In this sequel to The City of Ember, DuPrau continues the adventures of Lina and Doon, who have led the 400 residents from the underground city of Ember to the unfamiliar world above. The refugees are tentatively welcomed, housed, and fed by the people of Sparks, located near the wasteland left by the long-ago Disaster that destroyed most of civilization. Conflicts arise between the two groups, mainly due to the differences between the sheltered, electric-powered life in Ember and the low-tech, farming-based existence in Sparks. As conflicts and violence escalate, Lina explores the wasteland and Doon finds himself caught up in the rhetoric of the militaristic and charismatic Tick. A dramatic conclusion brings the characters together and gives hope for the future of both groups, resolving the current conflicts but leaving room for future adventures.