Appearing in the comic book miniseries Serenity: Those Left Behind and the film of the same name, the nameless and rankless Operative is the principal antagonist in the film. He is portrayed by Chiwetel Ejiofor. With no name or rank, he claims that he does not officially exist.
In the Firefly universe, an operative is an agent of the Alliance government. Similar to a black ops agent, operatives do work that isn't specifically acknowledged by the government. Operatives technically don't exist; they give up their names upon becoming operatives, and they don't hold an official rank in the Alliance. However, their status as an operative can get them access to most Alliance facilities as well as respect from those who know what an operative is. Operatives are highly trained in close combat as well as combat with weapons. They are extremely devoted to their cause; they often are asked to do questionable things, and yet they never ask questions.
Working directly for the Parliament of the Alliance, The Operative single-mindedly hunts down River Tam because he believes that his actions "make the world a better place". He is shown to have little problem with killing as part of his job, ruthlessly murdering several people using his sword, and also ordering the attacks that were responsible for the death of, among others, Derrial Book. While the Operative may find the killing of an innocent girl wrong, he believes that he is serving a greater good by killing her. He dreams of "a world without sin", and the only way to attain that world is by doing whatever the Alliance asks him to do.
The Operative's weapon of choice is a sword. He sees it as being more of a civilized and classic method of killing, and prefers to use it as opposed to guns. He often tries to paralyze his targets by taking out a nerve cluster near their waist, and then stabs them; on some occasions, he has his enemies fall forward on to his sword, much like disgraced Roman generals used to do. He will use firearms when he has to, but they tend to be a last resort. In addition to his weapon and hand-to-hand training, the Operative is dangerous due to his resolve. He truly believes that what he is doing is right, and yet he has no delusions about the evils of it. He admits to Malcolm Reynolds that he is a monster and he can never live in the world he is helping to create.
Eventually, the Operative discovers that the secret River Tam possesses, and he is trying to protect, has been passed to Mal. In attempt to finally end the problem, the Operative fights Mal atop a large suspended computer terminal. Mal manages to give the Operative doubts about his mission by forcing him to watch a report by another Alliance officer, revealing that it was the Alliance itself that had been responsible for accidentally creating the Reavers during their attempt to calm the population of the planet Miranda. When Mal broadcasts the secret to the universe, the Operative admits defeat and decides to leave the Alliance (Although it is implied at the end of the film that he subsequently committs suicide).