One irony in the story is when the policeman brings the Arab prisoner to the schoolhouse and tells Daru that he must take the prisoner to the main police station and turn him over for a trial.  Daru refuses and "Balducci who makes this explicit, promising Daru that once he has delivered the prisoner to Tinguit, ‘‘. . . all will be over. "  Yet, it won't all be over.  It will take Daru on a journey in which he will never be the same.  In someways the act of dealing with this "guest" will change his life forever.

Another irony is that Daru does everything he can to give the Arab a chance to escape, but by being such a good host, the prisoner becomes somhow dependent on Daru.  Sort of like the cat you don't want to have anything to do with, but the more you ignore him the more attention he wants.