Meanwhile, on Mars, Armitage puts the finishing touches on a cake she just baked. A commercial on a monitor in her kitchen describes a plan to provide Mars with water by melting large chunks of frozen ice from space onto the planet’s equator.
In direct contrast to this peaceful scene is the attack going on on Earth. Lab technicians are gunned down mercilessly by the battle-armoured soldiers as a computer issues a warning about the overload of the anti-matter reactor. As the soldiers press on, a woman looks up at them and she appears to be- Armitage? Colonel Strings steps forward, proclaiming that what he does is for the sake of humanity, and executes the mystery woman. Behind her body are a number of large tubes, each containing a comatose woman who also looks just like Armitage. The eyes of the fallen woman flash red, and on Mars Armitage drops the pot she was holding and gasps as the facility on Earth is destroyed by the explosion of its reactor.
Recovering from her shock, Armitage realizes that she has just been contacted by another Third, just as Jessica Manning contacted her directly years before. On her monitor, a newswoman announces that special forces troops have been sent to an anti-matter plant on Earth where robots have rebelled and killed many staff members. Armitage, however, knows the truth.
In another part of St. Lowell Ross pulls up in front of a kindergarten, and is met by Yoko- he and Armitage’s daughter. They return home to a beautiful terraced neighbourhood, and as they enter the news program on the monitor shows a statement by President Heming of the Earth Robotronics Union that the problems encountered with the robots of the anti-matter plant is isolated to Second-types manufactured on Mars, and that Earth-produced Seconds have an obedience circuit that prevents such things. Armitage then enters from the kitchen, revealing the reason for the cake- Yoko’s birthday. Around the table later, as Yoko blows out her candles, Ross gives Armitage flowers, and a confused Yoko asks if it is her birthday too, prompting Armitage to consider her own birthday--or lack thereof.
That evening, with Ross and Yoko safely asleep, Armitage dresses in her old gear and leaves the house, putting on a pair of shades as she does- a sure sign that she means business. She travels to Earth, arriving in Chicago and finding it just as intolerant of robots as she had heard--a newscaster reports that the police are considering reducing the number of robots used for simple tasks in the department. As Armitage rides the train she sees an interview with Colonel Strings on a public monitor, giving details about the anti-matter facility raid, now known as the First Error--details Armitage knows don’t tell the whole story. The Colonel ends his interview that the proclamation that human rights are reserved for humans, and not machines.
Later, Armitage waits in the shadows outside the news building as a limo pulls up and two bodyguards get out. Colonel Strings walks from the building and gets in the car, and Armitage follows, saving the limo’s license plate number to her memory. As the limo tries to lose her, Armitage is forced to override its robotic driver with a swift punch and take off after it, weaving through traffic. The limo eventually pulls into a deserted area and stops. As Armitage approaches, she checks the plate against her memory and it matches- this seems to be the car she followed. The two bodyguards emerge from the limo, demanding to know who Armitage is and brandishing guns, and they open fire when she questions them back.
Weaving and dodging to avoid the bullets, Armitage quickly disposes of the two guards, and when she does a laser sight from inside the limo settles on her chest. A quick leap onto the limo takes her out of sight, and another quick leap lets her escape the hail of bullets that are fired through the roof from inside the car. From the ruined car emerges a man in battle-armour- not Colonel Strings, but someone else who mistakes Armitage for a Second-type with advanced hand-to-hand combat training. The first punch the mystery man lands convinces Armitage of the dangers of underestimating him- he knocks her tumbling and wheezing against a wall. He sights in on her again with the laser sight and fires a long burst, then advances, fully expecting his prey to be dead. This is his last mistake as Armitage beats him badly with a length of metal pipe and then lifts him into the air, tossing him down again on his head. Opening her downed opponent’s suit, she finds he is a Sergeant in Earth’s military under the command of Colonel Strings. Retrieving a pistol from a downed man, she notices a countdown going on inside the limo and runs, barely escaping its explosion, an explosion that destroys the evidence of the trap. In his office, a mysterious man watches a tape of the encounter, delighted to see that the “lost Third” is still alive.
On Mars, Ross reports for work as a security guard in his new identity as Kevin Oldman. He relieves another guard and learns of a death threat against the plant he guards, which makes high-impulse propellant. As Ross goes about his rounds, he hears gunfire. When he tries to trip the alarm, it doesn’t work, so he keeps moving and encounters a group of masked terrorists. Pinned down by gunfire, Ross fires back when he can, and takes his chance when he sees it- during in a lull in the firing he moves to a pull-switch and throws it, bringing a heavy armoured door down to close off the corridor. One of the terrorists pulls out a grenade and Ross shoots him. The activated grenade bounces off the floor just as the door seals shut, and the explosion on the other side of the door kills all terrorists in the area.
