When Lina and Doon get their assignments on graduation day and quickly trade jobs, they begin discovering secrets the city of Ember has been hiding for over 200 years. As a messenger, Lina takes information throughout the city to everyone from common citizens up to the mayor's office. Doon heads to the Pipeworks where learns about the labyrinth of underground tunnels and the slow deterioration of the city's generator.
Ember is a city - a small village, really - that is running low on everything. The supply rooms are running short of certain foods, clothing, light bulbs, and various other essentials. Worse, Ember has gone dark on numerous occasions. The city's lights go on at 6:00 am and off at 9:00 pm every day. Without those lights, there's no lights, and those lights have gone off during the day, sometimes for minutes at a time. People are going about their daily lives and suddenly... complete and utter darkness. Beyond the city limits is the Unknown Regions, a fancy name for "nothing."
Lina and Doon discover a mysterious box and an equally cryptic message. (It's not a mystery to readers, however. It's the directions out of Ember, as recorded by the Builders.) As they try to decipher the message, their jobs lead them to corruption in the city's government. Without the help of those responsible for the city, Lina and Doon go it alone, slowly understanding what the Builders' intentions were for the people of Ember.
As Lina and Doon learn more about the mysterious message, readers learn more about the mysterious city of Ember. While the city's leaders try to stop them, Lina and Doon seek to save themselves and all the people living in the city of Ember.
The story continues with The People of Sparks, and a prequel titled The Prophet of Yonwood. The fourth book, The Diamond of Darkhold, will be published in August, 2008.