Daru is French, a former schoolmaster living in near El Ameur, Africa. He still teaches in his little home to the native Africans. He has left the chaos of Europe for the relative solitude of Africa: "...he lived almost like a monk in his remote schoolhouse, nonetheless satisfied with the little he had and with the rough life, had felt like a lord...".
Balducci is the gendarme who brings the Arab prisoner to Daru. He insists that Daru transport the prisoner the rest of the way to the jail. Daru tries to protest that it is "not his job" but Balducci tells him that in wartime, he must, as a French citizen, do what he is told.
The Arab is Balducci's (and Daru's) prisoner. He is accused of having murdered his cousin and thus "stirring up" trouble in his village. He is taken by Balducci to Daru, who is ordered to take the Arab to the prison in Tinguit.
Balducci is a flat character. He come briefly in, does his job (propels the plot forward) and leaves. The only truly round character is Daru, who must struggle with his conscience and knowledge of the people of Africa and his own European identity.
As for the Arab, we never learn too much about him. He is silent most of the time, except for a few simple questions. Camus' story is more about Daru than anyone else and his confused feelings about his role in the prisoner's life, in Africa, and as a European.