PLOT: Set in space in 2507, the late lamented TV series Firefly is extended on the big screen with smart-ass Capt. Mal and his motley crew still playing at being Old West bandits and searching for meaning in life.

Legions of Browncoats -- the cultish fans of Joss Whedon's Firefly TV series -- are going galactic over Serenity, the big-screen extension of the show.

The Internet buzzes with "the signal" and the Browncoats, named for defeated freedom fighters in the backstory, gush over the stubborn Whedon's final triumph.

It is safe to assume that these devoted fans would give Serenity a five-star rave. For mere mortals, however, Serenity is a three-and-a-half star blast: Tons of genuine sci-fi fun thanks to the movie's sarcastic humour, well-drawn characters and action thrills that get started right off in a sensational prologue.

Whedon also earns full credit for his persistence. Firefly was trashed by the Fox TV network after only 11 of the original 14 episodes were aired in 2002.

The release of Firefly: The Complete Series on DVD in December, 2003, however, revived interest.

Even then, Whedon (best known for Buffy The Vampire Slayer and spin-off Angel) struggled to find a home, at Universal finally, for his feature debut as writer-director.

The result is no classic and is obviously flawed (including odd camera angles on close-ups), but well worth seeing. The nine key characters from Firefly return, performed by the same loyal-to-Whedon actors. It is a gonzo team led by brooding Nathan Fillion as the disgruntled Captain Malcolm (Mal) Reynolds.

While our anti-hero has some Han Solo, think Jesse James, the former Confederate guerrilla who went outlaw with brother Frank after the Union side crushed the South in the U.S. Civil War.

In Firefly, Reynolds went outlaw after the Alliance crushed the rebels and wiped out his platoon, all except the Captain and his buff sidekick Zoe (played by Gina Torres).

Whedon makes the Western motif blatantly obvious. Reynolds straps on what looks like a 19th century sidearm, and the dress code on the Serenity spaceship skews to the past, even though the timeline is 2507.

While the Old West in space twist is old news -- Star Trek and Star Wars took that path decades ago -- Whedon makes his motley crew so interesting, so likable and eccentric, that you can't help but love these goofs as they squabble their way through crime and stumble into heroic acts.

What the movie lacks, though, is an ultimate secret that has any Earth-shattering impact. Serenity goes to a hidden planet, and runs a gauntlet of cannibalistic Reavers, to find that secret. But it is not as big a deal as the movie makes it out to be. In fact, it is anti-climactic.

Hitchcock used to call those plot devices "a McGuffin" because he knew the journey was more important than the destination. That certainly applies here.

In Serenity, the epic journey is threatened by a truly terrifying Alliance operative, played brilliantly by English actor Chiwetel Ejiofor (Amistad).

Every hero -- even a reluctant one -- deserves a villain of equal powers. Serenity is in balance.

BOTTOM LINE: As sci-fi adventure, Joss Whedon's movie delivers. And you don't even need to have seen the TV series Firefly, although it would help.

(This film is rated 14-A)