In 1982, a large unidentified flying object hovers above Johannesburg, South Africa. Reports suggest that the craft became stranded and dropped to Earth after a command module separated from it and was nowhere to be found. An exploratory team discovers a group of one million unhealthy and leaderless members of an arthropod-like extraterrestrial species who are given asylum on Earth. Some of these aliens engage in criminal and destructive activities, which lead to demands from the human population for more control. As a result, the aliens, derogatorily referred to as "prawns", are confined to a government camp inside Johannesburg, called District 9. The camp is secured and, with a massive police presence, soon turns into a slum. In the first decade of the 21st century, Multinational United (MNU) is placed in charge of policing and relocating the now 1.8 million aliens to District 10, a new camp 200 kilometres outside of Johannesburg. They use a private military corporation, headed by Koobus Venter (David James), to enforce the relocation effort with impunity.
Wikus Van De Merwe (Sharlto Copley), an MNU field operative, leads the relocation with the serving of eviction notices on August 9, 2010. During the eviction Wikus confiscates alien weaponry and "aborts" their eggs. As this continues, some nearby aliens are shown distilling a mysterious fluid, into a small canister. One of the aliens designated as Christopher Johnson (voiced by Jason Cope), resists. While raiding the shack of the alien that was helping Johnson, Wikus discovers and removes the container, accidentally spraying some of the liquid onto his face; and his left forearm is also injured by one of the aliens. Consequently, Wikus begins to feels sick and sees his fingernails loosen. That night, he falls ill and is taken to a hospital, where his left forearm is revealed to have mutated into an alien appendage. He is immediately taken into MNU custody. After discovering that Wikus can now operate alien weaponry due to his mutating DNA (the weapons being unresponsive to humans), they force him to test various energy weapons, including against a live alien target. The scientists then intend to vivisect him before he fully transforms, but a panicked Wikus overpowers his captors and escapes.
Now a fugitive, Wikus takes refuge in District 9 and returns to Johnson's shack. Noticing Wikus' arm, Johnson reveals that the canister contains a fluid that he gathered over 20 years by scavenging, which would allow him to reactivate the dormant mothership. After revealing the location of the lost command module hidden under his shack, Johnson agrees to help reverse Wikus' genetic transformation if Wikus retrieves the canister from MNU. Wikus agrees and tries to buy weapons from a local Nigerian gang. Their leader, the paralyzed warlord Obesandjo (Eugene Khumbanyiwa), abducts Wikus, seeking to gain his ability to operate alien weapons. Wikus finds an alien firearm and kills some of Obesandjo's men before stealing a cache of weapons and escaping.
Wikus and Johnson break into the MNU offices and retrieve the canister, fleeing back to District 9. Johnson, having just seen that MNU is performing medical experiments on his fellow aliens, tells Wikus that he will not let his people be experimented on and informs Wikus that he will seek help for the other members of his species before curing him, which would take three years. Enraged, Wikus knocks Johnson unconscious and powers up the command module. Soon after takeoff, one of the craft's engines is shot off by an MNU missile battery and it quickly crashes nearby.
MNU forces enter District 9 taking Wikus and Johnson prisoners, but Obesandjo's gang ambushes them. During an intense fire fight the Nigerian gang captures Wikus. From the downed command module, Johnson's son activates the mothership and an alien mechanized battle suit which frees Wikus. Wikus pilots the suit and rescues Johnson. Promising Wikus that he will return to reverse his transformation, Johnson activates a tractor beam in the mothership, which lifts the stricken command module towards it. Heavily wounded and in a much more advanced state of his mutation, Wikus crawls out of the wrecked battle suit to be confronted by Venter. Just as he tries to kill Wikus, several aliens appear and tear Venter apart.
The mothership begins to leave as Johannesburg's residents celebrate its departure. A series of interviews and news broadcasts show the aliens have successfully moved to District 10, and are said to have a population of 2.5 million and growing. MNU's illegal experiments on aliens are exposed. Those interviewed theorize about Wikus' fate and hypothesize that Johnson might return for the refugees or declare war on humanity. Wikus' wife reveals that, having found a small metal flower on her doorstep, she has hope that her husband is still alive. In a scrapyard, an alien with a bandaged left arm and a single blue eye is seen crafting a flower out of metal.
http://www.youtube.com/watch?v=d6PDlMggROA
