Serenity is a film written and directed by Joss Whedon. It is set in the universe of the cancelled Fox science fiction television series Firefly, taking place six months after the events of the last episode . Like the television series that spawned it, Serenity is a science fiction Western, using elements of both genres. The film was released in the US on September 30, 2005.

Serenity is the story of the captain and crew of a transport and cargo ship 500 years in the future. Their lives of petty crime are interrupted by a psychic passenger who carries a dangerous secret.

The resources of Earth have been depleted, and humanity has moved to another star system and terraformed many of the planets. All the planets are controlled by the supposedly peace-loving yet still rather authoritarian Alliance. But a frontier justice still holds sway farther from the "core planets", where outlaws like the crew of Serenity can scrape out a living if they keep clear of Alliance forces and the Reavers, savage and cannibalistic humans who dwell beyond the outer planets and raid the Alliance worlds around the rim.

In order to earn her continued passage onboard Serenity, a fugitive from the Alliance, the telepathic River Tam (Summer Glau), accompanies Captain Malcolm Reynolds (Nathan Fillion), Jayne (Adam Baldwin), and Zoë (Gina Torres) on a mission to steal the payroll of an outer planet security company financed by the Alliance. During the robbery, the crew narrowly avoids capture by a Reaver raiding party when River is able to telepathically sense their approach. Wash (Alan Tudyk), the ship's pilot (and Zoë's husband) brings the ship to intercept the crew's surface vehicle, saving the crew from a grisly fate.

River's brother Simon (Sean Maher), the crew's doctor, angrily reacts to the captain's willingness to put his younger sister in such grave danger. Captain Reynolds responds by suggesting they leave at the next planet they land on, Beaumonde, where the crew expects to sell their loot. Simon agrees to the arrangement. The Tams do indeed disembark at Beaumonde, but while the captain haggles with the buyers, River suddenly starts attacking people in the same bar that the captain and Jayne are patronizing. Despite being a 90 pound (41 kg) girl, she manages to incapacitate everyone, including Jayne, and is about to shoot Captain Reynolds when Simon arrives and shouts a phrase in Russian, causing her to fall asleep.

Simon explains to the captain that, during her captivity by the Alliance, she was trained and conditioned to become an assassin. The only thing that can stop her after this conditioning has been triggered is the "safe-word" he uttered. Despite knowledge of this new danger and his anger at not being told about the possibility of carrying a potential living weapon, the captain allows Simon and River to continue traveling on Serenity.

The crew contacts Mr. Universe (David Krumholtz), a reclusive techno-geek who dwells with his robotic wife on a planet surrounded by an opaque ion cloud. After watching the security camera footage of the bar on Beaumonde, Mr. Universe discovers that River's outburst was triggered by a subliminal message in a seemingly harmless cartoon advertisement that had been broadcast all over the Alliance during the previous weeks. He tells the crew that before her attack, River had whispered the name "Miranda." He also notes that the footage has been viewed by someone else with high Alliance clearance.

Fearing Alliance pursuit, the crew takes refuge in the Haven mining colony with Shepherd Book (Ron Glass), a priest who once traveled with Serenity's crew. Book warns Mal that the Alliance agent pursuing River is likely to be an "Operative," and very dangerous. Shortly thereafter, the captain receives a call from Inara (Morena Baccarin), another former passenger. Their conversation is awkward but pleasant enough — with no arguing — leading Mal and Zoe to the conclusion that it's a trap, but they decide to visit Inara anyway. Mal's fears are realized; Inara is held hostage by a ruthless and nameless Operative (Chiwetel Ejiofor). The Operative offers to let the captain go on his way if he turns River over to him, but thanks to Inara's quick thinking, she and the captain escape the Operative and return to Serenity, which takes off undetected.

Another of River's outbursts shows the crew the meaning of "Miranda". It is the name of an outer rim planet, which had once been inhabited but was thought to be wiped out in a terraforming accident. River had subconsciously learned something mysterious about the planet when she came in telepathic contact with a member of the Alliance Parliament during her training. Traveling to Miranda to learn more would require crossing through what is now Reaver territory, which the crew members agree would be suicide, so instead Serenity returns to Haven and Shepherd Book.

On arrival, however, the crew discovers that the outpost has been ravaged by Alliance forces, and its inhabitants killed. Mal finds Book, who has shot down the attacking ship. However, he has been mortally wounded and dies in Mal's arms. Several other outposts that had harbored Serenity in the past have also been destroyed. Captain Reynolds receives a message from the Operative claiming responsibility, and promising more of the same until River is turned over.

Mal comes out and orders that Serenity be remodelled to look like a Reaver ship, which involves warpainting and mutilating the hull, making a dangerous modification to the engine, arming the weaponless cargo vessel with the settlers' cannon and tying bodies of the dead settlers to the prow. Everyone protests, but Mal furiously informs them that they can either do what he says or leave the ship now.

Serenity, now painted red and looking far more menacing, leaves for Miranda. The ship moves through a whole mass of Reaver vessels, and after an agonising wait, finally reaches the other side without incident.

