weights and fly them, and use this to find the possible landing point of the weapon. Here are the calculations my friend just made about the weight of the tool,” the teenager said, handing over a bunch of values written by the little fatty just now.

“What the hell is this?”

“Oh, my little brother just calculated the weight of the object tied to the balloon. That’s the possible weight range of the weapon.”

Lin Chen looked at the numbers on the paper and asked, “How did you calculate this?”

“High school physics and estimation. I just taught my little brother in class just now, and he understood it. Impressive, right?”

Lin Chen frowned and looked at Wang Chao skeptically, “Really?”

Wang Chao felt embarrassed by the gaze. “Uh..I just wanted to see if he could understand it. In fact, there are not many knives that can be lifted by three balloons and still be able to kill people. They must be light and sharp, and I just asked the forensic department. They have determined the type of knife. I just had my little brother calculate it using physics as a reference. In fact, these weight errors can be ignored when they are in the air.”

“So it was just for show?” Lin Chen looked at the chubby kid next to Wang Chao and was speechless.

Xing Conglian took the paper handed to him by Wang Chao and ignored the teenager’s constant reference to “my little brother”. He waved his hand and asked the officers to arrange an experiment at the amusement park lakeside.

The crowd around Wang Chao’s computer reduced by one-third.

Wang Chao shouted loudly at the departing officers, “Remember to install GPS up there!”

Xing Conglian twisted his neck back to the front of the computer, and continued, “The experiment is okay, but the wind speed changes every day. What is your solution to cover all possible scenarios?”

“Boss, now I’m going to tell you about another search method,” Wang Chao said excitedly. “You just said that the difficulty in calculating the final landing point lies in the time when the balloons pop in the air, and there may be multiple cases where one or two balloons pop, so the trajectory will be very erratic. So, how can we calculate the erratic trajectory of the balloons?”

Comrade Xiao Wang dragged out his tone, but no one paid attention to him. He had to increase the volume of his voice and answer himself loudly, “Radar.”

“That’s impossible,” Xing Conglian said. “How could such a small balloon and its attachments be detected by radar? Meteorological balloons can be detected by radar because they are 10 to 20 times larger than normal balloons in size.”

“Have you heard of airport bird detection radar?” Wang Chao asked in return.

“Go on,” Xing Conglian stopped talking.

“All radars are the same. I won’t go into the specifics of the principle. Commonly used moving target radars can detect high-speed moving targets while suppressing fixed useless targets such as buildings, mountains, and clouds. However, they cannot identify small reflective cross-sections and low speed moving objects. In order to detect and filter low speed flying objects with small reflective cross-sections through radar, an improved filtering algorithm is needed, which is worth tens of billions.”

Xing Conglian gave him a glance. “Your A’Chen Gege has been listening to your nonsense for ten minutes here, so there’s no condition for negotiation.”

Wang Chao deflated and could only suggest, “Let’s go to the Civil Aviation Administration and request the radar data from yesterday’s incident. I’ll filter it, but the algorithm is not for sale.”

The time they found the murder weapon was not too far off from Wang Chao’s estimate. The police could always manage to find what they were looking for, barring any unexpected circumstances.

Before that, Lin Chen had been sitting in the lounge, not saying much, and had refused Xing Conglian’s offer to take him to the hospital. He sat barefoot on the couch, watching everyone in the police station busy at work.

Zheng Xiaoming was sitting next to him, doing his homework. The parents of the chubby boy still had to go to work in the afternoon, but since their child refused to go back to school, they had no choice but to leave him at the police station.

Lin Chen watched the little boy grip his pencil tightly with his fleshy fist, writing Chinese characters stroke by stroke in his notebook. The thing about geniuses wasn’t that they were scary; it was that they had strong willpower, which could basically destroy the earth.

When Xing Conglian came in for a break, Lin Chen was patting the little boy’s head, telling him to study hard at school.

“I thought you would suggest to his parents to send him to a class for geniuses to be with his peers.” Xing Conglian handed him a cup of warm water.

“Is there such an elementary school in Hongjing?” Lin Chen asked.

“Uh..” Xing Conglian squeezed in beside him and smiled. “Why don’t we start one?”

Lin Chen held the cup of water and smiled.

“Your smile seems forced, Consultant Lin,” Xing Conglian said. “It’s not like the kind of smile that sweetens my heart when I see it.”

Lin Chen didn’t respond to the joke.

