Tang: Zhang San went to the toilet and found that he could not go out.
Clue: Zhang San's four inner monologues
... Seems to be able to go out again?
... Can I really go out?
... No way! Never go out!
... I thought, I should not be able to go out...
bottom:
Zhang San found that someone outside the toilet was killing people, and the timid Zhang San did not dare to stop it, so he could not go out. After the killer seemed to leave, he said he could go out again. As a result, the murderer actually went to get the tools and came back to divide the body into sacks, so he couldn't get out again. At this time, the corpse became a ghost with resentment, and the murderer came to kill Zhang San in the toilet, because Zhang San did not stop the murderer when he killed people.