Casey McKenna along with her husband Peter McKenna, and Mr. Taggart founded the Aquarius Corporation, and set up a complex in New York City. She is the chief of security at Aquarius. The primary focus of the Aquarius Corporation is biocircuitry. They also have a a telepathic quadriplegic named Billy Challas.
While giving a tour of the complex, Casey is interrupted by a demon named Agat, who had broken through the security defenses, and attempted to kill Billy Challas . Virgo intervened and caused an explosion that expelled both Billy- who had been turned into the ronin, and Agat. Casey is urged by Virgo to go out and find the ronin, but she skeptical as to why. Virgo explains to Casey that she had to create the explosion to save Billy Challas, but Casey believes that Virgo’s logic units are malfunctioning. Casey Eventually begins an investigation into the Ronin as a part of her report, and sets out to find him.
Casey gathers up her men to go into the city and find the ronin, but when three of her men eventually locate the ronin, they are all murdered. Casey is shown the surveillance of what happened and is finally convinced that Virgo’s story is true. Casey requests to go back out to capture the ronin, and kill him. Mr. Taggart gives Casey only tasers, and instructs her to bring him back alive. Casey is unaware that Mr. Taggart has been killed and Agat has taken over his body.
Virgo reveals to Casey that she knows where the ronin is, but is worried that Casey may try to avenge her fallen comrades, if she tells where he is, but Casey reassures Virgo of her orders. While on the chase for the ronin, Virgo scans Casey, and discovers that she has a magnum on her hip. Casey finally tracks the ronin down, and fires her gun at him. The ronin returns fire, but with arrows and shoots down most of her men, before they are finally able to tase him. It doesn’t last long as he blows up their weapons. Still very much injured the Ronin almost gets blown away by Casey, until she is knocked unconscious by two rival factions and thrown into a deep pit, where cannibals live. She eventually is rescued by the ronin, who moments before, she tried to kill. Strangely, Casey finds herself falling in love with the ronin and even sleeps with him, but she can’t explain why.
Casey along with the ronin have been mysteriously thrown into feudal Japan, and head for the Aquarius complex on horse. Before they can reach their destination they are stopped by Agat’s slaves. The ronin defeats most of them, but a few try to take Casey has a hostage. Armed with only a sword Casey dispatches them, and is surprised that she can wield a sword. The ronin claims that she is in fact a samurai. Without warning the ronin’s right arm is shot off, and they are once back in the twenty-first century.
Agat’s slaves are nothing more than robots, powered by Virgo. The Ronin regains his limbs and so does the Feudal Japan illusion. Virgo tells Casey that the ronin is manipulating her mind to see these things, but Casey dismisses her, because she has fallen in love. Casey snaps back into reality after hearing helicopter wings, and tries to escape to the subway, but Virgo blows it up with Casey inside. The ronin telepathically reaches Casey and wakes her from her unconscious state, before Virgo has the chance to kill her. Casey makes her way inside of Aquarius, which has now engulfed much of the city. Virgo taunts Casey as she makes her way to the ronin, but Casey is unaffected. The ronin causes a blackout and Casey finds out from two people in the complex that Peter tried to blow up Virgo, but failed and now is in pretty bad shape.
Casey finds peter, and he tells her that Virgo must be stopped, and the only way is to “make fantasy fail”. After that Peter is killed by Virgo. Virgo sends more robots to get Casey but before they can hurt her, the ronin blows them up telepathically. Casey continues to the Ronin, when she comes across Peter again, except this time Peter has been deformed by cybernetics. He explains how Virgo wants biocircuitry to be the new dominant life form on earth, and one way she is experimenting is by using Billy. Casey is then forced to kill Peter before he could strangle her.
Casey finally reaches the ronin, and is transported back into feudal Japan. Agat appears behind her, but there is no time to free the ronin and Casey had to handle the situation. Remembering Peters words of “breaking down fantasy; making fantasy fail” she shoots Agat in the head instead of using her sword. Casey then frees the ronin, but then ridicules him that a she, a woman had to kill Agat and avenge his master. She then gives him a sword in order to commit seppuku- Japanese ritual suicide. Acting as his second Casey then decapitates him, releasing a telekinetic blast that destroys the entire city, and leaving only Casey and the ronin.