After fighting on the losing side of a civil war, Captain Malcolm Reynolds (Nathan Fillion) and his crew of the ship Serenity scrape by as a small-time crooks and transportation for hire, laying low on the outskirts of a galaxy ruled by the Universal Alliance. When Reynolds and his crew pick up a young doctor, Simon (Sean Maher), and his telepathic sister, River (Summer Glau) they get a lot more than a couple of passengers. It seems River stumbled onto a secret the Alliance doesn't want anyone to know, and...