Upon reaching Miranda, the crew discovers a normal, terraformed planet, with an earth-like environment which is completely habitable. The strange part is that the sprawling cities that dot the planet's surface are empty. Inside the buildings and cars are badly decomposed corpses, with no apparent cause of death. There are no signs of violence or disease. It is as if the people simply died.

The crew discover a log recorded by an Alliance research and rescue team after the disaster. The log recounts what has happened: the Alliance administered the chemical substance G-23 Paxilon Hydrochlorate, or simply "Pax", to the populace. It was supposed to remove aggression and thus render the planet free of violence. An unfortunate side effect was that the populace had stopped working, or eating, or caring about anything. They simply gave up on life and died in their newfound nonaggressive state. However, there was a small minority of the populace (approximately a tenth of a percent, thus given the planet's original population of 30,000,000 approximately 30,000 individuals) for which the drug had the opposite effect. They became extremely aggressive and mentally unstable, mutilating their own bodies, and killing the researchers who had come to investigate. They eventually left the planet and formed into the much feared Reavers. Thus, the Alliance was actually responsible for the creation of this menace.

Everyone is sickened by this revelation, but none more so than Mal. This was exactly the sort of thing that the Browncoats had been fighting to prevent: the Alliance's belief that they can make people "better"; that everyone must conform to them, regardless of the cost or consequence. For the first time in years, Mal is moved by something greater than himself; a belief, something he thought he'd lost in the Battle of Serenity Valley.

"This report is maybe twelve years old. Parliament buried it, and it stayed buried 'til River dug it up. This is what they feared she knew. And they were right to fear, 'cause there's a whole universe of folk who are gonna know it too. They're gonna see it. Somebody has to speak for these people. Y'all got on this boat for different reasons, but y'all comin' to the same place. So now I'm asking more of you than I have before. Maybe all. 'Cause as sure as I know anything I know this: they will try again. Maybe on another world, maybe on this very ground, swept clean. A year from now, ten, they'll swing back to the belief that they can make people... better. And I do not hold to that. So no more running. I aim to misbehave."

The plan is to reveal this secret to all the worlds by using the transmitter equipment belonging to Mr. Universe. Unfortunately, the Operative has predicted this, and is already waiting at Mr. Universe's headquarters, along with an Alliance fleet. When just about to leave Reaver territory, Serenity opens fire upon a Reaver ship. The ensuing chase by all the nearby Reaver warships causes the previously lone Serenity to emerge from Reaver space flanked by a large force of deadly Reaver ships. There is a massive battle between the two fleets, as Wash steers Serenity towards the planet with both the Alliance and the Reavers trying to destroy them as well as each other. During the attack, the Operative's ship is destroyed, but he flees the battle in an escape pod and follows the crew to the surface.

Serenity is followed by a Reaver ship, which fires an electro-magnetic pulse at them, disabling power. Wash is able to restore emergency power at the last minute and effect a crash landing. While Serenity suffers massive damage including having one of its engines torn off, it looks like the crew is out of danger. As everyone begins to relax, a Reaver harpoon suddenly smashes through the window, impaling Wash who dies instantly. Unfortunately for Wash, the cockpit was the only point that the Reaver harpooners could attack from the outside. There is no time to mourn and Mal pulls Zoë away from Wash's dead body just as another harpoon is fired into the cockpit. Fleeing Serenity to continue their assumed mission of getting the word out, the crew decides to set up a last stand in a small corridor to hold off the Reavers and give Mal the time he needs to make way to Mr. Universe and transmit the message.

Mal arrives to find Mr. Universe has been killed. However, before he died, he was able to leave a pre-recorded message with his robotic wife which informs Mal that there is a secondary transmitter in another area of the complex. Meanwhile the crew is losing ground to the Reavers and is forced to retreat when Zoë and Kaylee are injured. The Operative arrives on the planet and runs into the robotic wife, who repeats the message, informing him where the secondary transmitter is. The crew try to close the blast door, but it stops leaving a small opening. This buys them some time, but when the doctor is shot by a stray bullet, there is no one to tend to the injured. He tells them he needs his medical bag which he left in the preceding room. River leaps through the blast door, throws the medical kit back in, closes the door and is swarmed by the Reavers.

Mal reaches the second transmitter and finds that it is inconveniently located on a platform surrounded by a large drop. He is about to attempt to reach the platform when the Operative shows up. They have a stand-off, which results in Mal being quicker on the draw and shooting (but not killing) the Operative. Mal then proceeds to try and reach the transmitter, but the wounded Operative follows him. There is a fight between them with the Operative using a pressure point which is designed to completely disable his opponent — it fails, and has no effect on Mal due to nerves severed in an old war injury.

Mal does not kill the Operative, and instead disables him with a similar move and leaves him trussed up to watch the recording from Miranda. Returning to the crew, he is informed that River was trapped on the other side of the blast door with the Reavers — presumably killed. The door opens to reveal that, instead, River has killed all the Reavers. As she finishes, the Alliance troops enter, but instead of giving permission to shoot her, the Operative orders the squad to stand down.

