It has been 70 years since the inception of terra-forming on Mars, the fourth planet in the solar system. Many robots are needed for the work of terra-forming, consequently the robot industry on Mars increased tremendously. Currently, this industry is the primary commodity of exchange with Earth. However, in reality, Mars is not independent form Earth; they must still depend on Earth for politics and culture.
A man arrives at the St. Lowel spaceport on Mars. His name is Ross Sylibus, a detective who has been transferred from Earth to the Martian Police Department. However, Ross becomes involved in a murder when detective Armitage from the MPD picks him up. The victim is Kelly McCannon, a country singer of Mars. Ross sees an indicator light flashing from behind the bullet wound. Kelly was not a human, she must have been a robot! A robot of the "Second" type currently used on Mars is different; Kelly doesn't have an on/off switch on her temple. She is indistinguishable form a human. The megastar singer is the latest type of robot. Everyone on Mars is shocked. In the meantime the MPD has discovered as a result of the autopsy that Kelly was more advanced than the "Second" type. She was not a cyborg, but a robot with creative abilities; a true neo-human. Is she a "Third"?
Investigating the incident with Ross is Armitage, the person who came to pick him up at the spaceport. The two begin their search for evidence. Ross has second thoughts about his involvement in the robot murder since he lost his girlfriend to a robot criminal. Armitage dislikes Ross for feeling this way. Ross sees there is a sensitive spot in her heart, and that she is hiding something behind her strong words. Rene D'anclaude confesses to the murder of Kelly McCannon via video mail to the media. The "Thirds", so incredibly similar to humans, must go into hiding. The "Thirds" represent a threat to people's lives. D'anclaude finds the "Thirds" one by one, and destroys them. D'anclaude's voice rings from the video mail. "And I found another one — this is Jessica Manning! She is just a robot! What do you think about that? Ha! ha! So what are you going to do? Ha, ha, ha!" Armitage who had received a letter from Jessica requesting protection, leaves Ross to begin her own investigation. However, Jessica is destroyed by citizens opposed to the robots. Meanwhile, Ross discoveres where D'anclaude is hiding and steps into a church that is under construction. Ross chases D'anclaude.
"Ha, ha! I'm just exterminating illegal robots!" says D'anclaude.
When Ross is backed into a corner he is saved by Armitage. She comes close to capturing D'anclaude by doing things no human can do.
"D'anclaude! Let me tell you why I can't forgive you. Why am I an ally to the robots? Why I believe in the existence of the Third? I'll tell you, it's because…!"
In a freight elevator of an industrial power plant, a bullet-riddled body is discovered. The victim's name? Lavinia Whately. Her profession? Entertainer. According to certain components later identified within her body, the victim was one of an advanced series of androids called "Thirds", whose mere existence is kept secret from the public.
The suspect, a man named D'anclaude, is eventually apprehended by Armitage and held for questioning at the police medical facility. Details of the crime are scarce, baffling the members of the Martian Police Department.
But this "Third" murder isn't the only thing on MPD Officer Ross Sylibus' mind. Armitage, his partner, disappeared shortly after the start of the investigation, and her whereabouts are still unknown. Between cases, Ross tries to track her down by paying visits to both her apartment and the high-tech android manufacturing fim Conception, but is unable to come up with any leads. And then there's another death.
Rosalind Holhess (Jorgez? -ed.), a novelist, is found murdered in her home. Sometime before she was killed the name "Armitage" was entered into her word processor leading police ot believe that Ross' partner is somehow involved in the crime. An APB is issued for Armitage listing her as under suspicion of murder.
Upon inspection of Rosalind's electronic mail log, Ross idscovers a mention of a message sent by an individual using the handle "Pluto". When he discovers that the message was sent using Armitage's own e-mail address, Ross realizes that he's just found his first lead in the case. While hurrying to the original transmission source of the e-mail message, the MPD busies itself analyzing the message itself, eventually discovering a data file with the names of all "Thirds" currently known to exist.
As it turns out, each "Third" has been assigned a codename corresponding to a planet in the Solar System. Aside from "Earth" (Armitage), the only codename left unaccounted for is "Pluto". This has to be the next target!
En route to the transmission point, Ross recieves a message regarding Lavinia Whately's autopsy. Lavinia, it seems, was pregnant. An android capable of giving birth! Ross gains a valuable new insight into the hidden nature of the "Thirds".
Ross arrives at his destination, a downtown elementary school. Armitage, who's been waiting for him, explains that she was acting on her own to protect "Pluto" from the anticipated assassination attempt. As her partner, Ross decides to join forces with her and heads into the school building.
While a surprise discovery reveals "Pluto" to be a young boy named Julian, the assassin draws nearer to the intended target. When the three — Ross, Armitage, and Julian — are cornered by the assassin in an underground power plant, will the identity of the assassin be revealed at last?
Before the shock of the current wave of "Third" murders can subside, a rash of indiscriminate terrorist bombings plague the citizens of Mars. As it turns out, the bombings have been committed with the help of the androids known as "Seconds", who are implanted with bombs and set out on their deadly missions by some unknown agency. Even though it means that they'll be taken off the "Third" investigation, the decision is made to place the MPD (Martian Police Department) in charge of the bombing investigation.
