The setting is very symbolic to the ideas of free will and consequences. First of all, the action takes place inside a school house, a place of learning. Daru, in particular, is facing a learning experience in his life - can he assimilate his beliefs with the demands that are being made of him at the moment? He has sympathy for the Arabs, but he must ally with the Algerians in a state of war. However, a state of war has happened, leaving him to feel that he shouldn't be aiding any Algerian action. However, he has been ordered to. Also, he can't find a way to justify the murder the Arab committed. So, Daru must learn what to do in such a morally ambiguous situation. Hence, the school house.
The unseasonable storm that sets up the story is also symbolic. It is a warning of the danger that is to come. Daru struggles, then makes a decision to help the Arab. The consequence is that he receives a death threat from the Arab's compatriots. The unsettled nature of the storm symbolizes Daru's unsettled feelings as he struggles with his free will, and the negativity of the storm symbolizes the consequences.