The film begins with a series of images showing all kinds of scientific torture
to children all over the world. One night, a massacre takes place in a children’s ward.
There are search parties deployed in the near forest, looking for a couple of kids on the run.
One of them is a girl, who flees to avoid the same fate as the others in the ward.
The search group manages to catch the other one, a little boy who is brought in front of Dr. Baek.
She complains about the loss of the girl, but concludes that it was no easy task to catch her,
given the kids’ special conditions. She tells the search leader, Mr. Choi that the girl’s
condition is different from his’, so they decide to leave the girl out, believing that she won’t
survive for long anyway. In the wee hours of the morning, a farmer finds the missing girl,
who is dirty and in terrible condition. He and his wife have a doctor see her, and he tells them that
her condition will be stable and she will recover. However, the doctor believes that the girl may
be suffering from amnesia, forgetting both her name and age. The farmer’s wife, upon leaving,
senses how the unconscious girl still has the strength to hold her hand, beginning a bond in
the process. Ten years later, the girl, now named Ja-yoon, grows up with Mr. and Mrs. Koo as if they
were her real parents. Ja-yoon drives and does the family chores due to her parents’ delicate
condition, living a relatively normal life in the countryside. During the family dinner,
news reports of an alleged murder of a geneticist and negative events in the livestock economy cause
Mr. Koo to question whether to sell some of his cattle, much to Ja-yoon’s chagrin.
That same night, Ja-Yoon suffers from a terrible headache after taking a shower,
and then researches Alzheimer online to know more about her mother’s condition.
The next day, Ja-yoon meets her friend Doh Myung-hee at the bus stop. On the road, Myung-hee
tells Ja-yoon about a TV contest called ‘Birth of a star,’ which offers $500,000 as the top prize,
and says that the money could help her support her family’s livestock and improve her mother’s
health. Ja-yoon auditions for the contest, where she’s told that although she may not sing well,
at least she has intelligence and beauty to back her up. To everyone’s surprise, Ja-yoon
gets a perfect score to participate later in the show. The Koo family and Myung-hee watch Ja-yoon’s
audition at night, giving them compliments on her performance. Suddenly the atmosphere gets tense
when on the show, Ja-yoon is asked by the hosts if she has a special talent, and she replies that she
can do some kind of ‘magic,’ something that upsets her parents, reprimanding Ja-yoon. Myung-hee tells
them that they have nothing to worry about, as it will only earn her extra points on social media,
but before she can continue defending her friend, the phone rings, Myung-hee answers,
only for the speaker to go silent. When Myung-hee goes to sleep, Mr. and Mrs. Koo talk to Ja-yoon
about the dangers of exposing herself too much to the public. While her mom is worried, both
her dad and Ja-yoon are reassured that she won’t win and will stay there with them, but with some
extra money. Just before going to sleep, Ja-yoon suffers another headache, detecting that there are
some men in the mountains watching her family. The next day, the girls ride a train to Seoul, sharing
boiled eggs that Ja-yoon promptly devours. They are interrupted by the laughter of a mysterious
boy sitting across, who claims to know Ja-yoon, even calling her by the nickname ‘Ms. Witch.’
He goes so far as to intimidate her, telling Ja-yoon that there’s no need to hide any secrets,
speaking in English, but soon the boy realizes that Ja-yoon doesn’t know anything
about what he’s talking about. To check his suspicions, the boy almost slaps Ja-yoon,
but stops his hand just before impact, detecting something that leaves Ja-yoon crying. After
Myung-hee makes a fuss against him, the boy ends up leaving them, but tells Ja-yoon to meet again.
