In an alternate 1982, a huge alien spaceship arrives on Earth and hovers above South Africa.
For three months there's no activity from the ship, so the authorities finally decide
to cut their way inside, only to discover a group of aliens in a malnourished condition
because they ran out of supplies a long time ago.
These aliens get derogatorily named "prawns" by humans.
Rumors say a shuttle descended from the mothership, but nobody is able to find it.
After receiving lots of international pressure, the South African government moves 1.8 million
prawns to a refugee camp known as "District 9".
Scholars believe these prawns are the workers of their species, and therefore they need
higher leaders to command them and rarely take initiative.
Although it's surrounded by soldiers and fences, the first few months in the district are peaceful,
and it's discovered aliens love cat food.
But as time passes, humans begin rioting because the government is using too many resources
on aliens instead of taking care of their people, and District 9 becomes a slum, further
gaining people's xenophobia.
The fact the aliens see certain violent activities, like setting fire to vehicles, as mere entertainment
doesn't help their case at all.
Eventually the area becomes overcrowded and a prime land for all kinds of crime.
Warlord Obesandjo opens a massive black market in District 9, which includes lady workers
and arms trafficking.
The alien's technology is quite advanced, however human hands aren't capable of handling
their weapons.
Twenty-eight years later, the tension between aliens and locals make the government relent
to public pressure, and they decide to move the camp away from the city to a remote location.
To do so they hire a weapons manufacturer called MNU, Multinational United, whose executive
Mr. Smit appoints his employee and son-in-law Wikus to lead the relocation.
A group of mercenaries will also come along for the sake of Wikus' safety and to push
along any aliens that resists, Wikus' assistant and a cameraman also come along to record
it all.
While they get ready, Wikus isn't happy to see how many weapons the mercenaries have
brought, but Colonel Venter insults him and tells him to deal with it.
A whole convoy of vehicles carry the team to the district to be able to cross through
he protests, and when a few prawns try to attack them, the mercenaries defend themselves
with killing shots.
Wikus goes from door to door asking the prawns to sign the forms that informs them of them
eviction, sometimes using cat food as bargain.
While some aliens accept to cooperate, others don't want to be taken from their homes and
try to fight, which causes the mercenaries to take them out by force despite Wikus' protests.
In one of the houses they find prawn eggs filling the room from wall to wall, and after
showing them to the camera, Wikus orders a mercenary to burn them.
The shacks also contain lots of hidden alien technology that the mercenaries confiscate
for the MNU to continue testing even if they haven't figured it out yet.
Meanwhile, Christoper, his son CJ, and his friend Paul are seeking a special alien fluid
from destroyed prawn technology that piles up with the trash.
CJ finally finds a piece after two decades, and the group excitedly takes it to their
home, where they take the fluid to a hidden room filled with advanced tech.
The fluid is synthesized and put inside a silver cylinder to carry on their plan, but
at that moment, Wikus and his team knock on the door.
Christopher and CJ rush to their own house, and after hiding the cylinder, Paul goes out
to deal with the humans.
However since Paul doesn’t want to cooperate, the mercenaries quickly push him to the ground
and hold him at gun point.
Wikus enters the house to investigate and finds lost of weapons plus the cylinder, which
he accidentally activates and causes it to spray his face.
After confiscating the cylinder, Wikus tries to ask Paul some questions, but Paul responds
by hurling the mercenary into his house and pushing Wikus onto a barrel of fire.
Venter arrives with more men and immediately kill Paul while Wikus discovers he's burned
his arm.
After receiving medical attention, Wikus continues with his duty, and eventually makes it to
Christopher's house.
He tries to give some candy to CJ, but CJ responds by throwing it at him.
This reaction angers the humans, who decide to push Christopher to his knees and inspect
the house, where they discover all sorts of equipment.
While looking around, Wikus suddenly throws up a lot of weird liquid and begins feeling
dizzy.
The team decides to take him away for now, but when they stop to grab a bite, Wikus'
nose begins bleeding.
More symptoms keep appearing when Wikus returns to the office to do his reports: he won't
stop coughing, and his nails are coming out of his fingers.
Back in the district, Christopher and CJ look for the cylinder and get sad when they find
it gone.
