Night of Horror: Finding the True Culprit of the Corpse Gnawing

In a large building of a hospital, there is a very long corridor on the 4th floor. At the end of the corridor is an office and a "morgue" where bodies are kept for autopsy. One night, there was only a very young intern in the office, waiting for an old nurse to take over. Suddenly! She heard a "thud" sound coming from the "morgue" across the hallway. Despite her fear, the young intern couldn't restrain her curiosity and cautiously crept to the door of the morgue. She gently pushed the door open a crack and what she saw was a body that had been gnawed on emitting a green light, accompanied by the "thud" sound she had just heard. The scared intern quickly ran back to the office.

While still shaken, the old nurse arrived. The intern, as if clutching at a lifeline, tremblingly recounted what she had seen in the morgue to the nurse. However, the old nurse dismissed her concerns, saying it was normal. Some patients in the hospital liked to gnaw on dead bodies, and the lights and sounds were made by them, it was nothing to be surprised about. The old nurse also told her that to know who did the gnawing, she just needed to see whose teeth were emitting green light.

So she searched the 1st floor, nothing; searched the 2nd floor, still nothing; searched the 3rd floor, but found nothing. Exhausted, she returned to the office on the 4th floor and told the old nurse that she couldn't find out who did it.

At this moment, the old nurse revealed a smile that was difficult to fathom. She said word by word, "Have you taken a look at my teeth?" Suddenly, she opened her mouth, revealing the old nurse's teeth emitting a terrifying green light, the "thud" sound, and there seemed to be shreds of flesh between her teeth...