The City of Ember is one of those science-fiction books that are constructed around the doomsday protection motif. Fearing an apocalyptic event, the Builders of Ember construct a mini-world underground for protection. Much as in The Giver, the leaders feel that the denizens of this world will not miss what they never have known, even natural light. However, the electrical system is beginning to fail, and odd things are happening.
Two youths named Doon and Lina begin to do some detective work after they graduate and are handed assigned jobs (which they switched with each other). For, one day Lina's baby sister has discovered and old piece of paper in a box. Evidently, there is a way out of the city, and some of the city leaders seem to be making plans for themselves. But, eventually, Lina enlists Doon in her efforts to break through the codes of the instructions that they put together, and they escape the traps that the corrupt mayor sets for them. In a boat that goes traverses an underground river, the youths come up to the earth and experience their first sunrise.
They lifted their faces to the astonishing warmth. The sky arched over them, a pale, clear blue. Lina felt as though a lid that had been on her all her life had been lifted off. Light and air rushed though her, making a song, like the songs of Ember, only it was a song of joy. She looked at Doon and saw that he was smiling and crying at the same time, and she realized that she was, too.
At last they are free and in a real world where they can pursue different paths and make choices about what they want to be. But, little sister Poppy has discovered something else: a journal. The youths learn that one hundred adults and one hundred children were sent to the City of Ember in order to preserve life. So, in order to preserve these lives further, Doon and Lina launch instructions over a cliff to an area where their friend Mrs. Munro, miraculously, stands. Mrs. Munro starts right away.