MPD Detective Ross Sylibus, now with 47% of his body replaced by artificial organs because of the previous battle with D'anclaude, is faced with a hard decision: Follow orders and pursue the "Second" bombings, or follow his conscience and continue the "Third" investigation on his own. Ross chooses the latter.
Leads on the "Third" case are scarce, however. "D'anclaude is definitely in custody," says Shinora Police Hospital in response to Ross' inquiries, but they're decidedly reluctant to diculge further details. Just as he prepares to leave the hospital, Ross catches sight of Eugene Allen, Vice-President of Conception Corporation. Something, Ross decides, is definitely rotten in St. Lowell City.
Meanwhile, Armitage hears a shocking truth from Julian:
Thirds are robots capable of becoming pregnant.
W-Why were such robots made!?
Unfortunately, the only ones capable of answering Armitage's question are Asakura and D'anclaude — and they're not exactly available for questioning at moment. In order to obtain more information regarding Asakura, Armitage and Julian infiltrate the IO Memory Bank at Ad Tower. Julian accesses a terminal and discovers a very peculiar video still-image, showing a several-years-old photo of Asakura, standing shoulder-to-shoulder with D'anclaude. What can it mean?
As Armitage tires to fathom the meaning of the photo, she's suddenly attacked… by Julian! It turns out that during an earlier distraction, D'anclaude managed to obtain remote-access to Julian's body without Armitage's knowledge.
It's useless for you to investigate further, because each and every Third is GOING TO DIE—!
Using Julian as his tool, D'anclaude makes things very, very difficult for Armitage. Eventually, she's able to destroy the circuit-board and thereby terminate D'anclaude's remote-control access, but the cost is Julian's life.
Elsewhere, while Armitage fights for her life, Ross catches Mr. Allen using an illegal application red-handed, and forces him to divulge the secret of Shinora.
Rene D'anclaude… the insider at Shinora is Dr. Rene D'anclaude… the same person who created the 'Assassinroid.'
Ross soon realizes the full horror of Mr. Allen's revelation: D'anclaude is an "Assasinroid" made in Dr. Rene D'anclaude's image. D'anclaude, it seems, is a "Third" himself.
Later, Ross and Armitage rendezvous. Armitage tells Ross of Julian's tragic death while she mourns the loss of her friend. But she can't mourn for long, as Ross has an important reminder: Julian's memory is backed-up at Ad Tower, and the information Armitage and Ross need may still be available if they hurry.
Armitage and Ross race into cyberspace and access the tower's program. Julian is there… as well as the other "Thirds," who still exist in data-form.
I don't know where Asakura is… but D'anclaude is at Shinora.
Armed in full-combat gear, Armitage and Ross head toward Shinora. Their goal? To find/capture/talk to the person who's at the center of it all, Dr. Rene D'anclaude himself! But Armitage and Ross won't be arriving unannounced, as military security gadgets and armed "Seconds" are there to welcome them. By taking advantage of her special "Third" skills and with Ross' help, Armitage MAY have a chance of surviving what has now become a battlefield. As for whether or not she lives to tell the tale… you'll have to wait until next time to find out!
During the battle between D'anclaude and Armitage, Shinora is engulfed in flames. Although Armitage manages to escape with Ross, the two D'anclaudes — the original, and the Third — are lost in the fire, but not before giving the two MPD detectives a vital clue: "Asakura is at the dome on top of Dannich Hill." Knowing Asakura is now the only one who can reveal the secret behind the development of the Thirds, Armitage and Ross set out for Dannich Hill. Even without the lead, they would have had to meet Asakura; Armitage's logic board was damaged during the battle at Shinora, and it must be repaired.
When Armitage and Ross arrive at the dome, they discover it to be filled with a dense array of trees, arranged almost as though the dome were a botanical garden. Plant-based bioroids and a small woodland creature never seen before lead Armitage and Ross to conclude that the dome is a former test site for the Martian terraforming project.
While the two search for Asakura, Armitage and Ross are confronted once more… by none other than D'anclaude! Eventually, it's discovered that their would-be attacker is named "Wilbur" and only looks like D'anclaude. It turns out he's the robot assistant of Asakura. Wilbur leads Armitage and Ross to Asakura, who oddly shows no reaction to or recognition of his "daughter." Armitage, of course, is at a loss. It seems Asakura has been psychologically altered, and is now living the life of hermit in the dome, researching a new bioroid called "ALIVE."
That night, suffering from the shock of seeing her "father" so changed, Armitage opens up to Ross. "Now I'll never find out what I really am, or why I was created," she says. "Or why the Thirds had to die… I don't have any more reasons for staying alive."
Ross comforts the distraught Armitage. "But for now, you are alive, and no one can take away your right to live…" Armitage and Ross embrace, their hearts together as one.
The next morning, led once again by Wilbur, Armitage and Ross are taken to see an incomplete bioroid which bears an uncanny resemblance to Armitage.
"She was to have become your sister…"
Thanks to Wilbur's words, the secret of Dr. Asakura and D'anclaude's research has at last been revealed.