When they came out of the vent, they found themselves in an abandoned garden, overgrown with weeds and some ancient sculptures scattered on the ground.

"We finally got out!" Xiao Wang said happily.

Li Yu looked around and said thoughtfully: "This should be the back of the hospital. Let's go in through the back door of the hospital and continue our investigation."

They walked into the back door of the hospital and found that it had been turned into a nursing home. The elderly people in the nursing home looked very kind, but they always felt that there was something hidden here.

They began to look for clues in the nursing home, when suddenly an old man came over. The old man looked very weak, but there was a hint of cunning in his eyes.

"Are you here to investigate that secret?" asked the old man.

Li Yu nodded and asked, "Do you know that secret?"

The old man sighed and said, "I know the secret, but I can't tell you. The secret is too dangerous. You can't reveal it."

"Why can't it be uncovered? Will it cause a greater disaster?" Li Yu asked.

The old man hesitated for a moment and said, "Uncovering that secret will put us all in danger. You should leave here and don't pursue it any further."

Li Yu felt that the old man must know something, but he was unwilling to reveal it. They had no choice but to leave the nursing home and continue looking for other clues.

During their subsequent investigation, they discovered some historical information about the hospital. It turned out that the hospital had once been a psychiatric hospital, specializing in the treatment of mental patients. However, a sudden fire destroyed most of the hospital building. After the fire, the hospital was closed and became known as a haunted house.

They also discovered some rumors about the fire. According to the rumors, the fire was caused by a fight within the hospital over experimental results. Many people died in the fight, and the hospital director also disappeared in the fire.

Li Yu thought that this rumor might be the secret they were looking for, so they decided to investigate the truth of the fire and uncover the secret of the hospital.

During their subsequent investigation, they discovered an important clue: the hospital director was conducting an experiment on mental illness. The purpose of this experiment was to study the thinking patterns of mentally ill patients in order to find the best way to treat them.

However, this experiment caused dissatisfaction within the hospital. Some doctors and nurses believed that