Later, as the police investigate, Ross is congratulated by his boss but warned that the fact that only human terrorists were killed and their robot partners were captured alive will be played on by the media. At the same time on Earth, Armitage sits in a coffee bar and makes contact with Julian through her shades. After a bit of teasing, he gives her what she asks for- information about the First Error. As she leaves the coffee house, an image of Ross at press conference following the attack shows on a public screen. As expected, the press tries to make it look like Ross killed the humans and let the robots escape because he is a robot-lover, and he doesn’t help matters with an outburst stating that robots only do what they are told and that it is humans who are the offenders.
In an office, yet another mysterious man watches the program, and a newscaster explains that Ross has gained popularity with robots-rights supporters due to his statements. She goes on to explain that the Chicago Summit between Earth and Mars will soon address the subject of a Robot Rights Bill and that the incident at Ross’ workplace will have a major effect on the outcome of the voting. Her statements are supported by analyst Richard Mischook, who explains that the question under consideration is whether robots should be granted some of the same rights as humans. Earth has, in the main, opposed the idea, while more liberal Mars has supported it. The deadlock faltered after the First Error, when Mars began to change its mind, but the boost given to robots-rights movements by the terrorist attack has evened things out again. After the broadcast, the stranger looks bemused and says, “You really did it this time, Kevin-- or, should I say Ross Sylibus?”
Back on Earth, Armitage enters a hotel where evidence of anti-robot sentiment rears its head again- all of the robot doormen have been let go. Irritated, Armitage gets in an elevator and withdraws a heavy pistol from the instrument case she carries. Arriving at her destination, she enters a hotel room and confronts Colonel Strings, who has no idea who she is. As Armitage berates him, looking for answers, Strings states that she acts as if she was there during the assault, and the way in which she responds is uniquely Armitage: in his own voice, she replays Strings’ sentence of death to the robots in the plant to him. She then pins him to his desk and puts her gun to his forehead, claiming that he slaughtered everyone simply to cover the existence of the Third project. A very confused Strings asks what the Third project is, and an angry Armitage prepares to shoot him.
The entrance of three men interrupts the execution, including the mysterious man who recognized Armitage as the lost Third, is known to Strings--a man named Demitrio. Rather than have the hero of the First Error killed by a robot, Demitrio has his men kill Strings. Demitrio then introduces himself to Armitage, explaining that he is the executive Vice-president of Earth Robotronics and that he knows who she really is as well.
Meanwhile, on Mars, Ross meets the other mysterious man who knew his identity, and seems pleased to see him. He is Frederick O’Hara, Chairman of the Martian Development Foundation, and he asks Ross to go in his place to the Chicago Summit. Ross has become someone the robots-rights groups will rally around, and the Chairman wishes to take advantage of that, as he knows Ross will vote the same way he would- yes for robotic rights.
Armitage’s meeting with her mystery man is less pleasant, as he explains that the demand for Seconds produced on Mars is slowing down business for his company and that things will only get worse if the Robot Rights Bill passes. He manipulated Strings to produce the First Error attack to swing votes his way, though he and Armitage both know that there was a bit more to it than that. There was in fact a robotic rebellion, as the Thirds kept in the anti-matter plant tried to escape- a real rebellion behind the false one. After explaining his plan, Demitrio gives Armitage the opportunity to come with him and help, which she of course refuses.
Demitrio’s response is simply step aside as a large robot crashes through the wall and is ordered to grab Armitage. Her vision fills with static as the robot activates specialized ECM (Electronic Counter Measures). Knocked around, nearly shot, and then punctured by several large flechettes, Armitage seems helpless- until she stops the robot in its tracks with her glowing red eyes. One touch to its gun arm creates an explosion that fills the hotel room, and when Demitrio recovers, Armitage is gone.
While she is unconscious in the sewer beneath Chicago, Armitage is found by a scrounger and taken to a small repair shop. There, the crazily-giggling Mouse inspects her. As he accesses her recent memories, Armitage awakens and forces him out of her mind. For a large payment of earth dollars, Mouse agrees to repair her badly-damaged body.
