Roses Are Red
The main location is in a big city in Virginia somewhere. I know this because it stated that it was in Virginia, but I inference it is in a big city because Alex, the detective, is investigating multiple bank robberies in a twenty mile radius. He is always at a different bank every time too. This proves that the city has multiple banks which concludes that it is large. It is also probably late spring or summer months during modern day because it states how multiple people are out walking on the streets and how Alex was sweating when he chased after a possible suspect.
If the setting were to change, the plot would be effected as well. If it were in the winter months, it would definitely be a lot more difficult for the criminals and the police as well. The weather would be an obstacle that they would have to deal with. Also, if the time period were changed, the criminals would not be accomplishing the task the same way. They would have different motives and different ways of doing it because through the years every day life changes.