Zhaxi was stunned: "Then what about the threat letter? Saying ’Thirty years ago, do you think no one knows it’?"

Yang Ping shook his head: "That’s the issue. If someone is threatening him with this matter, what kind of ’truth’ does the threatener know? Is it that Zhou Huaixin concealed the toxicity data? Or did Zhou Huaixin do the right thing but was misunderstood?"

Zhaxi opened his mouth but couldn’t answer.

Yang Ping closed the folder and placed it on the table. He said, "Zhaxi, you know, in clinical cases, the hardest to diagnose are not those typical ones, but those that other doctors have misdiagnosed. Because a misdiagnosis will leave a preconceived impression that leads you to gather evidence in the wrong direction."

He paused, then turned to look at Zhaxi: "This case is the same. We now have two possible explanations, murder and accident. But if we have already decided on one in our hearts, we will subconsciously look for evidence that supports it, ignoring evidence that negates it. This is the mistake clinical doctors easily make, and also the mistake those solving cases easily make."

Zhaxi nodded. He understood Yang Ping’s meaning, to not pre-set positions, let the evidence speak.

Yang Ping stood up and returned the folder to Teacher Sun: "We need to make a copy of these materials, is that okay?"

Teacher Sun nodded: "Sure, I’ll help you with the copying."

After the materials were copied, Yang Ping and Zhaxi walked out of the archives. Zhaxi followed behind Professor Yang, feeling heavy in his heart.

When they returned to the hospital, it was already 7 PM. Zhaxi returned to his dorm, spread out the materials photocopied today on the bed, and read them one by one. He scrutinized every number and every sentence, wanting to find more clues about A-8, about Professor Zhou, about that project from thirty years ago.

He saw the last page of the internal report, which was a list of the project group’s members. There were six people on the list, with Zhou Huaixin being the third. The two listed before him were a researcher from the Ministry of Chemical Industry Institute of Pesticide, surname Liu, and another was a retired professor from the Department of Chemistry at Nandu University, surname Fang. The three people listed after Zhou Huaixin were all ordinary members of the project group.

Zhaxi stared at this list for a long time. He suddenly thought of a question, what exactly was the "thirty years ago event" mentioned in the threat letter? Did Zhou Huaixin hide the toxicity data? Or was it something else?

In fact, Officer Yu is also contemplating these issues, just that Zhaxi’s focus and thought process are different.

He picked up his phone and sent a message to Yang Ping: "Professor Yang, are the two people listed before Professor Zhou in the project group still alive?"

A few minutes later, Yang Ping replied: "Checked, Researcher Liu passed away in 2010. Professor Fang is still alive, residing in Nandu, eighty-one years old this year. Officer Yu will visit him tomorrow."

Zhaxi breathed a sigh of relief, at least there was still someone to ask.

He started reviewing other materials again. When he reached a 1992 meeting minutes, he suddenly stopped. The minutes were for an evaluation meeting regarding the A-8 project, documenting the speeches of various experts. Zhaxi flipped through page by page and reached a segment on the third page:

"Researcher Liu from the Ministry of Chemical Industry Institute of Pesticide: The insecticidal activity of A-8 is indeed very high, but the toxicity data needs further verification. According to our repeated experiment results, the percutaneous toxicity of A-8 is about 30% higher than the data reported by Professor Zhou. It is recommended to postpone further development of this compound until the toxicity data is confirmed."

Zhaxi’s head buzzed. The percutaneous toxicity being 30% higher than Professor Zhou’s reported data? What does this mean? Professor Zhou’s data is 2.5mg/kg, if 30% higher, that would be about 1.9mg/kg. But that’s not the point— the key is, Researcher Liu said "needs further verification," does this mean Professor Zhou’s data might have issues?

He continued to read on, and next was Professor Zhou’s response:

"Professor Zhou Huaixin: Our experiments were strictly conducted according to standard operating procedures, and the data is reliable. Differences between data from different laboratories are normal, possibly related to animal strains, experimental conditions, and other factors. It is recommended to undergo redundant verification by a third-party laboratory."

Then there were no more records, Zhaxi turned to the last page. The conclusion of the meeting was: "In view of the controversy over A-8’s toxicity data, it is recommended to suspend the industrialization process of the project until the third-party laboratory completes the redundant verification and then make a decision."

After reading it, Zhaxi took a photo of these minutes with his phone and sent it to Yang Ping. Then he sat on his bed, his mind in a jumble.

What if Professor Zhou’s data really has problems? What if he underestimated the toxicity of A-8, allowing the project to get approved, only to be stopped when discovered later? Could the "thirty years ago" mentioned in the threat letter be about this?

But Yang Ping was right, do not presuppose positions, let the evidence speak.

He looked at the clock, it was almost 9 PM. He stood up, intending to go to the canteen for a late-night snack. As he reached the door, his phone rang. It was a message from Yang Ping: "Saw the meeting minutes you sent, interesting. Tomorrow morning, join Officer Yu to meet with Professor Fang."

Zhaxi replied with a "Okay," then headed to the canteen.

There weren’t many people in the canteen. Zhaxi got a meal and found a corner to sit down. While eating, his mind was filled with the words on those files—A-8, LD50, percutaneous toxicity, data dispute, threat letter, remnants on the page.