Ten days later, a passenger ship arrives from Mars carrying Ross and Yoko, on their way to the Chicago Summit. Ross remembers his conversation with the Chairman, where he learns that Earth is threatened by recent calls for Martian independence. These independence movements are gaining supporters due to the possibility of giving Mars more water via space icebergs and the popularity of Martian robots. If the Robot Rights Bill passes, the only reason Earth robots are purchased- their obedience circuit- will be made illegal and Earth will have to depend even more on Mars. As Mars is a valuable colony for Earth, they have no intention of losing it, and the Robot Rights Bill is much more important politically than it seems. This, then, is why the Chairman sent Ross- he needs to use every advantage he has to ensure the passing of the bill.
Once he arrives on Earth, Ross is watched by Demitrio as he goes about his business. A news announcement reveals that stock in Earth Robotronics has risen due to the announcement that all new robots produced by them will have a slave circuit making them incapable of harming humans. It is expected that the sagging robotics industry of Earth will get a serious boost if the Robot Rights Bill fails to pass. Later, Ross meets with Demitrio and learns that he has taken Yoko hostage. His condition for her safe release is that Ross vote against the Robot Rights Bill.
On the day of the Chicago Summit, Armitage is up and around once again, and sees a live broadcast of the vote on the Robot Rights Bill. She is surprised and confused to see Ross there as a voting member, and even more surprised when he is the only Martian who doesn’t vote yes. Unable to abandon his daughter but also unwilling to completely abandon his values and beliefs, Ross instead chooses to abstain, voting neither yes nor no. This is not much of a compromise, however, as Ross’ abstention is the only reason the Bill fails to pass.
Meanwhile, in a lab Demitrio approaches two Armitage look-alikes lying on metal beds. Scanning through their files he wonders what he is missing- why can’t he figure out how to allow his robots to reproduce? As he does so, a message arrives in the shape of a cutesy Armitage blowing hearts and asking if he wants her data. When Demitrio says yes, the message agrees to transfer some sample data and suggests he contact Mouse Robot Service if he wants more. Seems Mouse made a copy of Armitage’s files. He does so and meets with Mouse, then becomes enraged when he sees that the information on reproduction is missing. When Mouse explains that he simply doesn’t have that data, Demitrio first refuses to believe him. Then, as punishment, Demitrio unleashes his two Armitage copies on Mouse, and reveals that the only difference between them and Armitage is the ability to reproduce. Mouse is then badly beaten and his memory bank accessed- apparently, Mouse is a robot too. When the information Demitrio wants isn’t found, he has Mouse’s broken body thrown into the trash where Mouse swears revenge before passing out.
On a rooftop somewhere in Chicago, Armitage contacts Ross’ hotel and tries to get in touch with him, but he hasn’t returned there since the Chicago Summit. Ross, on the other hand, is meeting with Demitrio’s men to get Yoko back. Instead of giving him his daughter, however, they open fire on Ross. He dodges away and escapes by stealing a car from a couple making out nearby, though the thugs are quick to give chase. A high-speed chase on the streets of Chicago ensues, complete with gunfire and amazing leaps over separating bridges. After losing the thugs, a helicopter gunship attacks Ross, destroying his stolen car. As it prepares to kill him, someone shoots out one of the gunship’s spotlights- Armitage has found her husband. The gunship chooses to go after her then, firing a volley of rockets that she leaps over, landing on the cockpit of the chopper. The pilots panic and crash the machine into a building, and Armitage meets up with Ross below.
Away from the attack, Ross explains what has happened to Yoko, and Armitage apologizes for leaving without telling him. Ross tells her to stop taking on every problem by herself- that they are a family. The two of them decide to try to rescue Yoko together, and the march of two extremely pissed-off and protective parents begins.
Their first stop is, of course, the Earth Robotronics building. Two guard robots watch as Armitage walks slowly up to them, despite their warnings about her unverified identification and the use of force. As they prepare to fire, Armitage identifies herself and leaps over their heads and through a window to gain entry. Inside the lobby of the building are rows of more guard robots, which open fire on her. Running deeper into the building and firing her pistol as she goes, Armitage takes several of the guards down, gaining entry into the elevator and heading up.
Inside the elevator, she reloads her weapon, then looks up at a security camera and delivers a chilling message to Demitrio: “If you’ve harmed a hair on my daughter, I’m going to kill you.” Then she shoots the camera. Demitrio, waiting in his office, gets the message and is unimpressed.
