The thief is more about the boy than anything else. The father wants to punish the thief for stealing their cart. The boy refuses to let his father harm the thief when they catch up to him. He even convinces his father to go back and help the thief. Again the boy underscores perhaps the last bit of goodness left in the world. The boy is a Christ-figure who shows love and mercy to people that would do him harm in a world that is already dead.