Serenity is based on Joss Whedons television show Firefly, in which interplanetary travel has brought about colonization of the planets, leading to a combination of sci-fi and Western tropes. The film picks up where the short-lived series left off, following the exploits of a crew of small-time criminals and outcasts who eke out a living on the edge of space, performing illegal smuggles and transports aboard a Firefly class cargo ship named Serenity. Led by a quick-witted veteran from the losing side of an interstellar war, Captain Mal Reynolds (Nathan Fillion), the crew is comprised of a rag-tag assortment of characters who, despite having their differences, are mostly loyal to one another, the closest thing that many of them have to a family. The stability of the crew is challenged, however, by the revelation that two of the passengers aboard, a brother and sister, are fugitives, wanted by the Interplanetary Alliance with a hefty reward on their heads. The young woman, River (Summer Glau), who was held captive in a government facility, has since developed unimaginable combat skills and telepathic abilities. She appears to have been altered by some form of experimental technology, leaving her emotionally unstable and incalculably valuable. The ship therefore remains on the outskirts of space, keeping it under the radar of the Alliance but placing the crew in danger of being sacked by Reavers -- savage men who traverse the edge of space, turning hapless goers by into food and clothing. They cannot run forever and now, the crew of Serenity must risk everything and rely on each other to keep River out of government hands and their ship in one piece. One question, however, haunts the crew throughout their ordeal: is River herself more of a threat to them than any of the enemies that pursue them? Serenity mixes action with humor and relies on the casts strong chemistry as portrayed through the characters steady rapport. ~ Cammila Albertson, All Movie Guide