Ross, meanwhile, is in another part of the building and moving up the stairs. His encounter with a guard robot ends the same way as Armitage’s did- a dead robot. As he fights, Armitage accesses the building’s computer for a map, locating both Demitrio and Yoko. She contacts Ross via a radio receiver and tells him where their daughter is. Ross, for his part, has contacted Mars and has a shuttle waiting scheduled to take off at five A.M., giving them four hours to rescue Yoko and take care of Demitrio.
During the conversation, security walls have come down in several parts of the building, blocking access. This is no problem for Armitage, who simply shoulder blocks her way through. Her next problem is more dangerous- another of the large robots Demitrio had tried to kidnap her with in Colonel Strings’ hotel room. She is about to take care of this one just as she did the other when Demitrio appears on a screen in the wall and asks her not to destroy any more of his merchandise. He then requests that they resume their previous discussion about Armitage helping him and when she refuses, he shows her footage of Yoko- huddled up for warmth, her breath freezing in the air as she exhales. Attempting to release Yoko remotely through the building’s computer, Armitage finds that Demitrio has had the access protected and she can’t get in.
Ross has finally found the room Armitage sent him to, and finds the door electronically locked. He asks Armitage for help, but she can’t get past the protection. She also tells him that Yoko is freezing to death inside, and that she’ll buy some time while Ross rescues their daughter. As Ross tries desperately to open the lock, Armitage surrenders to Demitrio. A frustrated Ross shoots out the lock’s control panel, then grabs hold with both hands and begins a desperate attempt to pull the door open using only his cybernetically-enhanced body.
Armitage, meanwhile, has been brought before Demitrio by his giant robot. He reveals that his tests show Yoko to have no unusual abilities, just a normal human child. That means Armitage is his last hope for discovering the secret of the Thirds- the ability to conceive. He offers to forget all past damages if she will give him the secret, and she draws him close to her, then kicks him in the crotch. Demitrio stops his bodyguards from retaliating, aware that if he kills Armitage her secret will be lost. Armitage reveals that Demitrio has been looking in the wrong place for the secret. It isn’t just in the physical body- it is in the heart, in the need of a mother to pass her love on to the future. At the same time, after incredible straining, Ross has finally torn open the door and rescued Yoko from the freezer.
Breaking free from Demitrio’s giant robot, Armitage leaves the confused kidnapper behind her, running down the halls to help her family. Demitrio activates the two copies of Armitage and sends them after her, and they quickly catch up due to small wheels on their feet that act as in-line skates. The pair surprise Armitage with their abilities, cutting her shoulder open, and surprise her again when she realizes that they are replicas of her. Their fight carries them through a wall and into the corridor where Ross and Yoko wait. Yoko runs to her mother, only to back away when she sees Armitage’s shoulder- she was unaware that her mother is a robot, and that knowledge stuns the little girl. A hurt Armitage can only watch as her daughter rejects her.
Behind Ross and Yoko the elevator door opens, and they get inside while Armitage turns to deal with the approaching pair of copies. As Ross and Yoko speed away, Armitage is knocked through a window and out of the building, grabbing hold of a ledge to save herself from a long drop. The copies continue to tear at her relentlessly and Armitage realizes that she cannot defeat them, so she leaps from the building onto a truck on the street far below. Her only hope now is Mouse, who is still busy repairing himself after his near-fatal encounter with Demitrio.
Ross and Yoko arrive at the Orbital Booster Tower and find it abandoned. They are forced to hop the turnstiles and then enter an elevator, heading for their ship. Arriving at the tower close behind them are the copies. When Ross discovers that the elevator he has chosen doesn’t go all the way to their shuttle, Yoko points out an elevator to him, explaining that her knowledge of the area is a secret and he has to trust her. Ross does, and calls it, only to be attacked by one of the copies as they wait. Ross is warned by Yoko and is able to stop the attack, taking a knife through his hand but saving his life. When the elevator door opens, Ross kicks the copy away and he and Yoko get on, shutting out their attacker.
They soon discover that the other copy is attached to the bottom of the elevator, and it comes bursting through the floor and kicks Ross’ gun out of his hand. With little room to manoeuvre, Ross is in trouble, and Yoko runs up to the copy and grabs it in a futile attempt to stop it. The copy raises its blade to kill her, and Armitage bolts upright on her table in Mouse’s workshop, aware somehow that her daughter is in danger. She tells Mouse to release her Combat Mode Limiter, which keeps her combat performance at a level that her body structure can withstand. Without those limits, her body will overheat and tear itself apart when she fights, but she will be significantly more effective in combat for the short time that she lives. Mouse agrees unhappily, and sets the password for the Limiter release as ‘Heaven’s Door’.
