Yan Jun was jotting down notes by hand, while a police officer beside him was taking photos with a camera. Leng Ning picked up a surgical knife and made an incision along the midline of the torso, cutting through the skin and subcutaneous tissue, from the neck all the way down to the abdomen. The entire process was incredibly smooth. As blood flowed from the incision, Shu Shu’s legs went weak for a moment.

Di Ye glanced at Shu Shu, “Can you handle it?”

“I can!” Shu Shu forced down the nausea in her heart and said firmly.

The incision, several dozen centimeters long, extended from the neck to the abdomen. Leng Ning, wearing gloves, forcefully pulled apart the skin and muscles, finally exposing the internal organs, which emitted warm white steam under the flashlight. Such a fresh body, still steaming, was extremely rare, and Yan Jun gasped in surprise.

However, Leng Ning was like a cold machine, not even frowning. It made one wonder if he really was a student who had just graduated and started working. Di Ye watched as that bloody hand pulled apart the skin of the deceased’s chest wall. In that moment, the meticulous look in his eyes reminded him of someone he once knew.

Just as his thoughts were drifting, Leng Ning picked up a rib cutter and with a snap, cut through the deceased’s rib, breaking Di Ye’s train of thought. Despite looking frail, he had quite the strength! Leng Ning’s technique was very decisive, each move seemed confident, and this level of skill was impossible to achieve without several years of specialized training. This surprised Di Ye a bit.

“I’m going to lift the deceased’s sternum now.” The officer responsible for taking photos snapped several shots in quick succession.

“The surface of both lungs is smooth, with slight congestion, the heart is of normal size, and there is a bullet hole about one centimeter in diameter in the right ventricle.” He picked up tweezers and extracted a copper-colored bullet from the heart’s damaged area. The bullet clinked as it fell into the tray.

“Now I need to free the entire airway.” After a series of operations, Leng Ning’s bloody hands lifted a section of the freed trachea, with the other end connected to the entire throat and tongue. His bloody hands looked quite horrifying under the light, and everyone around fell silent for a moment.

“The airway is clear, no obstructions.” After a brief thought, Leng Ning added, “Prepare the electric cranial saw.” Yan Jun broke into a sweat at the mention of this. They were about to see the brain!

Sure enough, the next step was to open the skull. The deceased’s hair was already shaved clean, saving Leng Ning a lot of time. He directly made an incision from behind the right ear of the deceased, extending to behind the left ear, then flipped open the scalp to expose the skull. He then picked up the electric cranial saw, slowly sawing open the skull, flipping it open to reveal the brain tissue inside.

The deceased’s brain showed no damage. Leng Ning removed the brain tissue, then cleared the dura mater at the base of the skull, exposing the intact base of the skull. There were no fractures at the base of the skull, and no signs of bleeding on the petrous part of the temporal bone on either side.

Leng Ning pointed at the petrous part of the temporal bone, “Below here corresponds to the inner ear. If the deceased was suffocated, the air pressure in the inner ear would change, causing bleeding in the petrous part of the temporal bone. If it was sudden death, the air pressure in the inner ear wouldn’t change, and this area wouldn’t bleed.”

Yan Jun was surprised, “So, he wasn’t suffocated!”

“Yeah, have the blood gas analysis results and toxicology results come out yet?” Leng Ning asked.

He Le, still a bit dazed by the bloody scene, was momentarily stunned before reacting, “They have!” He showed the report photos received on his phone to Leng Ning.

Leng Ning quickly read through the blood analysis report, “Oxygen partial pressure decreased, carbon dioxide partial pressure increased, arterial blood pH decreased, lactate levels increased… Methamphetamine was detected in the blood.”

Di Ye frowned; he only understood methamphetamine, which is the component of crystal meth. “Speak in layman’s terms.”

“The deceased used drugs before death, but the amount wasn’t enough to cause death. His cause of death is hypoxia.”

Di Ye pondered, “Hypoxia? Not suffocated, so was it respiratory suppression after drug use?”

