The informant grew up in Beijing. We were discussing ghost stories when she brought out this story.
A man bought a new apartment. It was on the first floor. Outside the window is the garden, a small grassland in a residential district. He said that when the apartment was being furnished, he often saw an old man staring at him strangely from the window. When he walked outdoors to find the old man, the old man disappeared. When he moved into the house, a friend of his came to visit him. He told his friend that he often saw an old man. He asked his friend to go out and take a look, while he stood indoors to see whether the old man disappeared from the window. The friend went out, and then ran in hurriedly, brought him out and said, “You could not live in the apartment. The old man is a reflection on the window.”
Because the old man is a reflection on the window, he is a ghost in the house. The main motif of the story is that mirrors or mirror-like object (window in this story) can show the reflection of ghosts, even though ghosts cannot be seen directly. Notice that the ghost is an old man. The old man must have some unfulfilled wishes that connect with the apartment – he probably lives in the apartment. To me, the story reflects the anxiety of the working force who fail to pay enough attention to their aging parents.