The elevator door opens at the level for their shuttle and Ross is tossed out by the copy, who has left Yoko unharmed. Again, Yoko gives Ross directions, and they get on a lift. There, Yoko reveals that she memorized the entire floorplan of the tower when she looked at a map at the entrance, and then draws it for Ross. Looking over the side as Yoko draws, Ross sees both copies speeding up towards him, up the side of the tower. They leap up onto the lift, and one attacks Ross while the other walks slowly toward Yoko, giggling slightly. As it reaches for Yoko, a gun fires- Armitage has returned.
As the copies turn to face this new threat, Armitage tosses aside her shades and prepares to fight. Ross and Yoko get on yet another lift and head for the shuttle, leaving Armitage behind once again to guard their retreat. Meanwhile, Mouse, at Armitage’s request, has taken control of public screens and begun broadcasting the memories of a Third copy and what really went on during the First Error. He implicates Demitrio in the affair, publicly ruining him.
Back in the tower, the copies receives orders from Demitrio- they are not to let any of the family leave the Earth. A fierce battle ensues, as the two copies do their best to kill Armitage, and she is badly hurt and knocked over the side of the tower. Believing her dead, the copies move on to Ross and Yoko, releasing the lift they are on to fall to the ground. Ross leaps for a ladder with Yoko in his hand and barely escapes, then begins the laborious climb up. One of the copies goes down to finish them off, but Armitage re-enters the fray, using one copy as a springboard to get to the other, which she tosses over the side.
Again, Ross and Yoko run while Armitage guards them, the very image of the fierce protective mother. Up and down the side of the tower the robots fight, as Ross struggles to climb as fast as he can. Finally, he makes it to the top, and he and Yoko approach the final elevator that will take them directly to their shuttle. Ross hears a noise and turns, to find Armitage there badly beaten but alive. Exhausted, she slumps to the ground, but a still-wary Yoko refuses to run to her.
After exiting the elevator, the trio see their shuttle and Ross goes ahead to look around. Armitage tries once more to embrace her child, but a new wound has scared Yoko again and she refuses, leaving her mother heartsick. Ross returns just as another elevator opens, and as they wait to see who will emerge one of the copies bursts through the floor beneath Armitage and attacks. It then tosses Ross aside and grabs Yoko by the throat, but releases her and turns to face Armitage. The robot easily overcomes Armitage’s defences, grabbing her and savagely slamming her head into a wall over and over again. Finally, it releases Armitage and produces a blade, ready for the kill. The next thing it hears however, is the phrase ‘Heaven’s Door’.
With Armitage’s Limiter released, she begins moving with a speed and strength several times greater than even her normal superior levels. The copy doesn’t stand a chance, and Armitage literally squeezes one arm with her hand until the lower part falls off in a spray of blood and wires. Grabbing the copy’s face, she then reads its programming, then punches it in the face so hard that chips of metal fly and the copy is knocked into an elevator. Her skin burning away from the extra heat her actions have produced, Armitage then falls to her knees, having reached her limit. The copy is not dead, however, and pries itself out of the dented wall it was trapped in and heads for Armitage. Finally, Yoko overcomes her fears and runs to her mother, jumping on her back and embracing her, begging her to stop fighting as she is hurt quite badly.
A protective Ross attacks the oncoming copy with a pipe, and is able to knock it back into the elevator and send it down. Finally, the family is safe, and they board their shuttle. Or are they safe? Demitrio has not forgotten about them, and he enters the tower’s main control room. Using the fact that the shuttle isn’t registered, he prepares to open fire on it with the tower’s defences. Before he can do so, he turns to see the copy Ross sent down the elevator standing behind him. As he stares at it uncomprehendingly, the copy plunges its blade into his chest, then speaks with Armitage’s voice: “I told you- I said if you harmed a hair on my daughter I would kill you.” As Demitrio dies, the copy slumps over on top of him, and Julian’s ghostly form materializes from inside of it. He bids his sister’s shuttle ‘So long’, and disappears.
On Earth it is announced that the plan to give Mars water by using space icebergs has passed. This is followed by the idyllic image of Ross and Armitage playing at the beach on Mars with Yoko. The final image of the film, however, occurs after the credits, as Mouse is shown repairing the damaged copy of Armitage to be his servant.