Lina and Doon quickly come to realize that most of the adults in Ember are useless, clueless or downright evil.

In one of my favorite episodes of The Simpsons, the evil Mr. Burns plots to build a giant shield to block out the sun. That way, the citizens of Springfield will have to buy even more electricity generated by his nuclear power plant to replace the sunlight they've been getting for free.

The citizens of Ember are already in that situation: They live in a world without natural light and are entirely dependent on an ancient electrical generator that is prone to breakdowns. Their ancestors fled an unspecified apocalyptic event more than 200 years ago, and no one now living in Ember has knowledge of any other kind of life.

Not surprisingly, electrical power is an object of adoration in Ember. Schoolchildren pledge allegiance to the generator and the annual celebration includes a choir singing "When the light comes on, I will be with you."

You might think that a society so dependent on technology would cultivate scientific thought, but quite the opposite is true. Children are assigned by lottery to their adult roles at age 12, with no attempt to match talent with occupation. Adults have learned that it's best to not ask too many questions, and counsel young people to do likewise.

But lately things haven't been going well in Ember: Food's getting scarce and power blackouts are becoming more common. What the citizens don't know is that their city was only meant to last 200 years, and they're about 30 years past the due date. The knowledge necessary to save them is at hand, but they don't know how to use it.

Fortunately, not all the children of Ember do as they are told. Chief among the disobedient are Lina Mayfleet (Saoirse Ronan) and Doon Harrow (Harry Treadaway), classmates whose first visible act of rebellion is swapping their assigned jobs. Lina takes Doon's place as a messenger, dashing about town in a nifty red cape (costumes by Ruth Myers are an artful cross between medieval re-enactors and Welsh coal miners), while he applies his mechanical talents to working on the underground generator.

Lina and Doon quickly come to realize that most of the adults in Ember are useless, clueless or downright evil. But by pooling their talents, they begin to piece together the lost knowledge that could save the city. Of course, the powers that be, including the Mayor (Bill Murray) and his henchmen (Toby Jones and Mackenzie Crook), enjoy the status quo which allows them to exploit the citizens of Ember, so Lina and Doon must struggle against them as well as racing against time to save the city before the generator dies completely.

The marvelously detailed world of Ember was created through a combination of sets built on a brownfield in Belfast and CGI effects which blend in almost seamlessly; the only truly disappointing effect is a silly badger-like monster which patrols the generator tunnels. Production designer Martin Laing, director of photography Xavier Perez Grobet and art directors Jon Billington, James Foster and Ashleigh Jeffers present a world that is grungy and decrepit and yet simultaneously fascinating and enticing.

Some details are left out of the story, such as what caused people to move to Ember in the first place and why the mayor and his cronies don't have ptomaine poisoning from eating all that ancient canned food. These and other questions may be answered in the source material (City of Ember is based on the children's novel The City of Ember by Jeanne DuPrau), or it may be time to invoke the MST3K mantra: "It's just a show; I really should just relax."

Similarly, if you as an adult find yourself squirming at the obvious planting of clues or occasional warping of the time-space continuum, just remember: the source material was written for children in grades 4-8. Kids that age and younger will love it as an adventure story, while more experienced members of the audience can enjoy the skill with which the story is presented, as well as some deliciously campy acting by Bill Murray, Toby Jones and Martin Landau. Even better, the story of City of Ember has layers upon layers of meaning that could prompt to fruitful cross-generational discussions.

City of Ember has blockbuster written all over it, and it ends with a cliffhanger that practically screams "SEQUEL!" There are three other books in the series, so Lina and Doon may give Harry Potter a run for his money. | Sarah Boslaugh

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