“Since we found out that the suspect released the weapon, you haven’t said much,” Xing Conglian finally said.

“It’s not that. It’s just hard to explain.” Lin Chen took a sip of water. “I still feel like it’s an unnecessary thing to do.”

“Hmm?”

“Using balloons and releasing the weapon. The target is too big. Would a savvy killer do that?”

“It’s hard to say. It depends on the killer’s personality. Some are born with twisted minds and get extremely excited after killing someone, even wanting to strip and dance,” Xing Conglian said.

“Yeah, that’s why I think it’s difficult to explain this matter clearly.” Lin Chen shook his head. “If he is a professional killer, he shouldn’t be unaware that the police would find the discarded murder weapon. If he did it purely to get rid of it quickly, I can understand. But I can’t understand why he didn’t tie the last balloon to the weapon and instead took it with him to give to Xiao Ming.”

“There is a theory that murderers should quickly release the evidence related to their crime in batches, but it’s not reasonable to explain why he gave the balloons to Xiao Ming.”

Lin Chen didn’t know what to say. In the end, he could only tell Xing Conglian, “I think there’s nothing for me in this murder case, so I have to find some meaning for myself.”

Xing Conglian said seriously, “Blame Wang Chao for being too capable. I’ll go back and beat him up.”

Upon hearing this, Zheng Xiaoming, who had been doing homework all along, looked up with a frightened expression and shifted his butt to the other side of the chair.

This was so cute that Xing Conglian went over and kissed the little boy’s face.

Zheng Xiaoming and Wang Chao were probably similar in some ways. After Xing Conglian kissed him, Zheng Xiaoming stood up without saying a word, walked to the tissue box, took out a tissue, folded it neatly, and carefully wiped the spot where Xing Conglian had kissed him on the cheek.

Xing Conglian was stunned.

Just then, there was suddenly an excited celebration outside the lounge.

Lin Chen and Xing Conglian looked at each other.

A police officer rushed in and shouted, “Captain, they found the black bag!”

“So fast?” Xing Conglian stood up, surprised.

“It happened to fall on a lawn in the suburbs, and it was very conspicuous. Xiao Wang calculated the address, contacted the local police, and they used a metal detector to find it right away.”

About forty minutes later, the black plastic bag and the murder weapon wrapped inside it, along with the remnants of the burst balloons and ropes, were delivered to the Hongjing Criminal Investigation Division.

Because the process of finding the weapon was so exciting, most of the forensic department and forensic doctors had gathered around by the time the evidence was delivered.

The black plastic bag was carefully unpacked layer by layer, finally revealing the silver-white, blood-stained blade inside.

Everyone present breathed a sigh of relief.

Xing Conglian stepped back and said, “Let’s get to work. First, let’s confirm that this weapon was used by the suspect.”

Samples of blood on the blade were extracted, and the forensic doctor began examining the fingerprint traces on the plastic bag and transparent tape wrapped around it.

When the test results came out, Lin Chen and Xing Conglian were eating in the cafeteria with Wang Chao and Zheng Xiaoming.

Zheng Xiaoming preferred the braised chicken legs cooked by the chef at the police canteen. To show his good virtue of brotherhood, Wang Chao made an exception and bought five chicken legs with 30 yuan from his small coffers and gave them all to Zheng Xiaoming.

Lin Chen watched as Zheng Xiaoming had already eaten three whole chicken legs and was preparing to eat the fourth. He felt that this wasn’t good, so he quietly moved the dish to a place where Xiao Ming couldn’t reach it, in front of Xing Conglian.

Xing Conglian glanced at the fingerprint report and asked in surprise, “The fingerprints on the tape and the notebook I brought back from Tan Kang’s office are from the same person?”

“Yes,” the officer nodded, and he handed the second piece of paper to Xing Conglian. “Then we analyzed the blood sample on the knife and confirmed that it belonged to the victim, Tan Kang.”

Xing Conglian nodded and sighed, raising his chopsticks to put the chicken leg in his own bowl.

Suddenly, the officer continued, “At the same time, another set of DNA samples not belonging to the victim, Tan Kang, was found on the murder weapon, and a match was found in the database with the second set of DNA samples.”

Lin Chen suddenly looked up, and Xing Conglian’s chopsticks stopped in midair.

“Who is it?”

The officer handed over the last piece of paper and said, “His name is Duan Wanshan.”