Yang Ping nodded and didn’t ask further. He took another walk around the laboratory, glanced at the literature on the bookshelf, checked the experiment log, and finally stopped at the door.

"Has Professor Zhou shown any unusual signs in the last six months?" he asked Li Xiong, "Physically, or behaviorally?"

Li Xiong thought for a moment and said, "Physically... he has lost some weight recently, but it’s normal for older people to get thinner. Behaviorally... he seems more silent than before. He used to chat with us when he came to the lab, but he hasn’t spoken much in the past six months, just buries himself in experiments."

He paused, suddenly recalling something: "Oh, about two months ago, he asked me a very strange question."

Yang Ping’s gaze sharpened: "What question?"

Li Xiong said, "He asked me if an organophosphate compound could be absorbed by a person without inhalation through the respiratory tract or ingestion via the digestive tract. I said, theoretically, it could be absorbed through skin contact, but the absorption efficiency is very low. After hearing this, he nodded and said nothing more."

Yang Ping’s expression remained unchanged, but Dr. Yuan noticed his fingers twitch slightly.

"Thank you," Yang Ping said. "Let’s leave it here for today."

As they walked out of the laboratory building, the sky had turned completely dark. Dr. Yuan asked, "Professor Yang, what do you think?"

Yang Ping was silent for a long time, then said, "I need to think more about this. Let’s discuss it tomorrow. I’ll have an answer for you then."

On the way back, the car was very quiet. Zhaxi sat in the back seat, his mind in turmoil. Organophosphate compound, skin absorption, constricted pupils, pigmentation, books on the shelf, mysterious reagent bottles in the lab; these fragments swirled around his mind, but he couldn’t piece them together.

He glanced at Yang Ping, who sat with his eyes closed, leaning against the seat, motionless. 𝘧𝓇ℯ𝑒𝓌𝑒𝑏𝓃𝘰𝘷𝘦𝘭.𝒸ℴ𝓂

Zhaxi knew he wasn’t asleep; he was thinking, pondering the connections between those fragments.

The car arrived at the entrance of Sanbo Hospital, and Yang Ping opened his eyes and got out of the car. Zhaxi followed him into the hospital.

When they reached the building of the Institute, Yang Ping suddenly stopped.

"Zhaxi, what did you see today?"

Zhaxi thought for a moment and said, "A suspicious death, constricted pupils, pigmentation, chemical smell in the house, books on the shelf, reagent bottles in the lab."

Yang Ping nodded: "Do you think there’s a connection between these things?"

Zhaxi hesitated for a moment: "Yes, but I don’t know what the connection is."

Yang Ping said, "Then investigate. Look into all the clinical symptoms of organophosphate poisoning, the cases of skin absorption of organophosphate, and whether there’s any relation between organophosphate compounds and pigmentation. Tomorrow morning, come back and tell me your thoughts. An excellent doctor’s deductive ability is no worse than a detective’s. Diagnosing complex cases involves connecting the dots between fragmented symptoms, signs, and examination results."

Zhaxi took a deep breath: "Okay."

That night, Zhaxi researched all the information on organophosphate poisoning and listed the clinical symptoms: constricted pupils, salivation, sweating, muscle tremors, pulmonary edema, respiratory difficulty, consciousness disorders. But the deceased only had constricted pupils with no other symptoms.

He also looked into cases of skin absorption of organophosphates. Indeed, there were cases, but they usually required a long time or high concentrations, and the symptoms of poisoning from skin absorption are less typical, often with only mild systemic or local manifestations.

Then he researched the relationship between organophosphates and pigmentation. After a long search, he found an old paper mentioning a rare disease called "organophosphate-induced melanosis." Long-term contact with organophosphate compounds could cause grayish-brown pigmentation on exposed areas like fingertips and face.

Zhaxi stared at the screen, his heartbeat accelerating.

He connected all the clues: long-term exposure to organophosphates, skin absorption leading to chronic poisoning, causing pigmentation and weight loss. Then, at a certain point, a larger dose exposure led to acute poisoning, severe pupil constriction, respiratory suppression, and death.

But how did this "larger dose exposure" occur? Was it the cup of tea? The book? Or something else?

He remembered what Yang Ping said: "The books on his shelf are too well-preserved."

What if those books weren’t meant for reading? What if they were meant for something else?

A thought suddenly flashed through Zhaxi’s mind, but it was too significant for him to dwell on.

He checked the time; it was already past eleven. Yang Ping’s words came to mind—"Sleep before eleven every day; that’s an order." He hesitated for a moment, then closed the computer.