Devoted fans of "Firefly," the short-lived show from cult TV guru Josh Whedon ("Buffy," "Angel"), will likely go crazy for this big screen version, but the results are decidedly more mixed for the rest of us.

Serenity is set in a future some 500 years from now, and follows a band of misfit rebels as they're chased across the universe by the Alliance, an oppressive coalition government that wants to get its hands on River (Summer Glau), a powerful, 17-year-old psychic traveling with the rebels. The storyline has even more interesting complications and convolutions, but the film doesn't really tie them together in a cohesive, satisfying way, and Serenity tends to lurch ahead in a curiously clunky, episodic manner that seems more suited to the small screen than to the big one. The dialogue is frequently clever, but most of the characters tend to talk and act either like ancient samurais or, mostly, like cowboys (as Whedon openly admits, the concept here is basically an old fashioned western in space — although there are obvious traces of all the usual sci-fi signposts as well, from "Star Trek" to Star Wars to Bladerunner). Serenity is a touch darker than most of its influences, however, although it ultimately shies away from getting too deep into that darkness or into its characters, many of whom seem at a glance to be fairly interesting. Also stars Nathan Fillion, Gina Torres, Chiwetel Ejiofor, Morena Baccarin, Adam Baldwin and Sean Maher.

Serenity (PG-13) opens Sept. 30 at local theaters. 3 stars.