What is the atmosphere in "After Twenty Years?"

In the short story "After Twenty Years," the author O. Henry creates an atmosphere of mystery and uncertainty to set up the surprise ending. He does this by describing the weather, the time, and the lack of pedestrians.


The time was barely 10 o'clock at night, but chilly gusts of wind with a taste of rain in them had well nigh depeopled the streets.



The vicinity was one that kept early hours. Now and then you might see the lights of a cigar store or of an all-night lunch counter; but the majority of the doors belonged to business places that had long since been closed.


From these descriptions, the reader is immersed in a setting of a street that is dark, windy, and almost deserted. This creates the atmosphere of mystery that the author is trying to convey. When the policeman sees the lone man standing in the doorway of a shop, the atmosphere of mystery is heightened, for the reader becomes curious about who this solitary person in such a bleak setting could be. To add to the atmosphere, the description of the stranger in the doorway is framed by the lighting of a match, so that the policeman catches only a glimpse of the man's face. The author adds further to the mystery by explaining that the man has a slight scar on his face and a scarfpin and watch that suggest that he is very rich. It's impressive that with a few well-placed words and phrases, O. Henry is able to create such a mysterious and atmospheric setting for this fascinating and surprising story.

The atmosphere of "After Twenty Years" establishes the mood of mystery and suspense that sets up the story's surprise ending. It is night as the story opens. The cop is on patrol and the weather is pretty unpleasant. It's cold, the wind is blowing, and the gales are flecked with a little rain. The part of the city where the cop is walking is mainly shrouded in darkness. Most of the properties in the area belong to businesses that have long since closed for the day. As such, there aren't too many people around, except for the occasional patron of a small restaurant.
All of the various ambient elements provide the perfect setting for the story. The darkness and relative isolation of the location allow us to concentrate more easily on the two characters and their fateful meeting. And by setting the story at night and in inclement weather, Henry is cleverly hinting that the meeting won't have a very happy ending for at least one of the two men.