The two went to the Meteorology Bureau. The experts had worked out a mathematical model to estimate the starting point of the balloon. After they had calculated, Chen Shi was given a rough range. Chen Shi picked up the map and said, "This is too large. It’s almost an entire district."

The experts said, "We can’t help it. The air flow at high altitudes is unpredictable. It’s impossible to accurately infer the coordinates, and the fact that so many balloons fell at different locations in the city means that they weren’t released at the same time. Between the first and last balloon, the interval could have been a whole night, or it might have just been within an hour. We calculated with the inclusion of all the margins of errors and we got such a large range."

"Were the winds chaotic that morning?"

"Very."

"If you were a murderer, what strategy would you use to fly the balloon in order to prevent being traced back?"

The experts waved their hands and said, "We dare not imagine this!"

"Let’s discuss it!"

Thus everyone discussed it. At first, everyone was a bit hesitant, but with time they began to let down their guards. Some people said that the balloons would leak, so you could apply a layer of glue to delay the deflation. Some also said that you could put some dry ice in the bag. After the dry ice had melted, the balloon would rise and fly even further.

Listening to the discussions of these experts, Lin Dongxue asked skeptically, "Would the killer be so smart?"

"I always tend to think of murderers as being extremely intelligent. When a person is eager to evade responsibilities for their crimes, they will display more ingenuity than usual. This is called adrenaline-fueled cognition."

"But there are also murderers who make more mistakes the more they panic.”

Chen Shi smiled. "Those murderers will usually be dealt with by the police and the cases won’t come to me. You guys only look for me when the case is difficult."

"That makes sense."

Chen Shi called Peng Sijue and asked him to double-check what was on the balloons and bags. He also took a photo of the experts’ draft calculations.

Then Chen Shi and Lin Dongxue drove the car to the gymnasium where the balloons were stolen, and parked the car outside. Lin Dongxue asked curiously, "Why are we here? The local police have taken over the investigation regarding the balloon theft, so we don’t need to intervene.”

At that moment, several police cars were parked outside. Chen Shi looked at his phone and said, "I'll calculate the distance. Let’s get out."

The two got out of the car and walked to the warehouse. They stopped for a while before returning. It took a total of twenty minutes for them to return back to the car. Then Chen Shi drove towards the investigation area. Two hours later, he reached the area that the experts had designated.

He continued to drive onwards for another four hours. Chen Shi stopped at the side of the road, took out the map and said, "Four hours is the limit. Dawn is around 5 o’clock at this time of the year. If the murderer hadn’t gotten the balloons by four in the morning, the murderer’s corpse abandoning plan would have to be delayed by a day."

"But there’s not a lot of people on the streets early in the morning."

"The killer won't release the balloons after dawn. It’s a corpse! It wouldn’t be good even if they were seen by someone sweeping the streets!” Chen Shi drew a large circle on the map, which was the radius of the car departing from the gymnasium to where they were just then.

"My brother is also investigating the footage at the traffic management bureau."

"That's even better. We’ll take a two-pronged approach."

At that moment, Peng Sijue sent several WeChat messages. He said in WeChat, "The composition of substances on the surfaces of the balloons is complex. Maybe air pollutants had become attached to them in the sky, but a small hole was found at the bottom of each balloon. It’s suspected that the killer had injected some water in the balloons. The water leaked out slowly during their flights. The ultimate loading weight of this type of balloon is ten kilograms. Even if there were three kilograms of water in them during take-off, I applied the formula you had photographed and finally got this approximate range. The middle section of Hengyang Road is the center with a radius of ten kilometers going outwards.”

Chen Shi replied, "Thank you!"

The range was reduced by half again. Chen Shi glanced at the circled map. His finger was at the intersection of the two circles, and said, "Let's start checking from here!"

After a day of driving, it was already afternoon. The two of them bought fast food to assuage their hunger. After arriving at the area, Lin Dongxue asked, "Didn’t we come here yesterday?"

"Yes, one of the supermarkets that sells folding saws is over there..." Chen Shi's eyes fell on a tall building not far away. "Dynasty Hotel. Were the balloons really released there?"

"Let’s go and see!"

The two stopped in the hotel parking lot and went to the hotel’s entrance. They saw a group of young people holding signs with the words "Luo Zuyu, I love you" and the like. At that moment, three black cars stopped in front of the hotel. A well-dressed young man got out, accompanied by bodyguards and his manager. The fans immediately rushed over, cheering while the bodyguards desperately pushed them away so as to maintain order at the scene.

"Add oil, Luo Zuyu! We believe in you!" Some of the fans shouted cheers, and the others followed suit. Luo Zuyu nodded, greeted everyone and walked into the hotel.

"Wow, it's really him!" Lin Dongxue said, "He looks very different from his image on TV. He looks sickly."

Chen Shi was silent, staring at Luo Zuyu's rear view deep in thought.

When the two went inside the hotel, Lin Dongxue presented her credentials and asked to see the check-in records for the past few days. However, the hotel staff said, "Sorry, our hotel keeps the customers' information strictly confidential and cannot disclose it publicly."

Chen Shi thought to himself that it seems that the people who stayed here were either rich or powerful. Lin Dongxue questioned, "Can the police not access it either?"

"Only if you have a search warrant from a prosecutor."

"Can we watch the surveillance videos then?"

"No!"

Lin Dongxue was annoyed and was about to call Lin Qiupu. Chen Shi stopped her and said to the staff at the counter. "Book a room for me. I want one on the highest floor."

"The rooms above the 20th floor are all VIP suites. Are you sure?"

"Yes!"

"How about the 22nd floor? It’s all full up above that floor."

Lin Dongxue pulled Chen Shi's arm and whispered, "Don't spend this money pointlessly."

"It's all right."

Chen Shi paid the deposit. The VIP room cost 5,000 yuan a day. It was really painful, but he had to bear it for investigation purposes.

The staff member escorted the two to the room and they reached the 22nd floor. Chen Shi said, "We’re not in a rush to enter the room. I’ll have a look at the structural layout of the entire floor."

The staff member smiled in contempt. She was used to seeing skinny people punch themselves until their faces swelled up so they could pretend to be fat[1]. He was just like Granny Liu visiting the Grand View gardens[2]. As soon as he had come in, he looked around at the entire place like a fool.

Chen Shi walked up and down the corridor. The corridor was covered with thick carpets and some oil paintings were hung on the walls. There were surveillance cameras at both ends. The noise reduction effect was very good and they couldn’t even hear a hint of what was going on in the rooms. He reached out to touch an oil painting on the wall, and the staff reminded him, "Sir, you can’t touch it."

Chen Shi pointed at the surveillance camera. "How’s the security here?"

"Foolproof. The security room has three groups on roster that take shifts to be on duty every day. If someone wants to come in, the consent of the room owner must be obtained before they’ll allow them to come up from downstairs."

Chen Shi nodded. At that moment, they heard a commotion. The three walked over and saw a fat man in red pajamas holding a vase. He was arguing with a staff member, "How do you do cleaning around here? I spent tens of thousands to stay in this presidential suite. Do you treat your customers like this? Look at this vase. Who vomited into it? It’s sickening! Go and find your manager for me!"

1. It’s an expression that describes people who desperately act like something they’re not. In this case, she means to say that Chen Shi is a poor person who is trying to act rich. Fat people used to be associated with wealth because they were clearly the only people who could afford food.

2. It’s a reference to the novel Dream of the Red Chambers. It’s used to describe people who act like country bumpkins.