That's the first five minutes of the film, and I sat there thinking that if the rest was as interesting as the intro, City of Ember would be an enormously entertaining movie. And it is.

Not long after the time-lapse seal opens, the capsule is discovered by young Lina Mayfleet (Atonement's Saoirse Ronan). Just in time too: Ember's life-sustaining electricity generator is quickly dying, plunging the residents into occasional periods of frightening darkness. Lina shares her secret with friend Doon Harrow (Harry Treadaway) who is employed in the city's pipeworks, where his job is to help keep the decomposing system jerry-rigged together. They come to believe that the capsule contains instructions on how to get out of Ember. However, the adults - including Doon's pessimistic father (Tim Robbins) and the current corrupt mayor (Bill Murray) - don't want to hear anything about it, even if it seems more and more likely that the generator will collapse altogether. It's up to Lina and Doon to figure out the instructions and determine whether there really is a chance for life up there.

I'm a sucker for movies that create entire worlds and fill them with enough detail to let you get lost. This is one of them. I love the rotted, decaying look of Ember. (You'll feel like washing your hands as you watch.) It's claustrophobic, with tall buildings squeezed uncomfortably together, narrow streets, and people jostling for elbow room. Everything is rusty and old, with corrosion showing, as though the city is literally hanging on by a thread. Director Gil Kenan (Monster House) also gives you a sense of the desperation Ember's citizens face. In one chilling scene, the generator peters out for a few minutes, leaving everyone paralyzed with fear as things go pitch black. Can you imagine being deep underground and suddenly having all the lights go out, knowing that there was no escape? It gives me the creeps, as it does all the characters.

The sheer direness of the situation is compelling, but it's what City of Ember does with the admitted bleakness that makes it special. Without ever being too blunt, the story extols a very clear moral: Just because the adults think things are hopeless doesn't mean the children have to. Lina and Doon could easily resign themselves to their fate - everyone else has, after all - yet they don't. They cling to the idea that there's a way out. Nothing stops them. Not the evil machinations of the power-hungry mayor, not the despair of their loved ones, not even the prospect of facing the monstrous rodent that trolls around the pipeworks. It seems to me that a fundamental part of being a child is trying to make the world a better, more hopeful place than it was when the adults handed it to you. City of Ember shows us two young people refusing to inherit the pessimism of their elders.

Like one of my favorite movies, Dark City (which was also about a mysterious, self-contained metropolis), I suspect that City of Ember is going to be misunderstood in some quarters. Parents will say that family films are often bright and cheery, whereas this one is too dark and gloomy for children. Well, that's what is appropriate for the theme, and kids are more resilient with entertainment than they get credit for. Not only can they handle it, they will dig it. Others will gripe that, at 95 minutes, the movie is not long enough to delve deeply into the theme. I disagree strongly on that count. Too many of the recent family fantasy pictures have been infuriatingly bloated. (Hello, Prince Caspian!) This one moves along at a brisk clip, keeping you involved without needlessly belaboring anything.

I found City of Ember to be one of the most pleasant moviegoing surprises of the year. It deals with the line between desperation and hope, subtly reminding young viewers how important is to come down on the side of hope. That idea is conveyed in a way that’s imaginative, exciting, dramatic, and even fun. And in the end, isn't a story such as this much more valuable for young ones than a tale about a talking Chihuahua?

( 1/2 out of four)

City of Ember is rated PG for mild peril and some thematic elements. The running time is 1 hour and 35 minutes.