City of Ember by 20th Century Fox

For centuries, the residents of the underground City of Ember have flourished in an amazing world of glittering lights and quiet containment. But when the City's massive power generator begins to fail, the street lamps begin to fade, along with the hopes and dreams of the townspeople. Now it's up to two courageous teenagers to follow a trail of clues left behind by the ancient Budders and find a way out of Ember before their world is plunged into darkness forever.