An excellent sci-fi show, set in space in 2517, focused on the crew of a Firefly class spaceship named Serenity.
The plot of the show revolves around two new passengers of the crew, a brilliant doctor named Simon Tam and his eccentric sister, River. Simon is avoiding arrest from the galactic federation of the Alliance for rescuing his sister from one of their institutions, where they were experimenting and testing with her brain.
Captain Malcolm Reynolds, played by Nathan Fillion, takes on the fugitive siblings, as he is one of the Independents, nicknamed the Browncoats, and harbors great resentment towards the Alliance.
This show is amazing in all aspects, but was cancelled by Fox after only 14 episodes, despite its large cult following. It remained cancelled although there was a huge call by avid fans for its return.
Almost impossibly, the show received so much support following its cancellation, a movie was created under the title Serenity, as a conclusion to the show.
If you haven't watched either the show or the movie, I strongly suggest you see one or both.
Link to Firefly's Wikipedia page
Link to Serenity's Wikipedia Page
Link to Firefly's Hulu page (has every episode)