This is a great movie (admittedly not as good as the series, but a fun watch nonetheless). You can get it for £3.79 delivered from ChoicesUK, which is the cheapest I have ever seen it!! It is from the maker of Buffy - Joss Whedon.
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Details: Captain Malcolm Reynolds, a hardened veteran who fought on the losing side of a galactic civil war, now ekes out a living pulling off small crimes and transporting passengers and cargo on the 'Firefly' class ship Serenity. He leads a small crew who are the closest thing he has left to family, insubordinate and undyingly loyal. When Mal agrees to transport a young doctor and his unstable, telepathic sister, he gets much more than he bargained for. The pair are fugitives from The Alliance - the coalition dominating the galaxy - who will stop at nothing to reclaim the girl. The crew that was once used to skimming the outskirts of the galaxy unnoticed suddenly finds itself caught between this unstoppable military force and Reavers - barbaric savages who roam the edges of space.