The show is set in the year 2517 A.D., following the depletion of Earth's resources and an expansion of the human race into the frontier of outer space. The show takes its name from the "Firefly-class" starship operated by the central characters; the ship's class name is itself a reference to the appearance of the ship, whose tail section blinks during acceleration. Captain Malcolm "Mal" Reynolds is the veteran of a war of resistance against "The Alliance" - an organization that attempted to achieve the unification of all mankind under a single imperial government. A central "core" of planetary systems have fallen under Alliance control, while settlers and refugees in the farther reaches of space enjoy relative freedom from the long arm of the government but lack many of the amenities of a high-tech civilization. Mal now owns a small Firefly-class starship called Serenity, making cargo runs and performing various other tasks - legal or otherwise - to scrape together a living for himself and his crew.
Featuring a blend of elements from science fiction and western genres, the show depicts mankind's future in a way that is uncharacteristic of many contemporary science fiction programs. The dialogue and interplay between characters is central to the plot of the program, resulting in a story that is alternately serious and humorous.