The Fourth World takes you inside slums on three continents to meet individuals caught up in the largest people migration in the history of the world. Understanding 'a billion people' is almost impossible, but meeting a handful of slum dwellers strips away the statistic and begins the process of building understanding.  Journey with the filmmakers to Guatemala, Kenya and the Philippines to meet slum dwellers. Listen to published experts--leaders in their fields from three more continents--as they bring understanding to the 'why' of slums, and foreshadow what's going to happen if the world ignores this social powder keg much longer.