“Good question,” Leng Ning glanced at Di Ye. Di Ye noticed the slight curve in the eyes behind the protective goggles and was momentarily stunned.

“No underlying disease, normal heart and lung function, no signs of mechanical asphyxia, airway clear, although he used drugs, the dose wasn’t lethal. Why did hypoxia occur? Was it respiratory muscle suppression leading to hypoxia?”

Di Ye: “Are you asking me?”

Leng Ning’s gaze swept over the arc-shaped impression on the deceased’s face, as if talking to himself, “His cause of death is very interesting.”

He placed the surgical knife back in the tray, “If it was hypoxia due to respiratory muscle suppression after drug use, it makes sense. After all, different people have different constitutions… Unfortunately, there’s an impression on his face, which exposes the murderer’s method.”

Di Ye raised an eyebrow; he had noticed the impression earlier but didn’t see anything suspicious.

“What’s wrong with this impression?” Yan Jun leaned in for a closer look, “It looks a bit like an impression left by an N95 mask or something.”

After saying this, he felt it was a bit inexplicable. What does this have to do with death?

“If this impression can’t be explained, the deceased might be ruled as accidental death, which is the cleverness of the murderer.” Leng Ning’s expression quickly returned to indifference, “The murderer prepared for a long time, trying to confuse the public, but unfortunately, in the face of the truth, there’s only one answer.”

At this point, everyone looked at Leng Ning, waiting for his next words.

“There is a very rare method of murder—carbon dioxide poisoning.” Leng Ning’s words plunged everyone present into deep thought.

Shu Shu’s first reaction was: Carbon dioxide can poison someone? She had encountered people who committed suicide by burning charcoal before, but those were carbon monoxide poisoning, carbon dioxide poisoning was unheard of.

Yan Jun was the first to speak, “When respiratory muscles are suppressed, carbon dioxide accumulates in the body. How is this different from what Di Ye said?”

“There’s a big difference. The deceased died from hypoxia in a high concentration of carbon dioxide. As long as the carbon dioxide concentration is high enough, it can be lethal in a few minutes.”

Di Ye’s fingers half-curled, rubbing his stubble, “So you think the murderer used high concentration carbon dioxide to kill?”

“When the human body is exposed to high concentrations of carbon dioxide, it experiences hypoxia in a short time. The poisoned person’s breathing deepens and quickens, and the body undergoes a series of hypoxic reactions, including dizziness, nausea, vomiting, palpitations, tinnitus, and eventually cardiac arrest.”

Yan Jun: “According to you, if the carbon dioxide concentration in the room was so high, why was the waiter who entered fine? The room is so large, reaching a lethal concentration would require a lot of carbon dioxide. Filling it with gas would take a long time, where would they get so much carbon dioxide?”

“No need for such trouble,” Leng Ning said. “All that’s needed is a pressurized carbon dioxide cylinder and a breathing mask.”

Di Ye suddenly realized, “So that impression was left by a breathing mask?!”

“The murderer could think of such a method to kill, clearly premeditated. To make it portable, this thing wouldn’t be too big. Pressurization can store gas, and the container might be something like an oxygen tank.”

Leng Ning quickly sketched a gas cylinder connected to a mask on paper. Di Ye took the drawing and immediately understood what the other had drawn, “He Le, take some people to the scene to find this gas cylinder, don’t miss any corners! Recheck everyone who entered the room, reconstruct each person’s action trajectory.”

“Got it, boss!” He Le immediately took a group of people out of the interrogation room.

Di Ye suddenly looked puzzled, “I have a question.” He pointed at the copper-colored bullet in the tray, “Since he died from carbon dioxide poisoning, why was there a need to shoot him?”

“If I were the murderer, I wouldn’t bother,” Leng Ning said while packing up his tools, “If it weren’t for the impression revealing the murder method, this plan was almost perfect, no need for an extra shot.”

