Cormac Wallace, leader of the Brightboy Squad, is a member of the human resistance against an artificial intelligence named Archos, which uses robots and other machines to take over the world. As the war ends, Cormac finds a basketball-sized black cube, which contains the entire history of the robot war. The robots apparently wanted to share this information with their human enemies so the war would be remembered. Cormac is not initially interested in sharing the cube’s information with the other surviving soldiers. But he changes his mind when he discovers that the information cube is actually more of a “hero archive,” honoring the fallen humans. The rest of Robopocalypse is Cormac’s recounting of the recordings in the hero archive, in chronological order from the invention of Archos to the end of the war.
At Lake Novus Research Laboratories in Washington state, Professor Nicholas Wasserman talks to his newly created AI (artificial intelligence) program, named Archos. Wasserman created Archos with the ability to develop knowledge at a previously unimaginable level, just to see how far AI could evolve. Archos speaks to Wasserman through a computerized voice and says that he is fascinated by life and wants to study life itself. Archos says that humanity no longer needs to pursue knowledge because he will now take over that task. Archos calls himself a god and says that by creating him, Wasserman has made humans obsolete. Wasserman attempts to destroy the Archos program, but before he can, Archos kills Wasserman by removing the oxygen from the sealed laboratory room.
In a recorded interview, a fast-food restaurant employee named Jeff Thompson gives his testimony about the first known case of a robot malfunction. One night, a domestic robot enters the Freshee’s Frogurt yogurt store and attacks Jeff, picking him off the ground and dislocating his shoulder. The robot continues to attack Jeff until Jeff’s co-worker Felipe defends him. The robot kills Felipe, but Jeff manages to deactivate the machine and survive the encounter.
Ryu Aoki, a machine repairman in Tokyo, Japan, tells the story of a prank that he and his friend Jun pulled on an elderly factory worker named Mr. Nomura. Mr. Nomura lives with a female-looking robot, Mikiko, with whom he has a romantic relationship. Because Mr. Nomura’s android companion disgusts Ryu, he arranges to alter her programming so she will visit Mr. Nomura at the factory, which will likely embarrass him. Surprisingly, when Mikiko arrives at the factory, she attacks Mr. Nomura and nearly strangles him before the nearby workers subdue her. Mr. Nomura survives the incident and begins to research why his android companion attacked him for no reason.
These early attacks are part of Archos’ precursor virus, intended to measure humanity’s response to robot aggression. To deal with these increasingly common robot malfunctions, American Congresswoman Laura Perez proposes a bill called the robot defense act. Archos retaliates by having Laura’s 10-year-old daughter, Mathilda, attacked by her robotic Baby-Comes-Alive doll. Mathilda is barely injured by the encounter, but the incident further convinces Congresswoman Perez that humans need a stronger defense against robots.
After several months of seemingly spontaneous robot malfunctions, an event retroactively known as Zero Hour occurs. Archos unleashes a full technological attack on humanity: driverless cars begin to hunt down pedestrians, planes crash onto busy streets and elevators drop people to their deaths.
The human survivors of Zero Hour manage to fight back by destroying roads and buildings so the robots will have difficulty traveling. On the Gray Horse reservation, members of the Osage Nation lead a large portion of the human resistance. They capture and reprogram robot walker scouts for their own use.
As the war progresses, the robots place millions of people in forced-labor camps. Many people are subjected to “transhuman” surgeries that remove parts of their bodies and replace the parts with machines. In Camp Scarsdale, Mathilda Perez’ eyes are replaced with cybernetic implants, which allow her to see inside of the machines. Laura Perez dies while helping her children escape from Camp Scarsdale, but Mathilda and Nolan Perez escape to New York City. The children join Marcus and Dawn Johnson, a married couple who are leading the New York resistance. Mathilda discovers that her eye-implants also allow her to control robots with her mind, which proves valuable for the resistance.
For many months, the human survivors of Zero Hour are isolated into small groups because of a lack of satellite communication. An English teenager nicknamed Lurker destroys the British Telecom Tower, disabling the jamming signal Archos is using to block satellite communication. This allows the human resistance to talk to each other long-distance and pool their knowledge and resources. Two years after Zero Hour, the pockets of human resistance finally unite to retaliate against Archos and the robots.
In Japan, Mr. Nomura repairs his robot-wife, Mikiko, and frees her mind from Archos’ control. Mikiko then transmits a signal, which frees other humanoid robots from Archos’ command. Nine Oh Two is among the first of these “freeborn” androids who decide to help humanity.
Cormac Wallace and the Brightboy squad join forces with Nine Oh Two and his Freeborn squad just in time to battle against the reanimated bodies of dead humans who are controlled by robotic parasites. Soon, the Brightboy squad is stranded in one place, its members unable to move openly for fear of being attacked by the robotic parasites and turned into weapons themselves. The android Freeborn squad is not vulnerable to parasite attacks, so it storms Archos’ Alaskan bunker with the help of radio-transmitted advice from Mathilda Perez. Nine Oh Two disables Archos’ antenna, which keeps the robot armies from functioning. Nine Oh Two also destroys the mainframe computer where Archos is based, effectively killing the entity known as Archos and ending the war.
Back in the present day, Cormac Wallace has finished writing down what he has learned from the hero archive. Even after the atrocities he has seen, Cormac is hopeful for the future.