The setup for this sci-fi adventure is delicious: 20 years after a massive spaceship has descended from the heavens, stalling over Johannesburg like some intergalactic junker, its insectlike passengers inhabit a squalid slum called District 9, while a Blackwater-style corporation tries without success to crack the technological secrets of their advanced weaponry. The parallels to racial apartheid aren't exactly subtle, but the mockumentary frame allows for plenty of talking-head segments that sketch out a satirical alternate history. Unfortunately, as in many such big-screen comic books, the backstory beats the hell out of the present-tense plot, a routine affair in which a well-meaning doofus working for the Man is infected with a virus, starts turning into an alien himself, and falls in with the oppressed creatures. Backed by Lord of the Rings producer-director Peter Jackson, Neill Blomkamp, a South African director of TV commercials, adapted his short Alive in Joburg. R, 112 min.