After the crew buries the bodies of their friends Mr. Universe, Shepherd Book, and Wash on Haven, the crew patches up Serenity in a repair yard on the planet Persephone. Just as they are ready to leave, the Operative makes his own exit, promising Mal they will never encounter each other again. In the payoff to a subplot from both the series and the film, Simon and Kaylee finally make love. Zoe tells Mal that "she's tore up plenty, but she'll fly true," and Serenity heads back into outer space, with Mal in Wash's seat at the helm, and River acting as his copilot. The final shot shows the ship flying off triumphantly into the distance, until a random piece of metal flies from the back of the ship and hits the camera, prompting Mal's final, inquisitive line of "What was that?".

Jane Espenson, one of the writers of Buffy and Firefly, announced in June 2003 at a Buffy convention in the UK that Whedon was writing a script for a Firefly movie. Actors Nathan Fillion and Adam Baldwin confirmed this on the official Firefly forum, as did Whedon in several interviews. Universal Studios acquired the rights to Firefly.

On March 2, 2004, according to an article in Variety, the movie was officially greenlighted to enter production with a $40 million budget. Principal photography started on June 3, 2004. Joss Whedon said that the film would be released as Serenity, in order to differentiate it from the TV series. The 9 principal cast members from the television series (Adam Baldwin, Alan Tudyk, Gina Torres, Jewel Staite, Morena Baccarin, Nathan Fillion, Ron Glass, Sean Maher, and Summer Glau) all returned for the movie. On September 17, 2004 Joss Whedon announced on the official site that shooting had been completed

In addition to traditional advertising methods, Universal sought a few unique approaches to promoting the film. Hoping to generate buzz through early word-of-mouth, Universal launched an unprecedented 3-stage campaign to sneak-preview the movie in 35 US cities where the television series had earned high Nielsen Ratings. The first stage of screenings was held in 10 cities on May 5, 2005. The second stage, held on May 26, 2005, added an additional 20 cities and was also the source of controversy when individual theatres began selling tickets before the official announcement was released, leading some shows to be sold out before being announced. The third round of screenings, with an additional 5 cities, was held on June 23, 2005. The screenings proved a success, with all three stages selling out in less than 24 hours, the second-stage screening in DC sold out in a mere 22 minutes and the second screening in Phoenix sold out in 8.

Australian audiences were the first outside North America to get preview screenings. After an exclusive Sydney test screening, Melbourne held a public screening on July 21, 2005. This was followed by a film festival screening on the Gold Coast on July 22. Public preview screenings were held in Adelaide and Sydney on August 1, and Perth on August 4. Further screenings were held in Victoria, Tasmania, and Queensland in late August. Preview screenings were also held in the United Kingdom and Ireland on August 24, in London, Birmingham, Manchester and Dublin. Several of the screenings in all the countries featured the attendance of Joss Whedon and the film's cast, followed by a Q&A session with the audience. Whedon also attended two Q&A sessions after sold-out screenings of the finished film in Melbourne and Sydney on September 12 and 13.

Universal also utilized a viral marketing campaign, producing five short videos that were "released" on the internet between August 16 and September 5. These short films depicted excerpts of counselling sessions with the character River Tam while she was being held at a "learning facility" known only as "The Academy". The counsellor in these sessions is played by Joss Whedon himself. Taking place before the events of the movie or the television series, the videos shed some light on the experiments and torture "The Academy" conducted on River, "documenting" her change from a shy child prodigy to the mentally unstable character of the series. The clips can be found here. (The site's FAQ states that it was not involved with the making of these videos in any way.)

On October 5th, 2005, Universal made the first nine minutes of Serenity available online. A browser plugin allowed the viewer to see the opening of the film in full-screen broadcast quality (bandwidth permitting). The clip was removed a few weeks later.

Bridging the gap between the end of the television series and the beginning of the movie is a three-issue comic book series titled Serenity. The comic is written by Joss Whedon and Brett Matthews, illustrated by Will Conrad and Laura Martin, and published by Dark Horse Comics. The story focuses on the crew of Serenity taking a salvage job from Badger following a botched theft on a backwater planet, and the pursuit of River by the ominous blue-gloved men seen in the television series. The story is considered part of the Firefly/Serenity canon. Each issue of the series features three different covers, with each cover featuring one of the nine main characters, each by a different illustrator, including Joe Quesada, Bryan Hitch, Tim Bradstreet and John Cassaday. The first issue was published in July 2005, and the final one appeared in September. The comics quickly sold out on release, with both the #1 and #2 issues going into second printings. Many comic book retailers reported that it was their highest selling comic those months, in part because of the multiple covers, but also because it attracted a group of customers who are not traditionally comic book buyers.

Serenity is one of several movies set in the future that imagines how popular culture might evolve. Others include: Mad Max: Beyond Thunderdome, A Clockwork Orange and The Fifth Element.

This future envisioned in Serenity has two political and cultural centers: Euro-American and Chinese. Characters all speak English and Mandarin, with the latter language reserved for the strongest curse words and the most affectionate diminutives. Popular English in Serenity is a slang suggestive of the lost children of Mad Max Beyond Thunderdome. Where 21st century people might use "Neat" or "Cool," the characters in Serenity say "Shiny."