The movie City of Ember is based on the novel of the same name by Jeanne DuPrau. It takes place in a post-apocalyptic world where the city of Ember is the last bastion of civilization. The city's inhabitants are unaware of the outside world, and they believe that Ember is the only place left on Earth.
The story follows two teenagers, Lina Mayfleet and Doon Harrow, who live in Ember and discover that the city's power supply is running out. They also uncover a series of clues that lead them to believe that Ember was built as a temporary refuge for the people who built it, and that there is a way out of the city.
As the lights begin to flicker and the city descends into chaos, Lina and Doon embark on a perilous journey outside of Ember to find a way to save their city and the people they love. Along the way, they encounter a series of obstacles and challenges, including deadly creatures and treacherous terrain.
As they race against time to unravel the mystery of Ember, Lina and Doon learn the truth about their city's past and discover that their destiny lies in their own hands. The movie ends on a hopeful note, as the people of Ember begin to rebuild their world and prepare for a brighter future.