Di Ye looked at Leng Ning, frowning in thought. Leng Ning was right; the murderer had no need for an extra shot, so someone else must have fired it. Who would choose to shoot after the person was already dead?

Half an hour later, Di Ye’s phone rang; it was He Le calling, “Boss, we found a gas cylinder and mask in the stairwell storage room, just like he said!”

“This guy is amazing…” Yan Jun clicked his tongue, “If we hadn’t found the evidence, I wouldn’t have believed his deduction. Do you call this talent?”

“This is more than just talent,” Di Ye looked at Leng Ning’s back, “Did you see the calluses on his index finger and thumb? That’s from holding a surgical knife for a long time. This guy is not simple.”

He Le hung up the phone, unscrewed the pressure valve on the oxygen cylinder, and immediately gas started to spray out of the cylinder. He leaned in to smell it, no scent. But his intuition told him this gas wasn’t oxygen. He quickly took the cylinder back to the lab.

However, sending the cylinder to the lab encountered a problem. “It’s already past 2 AM, the earliest results won’t be out until tomorrow morning.”

“Call someone to get up and test it.”

Just as Di Ye picked up his phone to make a call, he heard Leng Ning’s indifferent voice from behind. “Mind if I borrow the lab for a bit?”

*

In the cold laboratory filled with various bottles and instruments, Leng Ning sat at the table, meticulously focused on the reagent in front of him. Di Ye stood beside him, watching him fiddle with incomprehensible bottles and liquids.

“Didn’t expect you to be quite responsible,” Di Ye suddenly remarked.

“You’re overthinking it. I just want to know the results sooner.”

Di Ye clicked his tongue, crossing his arms and leaning his butt against the table edge, his long legs crossed, “Is this humility?”

Leng Ning didn’t answer him.

The wait for the results was a bit boring, and Di Ye paced around the lab, occasionally glancing at Leng Ning and those experimental instruments. Leng Ning didn’t seem to be in a hurry; he always appeared calm and organized when doing things.

Di Ye noticed this person seemed to have another trait: whatever you asked him, his answers were always polite, and for questions he didn’t want to answer, he simply stayed silent. No matter how anxious you were, it was useless.

Ten minutes later, the results were out. “The reagent changed color, there’s a high concentration of carbon dioxide in this cylinder.”

Yan Jun extended a friendly hand to Leng Ning, “I apologize for earlier, hope we can continue to cooperate in the future!”

“Different fields have different expertise; what you understand, I may not,” Leng Ning didn’t extend his hand but handed the signed autopsy report to Yan Jun’s outstretched hand, “Glad I could help.”

Yan Jun was stunned for a while. He wasn’t reaching for the report; he wanted to shake hands!

“Hehe… right, right…” Yan Jun’s expression was awkwardly stiff.

Leng Ning: “If there’s nothing else, I’ll be going.”

“I’ll see you out.” Di Ye, holding a cigarette, stood by the window smoking, “The car’s just downstairs.”

Leng Ning turned to look at him, “No need, I’ll catch a cab.”

Di Ye stubbed out the cigarette and walked over to Leng Ning. He directly pulled out his wallet, casually took out some bills, and stuffed them into Leng Ning’s hand, “Find a place to eat something first. There’s a hotel near Longchuan River. After eating, find a hotel to rest before going to the scene. If Old Zheng rushes you, just say I said so.”

A barely noticeable smile tugged at the corner of Leng Ning’s mouth, “No need, I’ll rest in the car for a while, but thanks for the kind thought.”

He folded the money and gently tucked it back into the pocket on Di Ye’s chest, “So Captain Di has a habit of giving tips.”

Di Ye: “Eh? No, I was just…”

“Ding—elevator’s here.”

Leng Ning turned and entered the elevator, not caring what the other wanted to say. Seeing Di Ye still standing at the elevator door, he raised a hand to hold the elevator door for him, “Are you coming down?”

Di Ye put the wallet back in his pocket, thinking: What am I explaining to him?

Leng Ning: “?”

“Never mind, I’ll see you down first.”