Meanwhile a group of prawns trades their battle suit for a bunch of cat food at the warlord's
base, however one of the men kills a prawn to use him as food.
Obesandjo has been hiring witches and shamans because he wants to become a prawn to be able
to use their weapons, and these witches think that can be achieved if he consumes prawn
flesh.
However so far it hasn't worked.
Sometime later, Wikus returns home to discover his wife Tania is throwing him a surprise
party to celebrate his promotion.
Wikus tries to be social and friendly, but he isn't feeling well at all.
He ends up in the bathroom throwing up in the sink, and when they cut the cake, he throws
up again before passing out.
The next morning, Wikus wakes up in the hospital.
The doctor removes the bandages from his burned arm, only to discover Wikus' hand has become
a prawn claw.
Terrified, the doctor calls the MNU, and a bunch of soldiers quickly arrive to take Wikus'
body away in a bag while ignoring Tania's pleas for an explanation.
Later at a lab, the staff finds the cylinder in Wikus' pocket and they take it away.
From then on, the MNU puts Wikus through a series of brutal experiments, including trying
out alien technology.
To Wikus' surprise, his new hand has enough prawn DNA to use the alien weapons.
Wikus suffers as they make him shoot various targets and at the end, he also has to shoot
a prawn to death, which mentally destroys him.
Once the tests are over, the scientists and the executives, including Smit himself, agree
to kill Wikus in order to harvest his organs and blood before he finishes transforming
into a prawn.
With DNA composed of the perfect prawn and human balance, they could create great soldiers
capable of using the alien weapons.
When he hears this, Wikus freaks out and attacks everyone around him, using a scalpel to get
a hostage so he's able to escape the lab before he's shot.
The mercenaries are ordered to go after him, and Smit meets with Tania to give her a twisted
version of what's going on.
On the streets, Wikus steals clothes from hangers, a phone from a kid, and scavenges
trash cans for food while always trying to keep his claw hidden.
He tries to call his friends and family to ask for help, but everyone ignores him, and
soon he learns why: when he enters a store, he sees a new broadcast announcing he's wanted
fugitive that developed a transmissible disease from doing the dirty with the prawns.
Everyone in the shop runs away from him, and Wikus accepts he has no choice but to go to
District 9.
Here he scavenges as well and even manages to obtain a can of cat food, which he eats
eagerly until he realizes he's losing his teeth as well.
At that moment, Wikus receives a call from Tania, who informs him she doesn't want anything
to do with him anymore because he disgusts her.
Tania ends the call without hearing his explanation, and Wiku is so desperate to get her back that
he gets an ax to try to get rid of the claw.
However he's so nervous that he only gets one finger, and the pain is too much to continue.
Suddenly, mercenaries' helicopters begin looking for him in the area.
Wikus rushes to hide inside a house and bumps into Christopher, discovering his secret room
right before passing out from blood loss from his wound.
When he wakes up later, he finds himself inside the rumored shuttle hidden under Christopher's
house.
When Wikus explains he doesn't have the cylinder anymore, Christopher and CJ explain they need
the fluid to operate the mothership again, and it could also power a machine that can
help Wikus reverse his transformation.
Retrieving the cylinder would be impossible because the mercenaries would kill them on
the spot.
Wikus spends the following hours suffering the pain of his body transforming as his skin
sheds and his torso mutates.
Suddenly Wikus gets another call from Tania, and this time she promises to take him back
and to be more understanding.
However this is a trap by the MNU, who made Tania call with lies to track Wikus' location.
Meanwhile CJ tells Christopher how much he misses his home planet, but Christopher reminds
him they can't go anywhere without the fluid, so they should go to the new settlement.
Wikus overhears this and feels bad for them so he explains the new territory is even worse
than this one, going there is just a bad idea.
Desperate to help the prawns and go back to his wife in a better state, Wikus announces
he has a plan.
Afterward Wikus goes to see Obesandjo to try to buy some weapons, but he's received with
disdain and violence.
When the men push Wikus they notice his transformed body, and Obesandjo sends orders to get his
claw for him to eat.
Wikus struggles against the men and finds an alien weapon on the ground, which he immediately
takes and begins shooting around.
Its power is incredible and quickly kills a bunch of men, allowing him to grab a bag
of weapons and escape.
Meanwhile the mercenaries arrive at Christopher's shack, only to find it empty.
