The film is a continuation of Whedon's short-lived 2002 Fox television series Firefly and stars the same cast, taking place after the events of the final episode.

The film stars Nathan Fillion, Alan Tudyk, Adam Baldwin, Summer Glau and Chiwetel Ejiofor.

Once there, however, a subliminal message in a television commercial causes River to attack numerous bar patrons, and Mal takes the siblings back aboard the ship.

The crew contacts reclusive hacker Mr. Universe, who discovers the message designed to trigger River's mental conditioning.

They find its 30 million colonists dead, and a recording that explains an experimental chemical to suppress aggression had been added into Miranda's atmosphere.

He tells Mal the broadcast has weakened the Alliance government, but while he will try to convince the Parliament that River and Simon are no longer threats, he warns that they may continue their pursuit in retribution for getting the word out.

The film is based on Firefly, a television series canceled by the Fox Broadcasting Company in December 2002, after 11 of its 14 produced episodes had aired.

Whedon felt that the strong sales of the Firefly DVD, which sold out in less than 24 hours after the pre-order announcement,[10] "definitely helped light a fire and make them [Universal] go, 'Okay, we've really got something here.'

[12] All nine principal cast members from the television series were scheduled to return for the movie, but Glass and Tudyk could not commit to sequels, leading to the death of their characters in the second draft of the script.

[4] Principal photography for Serenity was originally estimated to require 80 days, lasting a typical 12 to 14 hours each, with a budget of over $100 million.

[16] The sequence where the crew is pursued by Reavers after a bank robbery was filmed along the Templin Highway north of Santa Clarita.

[21] For budgetary reasons, a gimbal and CGI, much like those used in the pod race in Star Wars: Episode I – The Phantom Menace, were quickly ruled out.

[15] Instead, the crew fashioned a trailer with a cantilevered arm attached to the "hovercraft" and shot the scene while riding up Templin Highway north of Santa Clarita.

However, he did not want to step too far into Western clichés to "cause justified derision" and hoped the score would also draw from Chinese and other Asian musical elements.

He cautioned against vocal orchestration, believing there to be only two voices in Hollywood and wishing to avoid both, and advised moderation in woodwind, feeling wind instruments to be "either too airy or too sophisticated".

Whedon's instructions to Newman for the ship Serenity's theme was something homemade and mournful, evoking the idea of pioneers who had only what they could carry.

Serenity became the first film to fully conform to Digital Cinema Initiatives specifications, marking "a major milestone in the move toward all-digital projection".

A rough cut of the film was previewed in a total of thirty-five North American cities where the Firefly television series received the highest Nielsen ratings.

[46] Bonus features on the DVD version include audio commentary from Whedon; deleted scenes and outtakes; a short introduction by Whedon for advance screenings; a hidden featurette on the creation of the Fruity Oaty Bar commercial; and three featurettes on the Firefly and Serenity universe, special effects, and the revival of the television series to film.

[2] Movie industry analyst Brandon Gray described Serenity's box office performance as "like a below average genre picture".

[64] Roger Ebert, in his review for the Chicago Sun-Times, gave the film three out of four stars, commenting that it is "made of dubious but energetic special effects, breathless velocity, much imagination, some sly verbal wit and a little political satire".

[65] Peter Hartlaub in the San Francisco Chronicle called it "a triumph", comparing its writing to the best Star Trek episodes.

"[68] USA Today film critic Claudia Puig wrote that "the characters are generally uninteresting and one-dimensional, and the futuristic Western-style plot grows tedious".

[76] IGN Film awarded Serenity Best Sci-Fi,[77] Best Story,[78] and Best Trailer for the year,[79] and it won second for Overall Best Movie after Batman Begins.

[82][83] NASA astronaut Steven Swanson, an ardent fan of the series,[84] took the Region 1 Firefly and Serenity DVDs with him on Space Shuttle Atlantis' STS-117 mission, which lifted off on Friday June 8, 2007, to be added to the ISS entertainment library.

[85] On February 20, 2009, NASA announced an online poll to name Node 3 of the ISS; NASA-suggested options included Earthrise, Legacy, Serenity, and Venture.

A novelization of the film was written by Keith DeCandido and published by Simon & Schuster under their Pocket Star imprint on August 30, 2005.

[103] Diamond Select Toys released five six-inch action figures initially featuring Malcolm Reynolds, Jayne Cobb, and a Reaver,[98][104][105] later adding River Tam,[106] Inara Serra,[107] and Zoe Washburne.

[117][118] The first major sequel rumor began on December 1, 2005, when IGN Filmforce reported that Universal had expressed an interest in making a Serenity television movie for broadcast on the Sci-Fi Channel.

[121] In an interview at the 2007 Comic-Con, Whedon stated that he believes hope for a sequel rests in the sales of the Collector's Edition DVD.