After transmigrating into the book, I helped my mother reconcile with her divorced husband.

Gu An followed Lu Zhiyuan's words: "The Crown Princess is a divine physician, so does she know why the elixir of immortality cannot make people live forever?"

Seeing Lu Yun looking at him, he scratched his head and said, "I only need an opportunity. What is an opportunity? Don't tell me about Buddhism or Taoism, Your Highness. Although I am a rough man, I know that this opportunity is related to someone."

Lu Zhiyuan said, "It's not related to people, but to snakes."

Although it is unknown what they brought back from Xiawa Village, it must have been examined by the imperial physicians before being consumed. The Imperial Medical Academy did not record it because this matter was related to the emperor's pursuit of immortality, which has always been considered the act of a foolish ruler.

All symptoms appear after the drug is ingested, and these symptoms are always chronic and difficult to detect. Before they are discovered, they may even create some false impressions for the user, such as feeling that they have become stronger.

This is an illusion, an illusion caused by toxins to the body.

When users experience delusions, they may increase the dosage. Once the dosage accumulates to a certain level, all symptoms will become more pronounced.

"General Gu, have you ever heard of cancer?"

"What is cancer?" Gu An shook his head: "I've never heard of it before. Please explain, Your Highness."

“Let me give you an example!” Lu Zhiyuan reached out and warmed her hand on the stove. “There is a very young imperial physician in the Imperial Hospital who pays great attention to his health. He is in very good health and has rarely been sick since he was a child. After entering the Imperial Hospital, he rarely even catches a cold. I saw him at the palace banquet at the beginning of the year and personally took his pulse. His complexion was rosy and his pulse was strong and powerful. No matter how you look at him, he doesn’t look sick or about to get sick.”

"On the third day of the fourth month, his family came to me, saying that he felt unwell but was reluctant to see a doctor and refused to let other imperial physicians examine him. His family had some connection with the Lu family, and upon closer examination, they were distant relatives. At the palace gate, I stopped him and found that he looked listless, his face was yellow, and the color in his lips had faded considerably. He refused my examination, saying that he was fine and had only caught a slight cold. He implied that his family was being nosy and shouldn't have come to my palace for such a trivial matter. Such affection between distant relatives is precious and should not be wasted."

“I don’t agree with his statement,” Gu An said. “The bond between distant relatives is indeed something that can only be used once in a lifetime. According to his plan, it should be used in a life-or-death situation, or at the very least, to benefit himself or his family. But his family hastily used it to treat him to a minor illness that they wouldn’t tell outsiders. In my opinion, however, this is a sign that his family cares about him. He doesn’t think it’s important, but his family does. He should be grateful to his family and touched by their concern for him.”

“That’s right. In the eyes of loved ones, health is more important than future prospects. It’s a pity that he refused my consultation and rejected his family’s good intentions.” Lu Zhiyuan sighed, “He also missed the best time to be treated.”

"A month later, his condition deteriorated rapidly, and even with my superior medical skills, I was helpless. His cancer cells had metastasized to various parts of his body, and he could only watch helplessly as he grew thinner and thinner each day, suffering unbearable pain."

Lu Yun frowned: "What are cancer cells?"

Lu Zhiyuan: "You can think of it as poison."

Lu Yun nodded: "Just like me, all my organs were attacked by toxins. If it weren't for Miss giving me a blood transfusion, I would have been able to watch myself die from the poison."

Lu Zhiyuan patiently explained, "There is a difference! Poisoning has a short onset time, so as long as there is an antidote and a treatment, it will be fine. Cancer has a long incubation period and a short onset time. Once it develops, it is already terminal, and any medical treatment is futile. Even if it can be cured, the process is extremely painful, and there is still a possibility of recurrence after the cure."

Gu An suddenly realized something: "The Emperor's condition after taking the elixir of immortality was just like that young imperial physician the Crown Princess mentioned. Initially, he didn't notice anything amiss, and even a common cold became a problem. The Emperor was greedy, wanting more, so he continued taking the elixir, which backfired. By the time he realized it, his condition was critical and incurable. But I still can't understand how this medicine became poison. The long-lived old man in Xiawa Village is perfectly fine; even without immortality, he's still long-lived. How could the Emperor…"

Gu An's eyes lit up: "I know, that snake. The biggest difference between the old man and the emperor is that the old man was bitten by a snake, while the emperor took medicine on his own."

“General Gu is very clever; he immediately grasped the crux of the problem.” Lu Zhiyuan drew a snake on the paper: “Although we don’t know what the elixir of immortality looks like, the herb that grows in that kind of cave must have some kind of toxicity. The snake lives alongside it and feeds on it when food is scarce. Its toxicity has undergone a subtle change with the snake’s toxicity, and this change is the method of immortality or longevity that His Majesty and Marquis Yongchang have been searching for.”

Gu An said, "The Marquis of Yongchang is so capable, he must have figured out the crux of the problem. But what can he do? Capture the giant snake and send it to the capital? Putting aside whether it would cause a sensation, capturing and transporting the giant snake are problems. Also, what if the medicine has a time limit? For example, what if it works for three days after the giant snake takes it? We can't have the emperor guarding the cave entrance, can we? Even if the emperor is willing, the giant snake might not be?"

Lu Yun added, "Even if the snake were willing, how many bites could it take? The old man's bite was a coincidence, but could the emperor's be? One less bite wouldn't make a difference, and one more bite might kill the emperor. It's a snake, not a spirit pet. Even if it were a spirit pet, it only bit one person by chance. How would it know the severity of its bite?"

“So…” Lu Zhiyuan looked into their eyes: “They are testing, using living people, trying to find out how to live a long life, to achieve immortality.”

Gu An slapped his thigh hard: "Those people in the mountains! I knew it was strange. The mountains were full of signs of human activity, yet we couldn't see a single living person. I asked the villagers nearby, and they said that in previous years, there were often unfamiliar faces in the village. Judging from their clothes, there were soldiers, bandits, and even eunuchs who spoke in a high-pitched voice. The local government issued an order strictly prohibiting villagers from entering the mountains. I thought it was to protect the villagers, but I never imagined it was to protect those people in the mountains, to protect their secrets that cannot be revealed to the public."

"Is the mountain empty?"

“It’s empty, completely empty, not even a ghost can be seen.” Gu An said dejectedly, “It’s my fault, I never thought of this. If I had gone into the mountains earlier, I might have been able to get more evidence. Now, although we have evidence, it’s not enough to point to Marquis Yongchang or the current emperor.”

"General Gu is looking for us because..."

"To clear my name, and that of my brothers," Gu An said. "We did not collude with the enemy, we did not delay the battle, and we did not embezzle military rations. We were wronged, we were murdered to silence us, and our families and descendants should not be implicated by us."