City of Ember

Twentieth Century Fox’s partnership with Walden Media, specializing in family-friendly fantasy productions, has yielded mixed results so far, both critically and commercially. “Nim’s Island” scored a hit, while “Mr. Magorium’s Wonder Emporium” failed to catch on, and “The Seeker: The Dark Is Rising” flopped entirely.

Will the tide turn with “City of Ember”? I’d like to think so. It’s a well-made adventure flick that ought to appeal to boys, girls, and their parents … if they notice it exists. Fox-Walden’s promotional department won’t exactly be winning any awards for boosting public awareness of their movies.

Based on Jeanne Duprau’s 2003 young adult novel, the story is set in an underground city where humans have dwelled ever since the surface of the Earth became uninhabitable (for reasons not mentioned). The original plan was for this to be a relatively temporary solution, lasting only 200 years, at which point things would be better and everyone could return topside. But now two centuries have come and gone, and the City of Ember’s leaders have forgotten their history and their purpose. No one remembers what the Builders (as they are called) had in mind when they built the city. No one knows what the plan was, or even that there was a plan.

And now Ember is in crisis. The generator that powers the city, an awe-inspiring piece of machinery that is the city’s heart as well as its sun, is on the fritz. Blackouts are frequent. The city’s pipes are falling apart, too, and the food supply is running out. This is because the Builders only designed everything to last 200 years, but the city’s succession of mayors dropped the ball at some point. The current leader, Mayor Cole (Bill Murray), is friendly but ineffectual, the sort of impotent bureaucrat whose best idea is to create a task force to investigate the blackouts.

It’s the generator — it should probably be capital-G Generator, given the reverence people have for it — that has the citizens most worried. They fear Ember is about to go black and never go back. Some people, like the blindly optimistic Mrs. Murdo (Mary Kay Place), insist that “the Builders will come again and show us the way.” Others, like the doubtful Loris Harrow (Tim Robbins), say that “the Builders abandoned us.”

Loris’ teenage son, Doon (Harry Treadaway), wants to make a difference in Ember, fervently hoping that when the post-graduation job assignments are made, he’ll be put to work on the Generator. His classmate, Lina Mayfleet (Saoirse Ronan, the horrible sister from “Atonement”), a descendant of one of Ember’s mayors, becomes Doon’s compatriot when she discovers an ancient box among her grandmother’s possessions. This box looks like the one that appears in the official mayoral portraits that decorate city hall, except that it’s missing from the most recent ones.

A city having crises both spiritual and practical, a mysterious magic box tucked away in an attic, conspiracies and secrets — those are the makings of a fine young-adult fantasy story. Unlike Walden’s “Chronicles of Narnia” productions, the religious and political metaphors here are not overstated or underlined. Teenager viewers might enjoy discussing their implications, while younger viewers can disregard them entirely and just enjoy the adventurous story.

Directed by Gil Kenan (“Monster House”) from a screenplay adaptation by Caroline Thompson (“The Nightmare Before Christmas,” “Corpse Bride”), the film boasts a stylish art-deco-inspired production design and plenty of engaging twists and turns in the plot. It loses some luster in its last act, when the story becomes rather commonplace and the action starts to resemble a Disneyland ride, but the lively performances by the young leads, Harry Treadaway and Saoirse Ronan, keep things buoyant, as does Bill Murray’s very likable turn as the idiot mayor. The Builders have done a fine job here, if only audiences will show up to appreciate it.

B (1 hr., 35 min.; PG, mild thematic elements, a little scariness.)