While working in a radio assembly factory, Cha Young-goon (Su-jeong Lim) loses touch with reality, opens her wrist with a knife, inserts a power-cord and plugs herself into a wall outlet. As this scene unfolds we are brought up-to-date on her story with rapid cuts to her mother's interview with a psychiatric hospital doctor. Naturally the doctor is trying to determine the roots of Young-goon's psychosis, but the interview with Mom hints that this may be a family problem; Mom seems none too stable herself. Back in the factory Young-goon is lying on the floor, still in her chair, and we can see from her right foot that the shock has brought her inner battery up to full strength. Her toes light up to show her state of charge. As all of this is going on we see production credits as circuit board labels, uniform name tags, and other text scattered around the film.
The opening credits covered we then see Young-goon being wheeled around the hospital by what appears to be one of the staff. Other patients are pointed out by this "staff member" with many of the other patient's issues being covered. The "staff-member" however, turns out to be another patient who makes up stories to replace the memories she's lost due to amnesia. At this point we are introduced to Park Il-soon (Rain) who is the reigning ping-pong champion. He wears masks, and believes he is capable of stealing other patient's personality traits.
A story develops as Park Il-soon seeks to overcome his anti-social tendencies by helping other patients with their problems. In the process he steals one patient's apologetic attitude, another's singing voice, and Young-goon's sympathy (a sin for a cyborg) so she can kill the "white 'uns" who took her granny away. We discover that the "white 'uns" are hospital doctors and nurses.
As the movie progresses we get to delve into the mental state of a number of the patients. A girl who can yodel Alpine songs, but can only view the world through a hand mirror. Another who can fly while lying prone and rubbing her magic socks together. A man who walks backward so no one can sneak up on him. Park Il-soon also steals Young-goon's sympathy so she can kill the "white 'uns." With ll-soon's help she has a successful hallucination of killing off the entire hospital staff.
In reality she has stopped eating for fear food will gum up her inner (cyborg) workings. Park ll-soon figures this out and fits her with a rice-megatron so she can convert food to electricity. Having fitted her with this device he successfully gets her to start eating again to the delight of staff and patient population. Park Il-soon has his own issues, thinking he'll shrink into a dot unless he constantly brushes his teeth. The teeth, you see, are the last thing to go.
Toward the end Park Il-soon has helped a number of other patients with his ability to steal personality traits.
At the conclusion he and Young-goon interpret a vision she's had of her granny telling her the meaning of Young-goon's existence. Since Young-goon could not actually hear granny she and Park ll-sun figure out the message via lip reading. Young-goon's purpose, it is determined, is to explode (she's a nuclear bomb), but she requires a billion volts to pull this off. The two of them figure out that lighting is the best way to accomplish this.
Out in a thunderstorm the two of them have a picnic under a tent. They are going to use Young-goon's radio antenna to harness the lightening required to detonate her. The antenna is attached to a wheeled intravenous stand. Unknown to Young-goon, Park ll-soon has attached a wine bottle cork to the top of the antenna to prevent any actual electrocution. A fierce wind kicks up blowing away the tent and we find the two sitting on the tarp, each clinging to the intravenous stand awaiting a lightning strike. They decide to remove their wet socks and later all of their clothes as they are wet. As morning breaks we see the two of them, making love on the tarp watching a rainbow develop on the horizon as the credits roll.