The lights are flickering and Ember is slowly dying, but the small, hermetic society it contains has no idea how to escape -- doesn't know there's anyplace to escape to. The surface world has been forgotten, even if our heroine, Lina Mayfleet (Saoirse Ronan, the changeling child from "Atonement") draws landscapes with skies, as if from genetic memory.
She and rangy young Doon Harrow (Harry Treadaway) find a key to the way out when Lina comes upon a metallic box created by "the builders" when Ember was established. It provides exit instructions, and as the two dash about the crumbling cityscape trying to put the pieces together, you may feel as if you've wandered into the old computer game "Myst."
The movie's production design is the real star, mulching "Metropolis," steampunk, Charles Dickens, and "The Matrix" into one beguilingly grotty underground universe. The human stars are overshadowed by all the clockworks. Murray makes an amusing moral slug of a mayor before he has to become a two-dimensional villain, and Tim Robbins, Martin Landau, Mary Kay Place, Mackenzie Crook, and Marianne Jean-Baptiste (as the only person of color in town; how'd those genetics work out?) take a back seat to the heavy-breathing plot and distressed ambience.
Much of the movie's small budget seems to have gone to the digital creation of giant mutant animals not in the book (you'll never look at a star-nosed mole the same way). For all its missed chances, though, "City of Ember" still casts a neat glow. The story's powered by the sense of discovery that moves classic quest tales -- the idea that there's something much, much bigger out there if only you can find it. It's a modest movie that understands the sky's the limit.
Ty Burr can be reached at tburr@globe.com.
