An alien ship has parked itself over Johannesburg, South Africa in the early 1980s. The humans cut through the ship to find an alien race that is scared and malnourished. Then united relief organizations bring resources including food to take care of the alien race. Thus, District 9 is formed as a place of relief, but it eventually turns into a slum where the aliens live. Weapons are found and it becomes a dangerous zone. Then riots begin to breakout with the South African people demanding they leave the planet. The aliens begin causing damage to South African property and disrupting society, even killing people.
The South African government then hires Multinational United (MNU), a military group to remove the aliens and relocate them to a new location. Wikus is chosen to lead the relocation. He goes door to door to get the aliens to get them to sign eviction notices.
We find two aliens and a child alien searching for their alien technology because there is a fluid inside that they want. They are creating something that they’ve been working on for 20 years. Wikus goes into their shack and finds the canister with fluid inside and it sprays in Wikus’ face. Soon after Wikus throws up, then has black liquid dripping from his nose just before his fingernails begin to fall off. It appears he is falling apart from the inside out from the liquid.
We discover that the South African warlords have been collecting weapons from the aliens in exchange for cat food which the aliens love to eat. But the warlords aren’t able to use the weapons because it requires the DNA of the aliens to operate them. So, the warlords kill the aliens and eat them in order to find a way to operate the weapons. At home Wikus is getting worse and there is a birthday party for him, but he is so sick that he vomits black liquid all over the cake and has to be taken to the hospital. Once at the hospital the doctor removes the cast from his broken left arm to find that his hand has turned into an alien hand. MNU takes him from the hospital and begins to run tests on him. They learn that Wikus can fire the alien weapons and they begins to harvest his organs so that they can allow soldiers to use the advanced weaponry, but Wikus escapes from the testing facility and becomes the most valuable business asset on the planet.
Wikus hides in the alien refugee camp where he seeks a place to hide in the alien’s home who created the fluid. He makes an agreement with the alien to get the fluid for him so they can operate their ship and in return the alien will change Wikus back into a human. After they retrieve the fluid the alien tells him it will take 3 years to turn him back. Wikus arms himself with the alien weaponry and protects the alien and his son so that they can leave.
The alien and his son make it to the ship and Wikus is left behind in District 9 after killing all of the MNU soldiers. The alien ship leaves the planet and we find out that no one knows what happened to Wikus after that day. His wife receives flowers made out of metal. And in the last shot we see a Prawn crafting metal flowers; it’s Wikus fully transformed.