It turns out Christopher and Wikus are sneaking into the MNU base by blowing up the entrance,
and as soon as they arrive at the lab, they shoot a few men before finding the cylinder.
However Christopher also finds many prawns that have been killed in experiments, including
Paul.
The shock doesn't let him move, and this gives the mercenaries time to catch up with them
and open fire.
Wikus fires back and kills lots of mercenaries while he reminds Christopher of CJ's future,
which helps the prawn snap out of it.
Then Christopher uses scraps found around the lab to make a bomb, which is used to create
an opening on the wall.
Wikus and Christopher rush outside and steal a MNU car to return to District 9 while Venter
and his men follow him.
Once they make it to the house, CJ begins putting the fluid in the shuttle, and Christopher
uses that moment to confess he'll come back in three years to cure Wikus because the current
fluid isn't enough to both power the shuttle and the healing machine.
Furious, Wikus knocks out Christopher and descends into the shuttle, where CJ is putting
the fluid into the shuttle and makes the shuttle work again.
A desperate Wikus tries to operate the shuttle while Venter arrives and threatens to kill
Christopher.
Suddenly the ground starts to shake and Venter and Christopher run out of the house right
before the shuttle raises from the ground not very smoothly.
Venter orders his men to open fire, and a missile immediately destroys one of the shuttle's
engines, so Christopher has to watch how his last hope crashes to the ground.
Afterward, Venter's men capture Christopher and Wikus to take them away in their car.
However the vehicle is suddenly ambushed by Obesandjo's gang, causing their cars to crash
against Venter's.
Then the gang opens fire and fiercely fight against the mercenaries until they grab Wikus,
taking him away while leaving Christopher behind.
Meanwhile CJ deals with the shuttle panel and manages to activate the mothership again.
At the gang's base, Wikus is taken to the witches to try to perform the ritual using
his claw.
However when CJ activates the mothership, this also activates all other alien tech,
including the battle suit hidden in the gang's base.
The suit scans the area and detects Wikus as a prawn ally but the gang members as human
enemies, so it opens fire to kill Obesandjo and his entire gang.
Back to the mercenaries, a few of them interrogate Christopher about the revived mothership while
the rest of the group goes after Wikus.
Finding himself surrounded, Wikus has no choice but to put on the suit and meet them face
to face.
When he notices the mercenaries captured Christopher, he offers to trade the alien for exchange
of his freedom, however he quickly changes his mind when he hears Venter order his men
to kill Christopher.
Furious, Wikus begin killing mercenaries with no mercy in order to save Christopher.
Then they rush back to the shuttle, but since more mercenaries are coming after them, Wikus
stay behind to buy Christopher time, refusing to come when Christopher invites him to his
planet.
As thanks, the prawn promises to return in three years to cure him.
Wikus keeps on killing mercenaries all over the place, spilling blood everywhere, flipping
a car when it comes after him, and even shooting a few missiles.
When he's about to shoot Venter too, a car hits him from behind and he falls with the
suit malfunctioning.
At that moment Christopher contacts the mothership through the shuttle control panel, and makes
the mothership extract the shuttle so he and CJ and escape.
The mothership emits a tractor beam and picks up the shuttle, Venter sees this and orders
for another missile to be fired.
Wikus immediately cuts in and uses his suit to grab the missile, which explodes and destroys
his left arm.
Seeing Christopher and CJ escape in the mothership makes Venter incredibly angry, so he shoots
the suit until he destroys it.
Wikus crawls out of it, showing his left eye is swollen and yellow, meaning he's about
to finish transforming.
Venter points his gun at him ready to kill, but suddenly a bunch of prawns show up and
kill him first to save Wikus, who is now seen as a prawn too.
Sometime later, humans celebrate that the mothership has left Earth.
Wikus' assistant exposes the MNU's illegal research, and the government safely transfers
all the 2.5 million prawns to the new District 10 before demolishing 9.
Wikus' story become infamous, but most people stop thinking about him after a while, thinking
he's dead.
However Tania is sure Wikus is fine because she's found a handcrafted metal flower at
her door, and Wikus has always liked crafts.
Back in the landfill, it's revealed Wikus is alive and fully a prawn now, and he makes
more metal flowers with trash.