Even the most casual student of science fiction knows that when aliens from outer space visit Earth, they land either in a major American city, preferably New York or Washington, or in some remote cornfield or swamp, where they abduct and intimately examine a deputy sheriff or an inebriated farmer. The gigantic ship in "District 9," however, hovers over Johannesburg, South Africa, an even more unlikely place than Possum Droppings, Iowa, or Bad Breath, Arkansas, for the first encounter between humans and creatures from some unknown planet. That location demonstrates quite clearly the filmmakers' intention to create some parallels between their ostensible subject and the history of South Africa.

The film proceeds in a pseudo-documentary manner, interrupting its action with a series of interviews with the usual collection of talking heads - scientists, academics, reporters, etc. They provide, in the most natural and objective manner, the story of the visitation from an unknown planet - which occurred 20 years ago, when the ship appeared over the city, where it remains stationary in the sky. When the government sent teams up to the ship, they discovered a million sick and malnourished aliens, bipedal, vaguely humanoid creatures with tentacles for fingers and claws for mouths. Supposedly for humanitarian reasons, the government set up a huge camp for the visitors, who apparently live on welfare and tend to disgust the humans of the city, who call them "prawns."

Using the approach of a television news story, the camera follows the work of Wikus Van de Merwe (Sharlto Copley), a bureaucrat in the alien affairs agency, who supervises the government's evacuation and resettlement of the prawns to another district, further away from the city and its resentful inhabitants. Alternately silly and officious, Wikus leads a team of civilians and soldiers to inform the aliens of the plan, which leads to a series of strange and violent encounters. The prawns resist the order of eviction, often acting out in decidedly hostile ways - arguing in their clacking language, fighting, and vomiting or urinating on the officials.

Throughout the long sequence of the eviction, the movie intersperses reports of alien behaviors, which include a preference for raw meat, an addiction to canned cat food, and a propensity for criminality. Nobody, curiously, speculates about the origins of the space ship, the reasons for the journey to Earth, or the possibilities of some genuine relationship with the visitors. The aliens exist chiefly to supply an instance of human reactions to any outsiders, with obvious allusions to racism and South Africa's history of apartheid; the squalid sprawl of District 9 itself provides the most formidable proof of the film's real intent.

Within the context of alien encounters and racial references, the human story centers on the character of Wikus Van de Merwe. Through most of the film he talks to the camera, presumably operated by a television crew covering the eviction, describing his job, the general situation, the behavior of the prawns, touching now and then on his personal life. In the process of making some important discoveries about the aliens' technology, he suffers an injury and an infection that cause a strange metamorphosis, which transforms his whole being, bringing him illumination, understanding, and courage, while also destroying his former life.

"District 9" uses many of the formulas of its genre, borrowing material from a number of motion pictures, including such classics as "The Fly," "Alien," and "E.T."  It now and then falls into a pattern of repetitive action that threatens to reduce the movie to a series of action flick clichés, with a surprising amount of spraying blood, dismembered limbs, and exploding heads. Those images, along with numerous shots of flayed animals, chunks of meat, bloody body parts, and cannibalism, add a disturbing horror film motif to an otherwise unusual movie.

The cast of entirely unknown South African actors performs with conviction throughout, but Sharlto Copley's work as Wikus seems nothing less than extraordinary. Appearing in almost every scene, talking nervously to the camera, hesitantly attempting to establish his own authority, growing in strength of character and expanding in dimension before our eyes, he simply carries the emotional burden of the whole movie in a remarkable demonstration of acting in one of the most unusual science fiction films of this or any other year.