The City of Ember concludes with Lina and Doon having reached the surface from the cavern in which their city is built. They have written a note explaining how to leave Ember and flung it through a fissure far above the city. Now, joined by many of their compatriots, they travel across an empty land, eventually encountering the village of Sparks. Fortunately, the war feared by Ember's creators was, though horribly devastating, not the complete conflagration they had feared. There are some villages in the former California, Sparks being the most prosperous. The leadership and people of Sparks must contend with the unexpected drain on their resources posed by the larger group of Emberites, and both groups struggle to make sense of the other. Though there are plot lines about particular people and discoveries about the world, the story is centered on the ways in which economic tension increases in group/out group problems and leads to racist or excluding policies based on fear. The novel ends with a triumphant rediscovery and the promise of further emotional development for both Lina and Doon.