Lin Qiupu decided to leave first and left it to them. Chen Shi stared at the victim's seat and thought without a word. Lin Dongxue urged, “Help me check the luggage!”

“You check it first. I want to check some areas around here.”

Chen Shi opened the curtain and entered the flight attendant's resting lounge. Lin Dongxue and other police officers began taking out the luggage under the seats one by one to investigate them. After checking each one, they made a circle on the passenger list.

When opening one particular leather suitcase, Lin Dongxue felt that there was something on the outer wall of the case. She called on the others to come and see, but there was no sharp object at hand. While she was worrying, Xu Xiaodong ran in and said, “Brother Chen! Where’s Brother Chen?”

Lin Dongxue stood up and suddenly felt dizzy. It took awhile for her to feel better. She asked, “Did you finish that experiment?”

“It's done! The test proves that the airport inspection is also flawed. Voila!” Xu Xiaodong took off his shoes and took out a pair of collapsible scissors from under the insole. “When I passed the security check, they didn't find anything hidden in my shoes.”

“Just right. Let me use the scissors.” After taking the scissors, Lin Dongxue frowned. “What's this smell?”

Xu Xiaodong bowed his head and smiled. “What do you think? It was hidden in shoes.”

Lin Dongxue cut the suspicious leather suitcase with scissors and found some pills in between the leather. Xu Xiaodong exclaimed, “Drugs! What an unexpected discovery.”

Lin Dongxue marked the name of the baggage owner and put a question mark next to their name. The pills needed to be taken for testing later.

Chen Shi opened the curtain and said, “Did you finish the investigation?”

“It's only half done!” Lin Dongxue looked at the long aisle ahead.

“I don't think the murder weapon will be found in the luggage. The murderer isn’t that stupid. Check the seats and garbage bags.” Chen Shi picked up a garbage bag and found the wrapping paper for food and a crumpled piece of foil.

Suddenly, he said, “I'm going to find Old Peng. You guys continue busying yourselves!”

“Hey, hey! Why don't you help?!” Lin Dongxue shouted after him, but he had already left.

Xu Xiaodong sighed. “That's what Brother Chen’s like. As soon as he thinks of something, he needs to go and do it. But he’s always so accurate.”

“Don't stand around. Come check the luggage together with us.”

In addition to this suitcase, they also found some cutlery with knives in another person’s luggage. This discovery surprised everyone, but when Lin Dongxue picked it up, they found that it didn't feel right. It turned out to be a rubber knife. No lethality at all.

However, just in case, she marked down the owner.

After checking all the luggage, it was eleven o'clock. Lin Dongxue almost couldn’t handle how tired she was. At this time, Chen Shi and Peng Sijue got onto the plane, and Peng Sijue held a testing kit in his hand. Chen Shi smiled and asked, “Did you finish with the investigation?”

“You make it seem like it’s easy but you didn’t even help!” Lin Dongxue complained.

“Sorry. I thought of something, so I called Old Peng over to help.”

“Oh yes, Captain Peng. Here are some pills for you to test. There were a few suspicious pieces of luggage. I’ll go and question their owners.”

Chen Shi took the pills and asked, “Was it found in the luggage?”

“Yes.”

“Leave this alone. There are less than four hours left. If the case is investigated so thoroughly, we won’t be able to find anything even the day after tomorrow… You should go see the flight attendants and ask them which passengers used the toilet after take-off. All the passengers who passed by the victim’s seat need to be recorded.”

“Oh and pay attention to whoever is wearing a dark blue khaki coat. Especially if there’s a slight tear on the clothes, particularly around the sleeves.” Peng Sijue added.

Lin Dongxue nodded. “I'll go now!”

After the other police officers left, Chen Shi said to Peng Sijue, “Let's go!”

Peng Sijue picked up the reagents and held the ultraviolet light up. He began the test from the toilet to the aisle while Chen Shi was inspecting the kitchen on the plane. In reality, it was just a place where food could be heated up.

“Old Peng!”

Peng Sijue looked back and reached out to catch something that Chen Shi had thrown over. It was something wrapped in foil and it was still warm.

“This is…”

Chen Shi also had one in his hand and said, “Airplane food. It’s a hamburger. I just heated it so we can use it to feed our hunger for now!”

“Can you stop making crime scenes your home?”

“If you won’t eat it, I will.”

Chen Shi opened it and took a bite. It was the most unpleasant burger he'd ever eaten in his life. It was a big piece of bread with ham, sausage slices and vegetable leaves sandwiched in between. It had no taste at all.

He took out the burger and put it on a seat. Then, he flattened the tin foil and carefully folded it into a flat awl. He used it to try to pierce the bread. The knife folded by the tin foil could easily pierce the bread.

Chen Shi used the foil knife to poke his finger. Although it was very pointy, it wasn’t strong enough to pierce his finger.

So, he improved it by folding the foil knife even more, making it tighter and sharper. He was actually able to pierce his finger this time and looked at the blood on his finger. He seemed to have an epiphany.

“Old Chen!”

Chen Shi quickly sucked the blood from his fingers and ran over. He saw the ultraviolet light in Peng Sijue's hand illuminating a bloody spot on the floor. There wasn’t much blood and it looked like it was wiped clean with someone’s feet.

Chen Shi looked back. “It's two rows away from the seat of the victim.”

“I also found it in the back. There are three places with blood at an average of ten centimeters apart.” Peng Sijue continued moving forward, but there were no more stains after. There were only these three blood spots.

Chen Shi speculated, “This is the blood that dripped from the weapon. Have you tested the composition of the victim’s wound?”

“No, the results aren’t out yet, but the drug was determined to be a tranquilizer. The deceased should have taken it before his death. He was in a state of neuro-suppression, so when he was killed, he hardly struggled.”

“Is there blood in the toilet?”

“No.”

“What about the toilet over there?”

“Let’s go and see.”

The two got to the washroom on the other side and Peng Sijue sprayed some Luminol reagent on the ground and in the toilet. He used the ultraviolet lamp and found nothing around the toilet. Then, he checked the wash basin again. Unexpectedly, there was a trace of blood on the sink.

“This blood stain was left behind recently. It’s probably the victim’s blood. The killer must have washed their hands here.”

“They killed someone and then came all the way here to wash their hands. I’d do the same. Once the victim is found, everyone’s attention will be on the front row. Nobody would pay attention to the back rows.”

“Would the murder weapon also be here?” Peng Sijue pointed to the toilet.

“I heard that the excrement on a plane will be thrown into the air and frozen into a blue popsicle as it goes down. Is that true?”

“Some aircrafts that have strict weight limits will do this, but this type of passenger aircraft will not. The excrement will be stored and returned to the ground to be dealt with by ground staff.”

“Does this count as common knowledge?”

“What?”

“I mean, would the murderer know about this and give up his intention to deal with the weapon through the toilet?”

“How would I know?!”