While switching wagons, the boy effortlessly kills a guy he accidentally bumped into, and
throws the corpse off the train. Even though the girls are late for the live program, Ja-yoon ends
up giving an excellent performance, so much that she manages to advance to the quarterfinals. As
the program airs, Dr. Baek and Mr. Choi recognize Ja-yoon on TV, marveling at how the missing girl
managed to survive in the end. After leaving the competition, Ja-yoon suffers another headache that
forces her to go to the bathroom to calm down. In a flashback during a checkup at the neurologist,
the doctor tells Ja-yoon that she needs an expensive surgery, and that her life is a race
against time. When Ja-yoon asks how long she has left, the doctor tells her one to three months,
and that a marrow transplant from her birth parents is the only way to make it effective.
Back in the present, Myung-hee finds Ja-yoon, and tells her that they must return to the train. They
try to take a cab, but instead, a car parks in front of them, with bad-looking guys surrounding
them. They claim to know Ja-yoon, but thanks to some kids passing by, the girls manage to
distract the men and get into a cab. On their way back home, Myung-hee leaves Ja-yoon alone for a
moment at the bus stop, and in front of her parks the same mysterious boy from the train, who starts
talking in both Korean and English about the men from before to see if Ja-yoon understands him,
but she’s speechless. The boy says goodbye, telling Ja-yoon that she’d better go home.
After the boy leaves, Ja-yoon runs off looking for a cab and tells Myung-hee to ask his dad to come
to his house to make sure his parents are okay, since he’s with the police. Officer Doh does this,
and intercepts the van of the mysterious boy, who is accompanied by some henchmen.
Upon arrival, the girls don’t find officer Doh and Ja-yoon detects danger inside the house, only
to find her parents and the officers playing in the living room, with no sign of the mystery boy.
As they say goodbye, Officer Doh asks Ja-yoon if she knows the guys from before, commenting that
they are actually Americans. Ja-hoon tells him that she doesn’t, and that she might have been
mistaken for someone else. In the next scene, a man goes to a rural resort with his driver.
When he arrives, he finds the dead bodies of his family in the greenhouse, and the mysterious guys
being the killers. Apparently, they were supposed to kill the man, but not happy with that, they
proceeded to kill his entire family. The driver goes to the man’s rescue with a gun, but he’s also
intercepted by the mysterious boy, who injured him off-screen. The helpless driver tries to defend
himself, but the boy uses some sort of telekinesis to trigger the gun in front of him, and causing
the driver to shoot himself against his will. The group set the place on fire and drives off. The
next day, Dr. Beak reads in the news how a gene researcher died with her family in a house fire.
She discusses with Mr. Choi about the girl’s situation and tells him not to worry for her,
even though he wants to do something about it. The woman also asks Mr. Choi about his condition,
and he reveals that under his gloved hand there’s black, lumpy skin. Another of the gene researchers
asks Mr. Choi to kill the girl, but to bring her brain to study her special condition. Meanwhile,
Myung-hee discusses the possibility of a fan club for Ja-yoon and her future stardom over family
dinner, but everything is interrupted when Mrs. Koo wonders why she and her husband are eating
together with a couple of strangers, wanting to know where their daughter had gotten to. Ja-yoon
tries to calm her down, but it is shown how her mother’s condition has worsened to the point of
not recognizing her. Before going to sleep, her mother reveals that she found evidence about
Ja-yoon searching for her biological parents. Already sleeping, Ja-yoon gets a new headache,
not realizing that her house has been broken into. When she realizes this and goes to get
her parents up, a gun is pointed at her head, finding that her house is full of mercenaries
holding Myung-hee hostage. They’re the same guys who had offered them a ride to the train before,
and their leader reveals that this isn’t the first time he and Ja-yoon have met, and how she was
the cause of his multiple scars. Ja-yoon tells him that he’s mistaking her for someone else,
and just as they slightly cut Myung-hee neck, Ja-yoon manages to wriggle free of her shooter,
and uses his gun to kill all the mercenaries there. Now she takes on the leader on her own,
defeating him easily. Ja-yoon kills the man and feels herself awakening from a trance,
only to find a fearful Myung-hee by her side. The mysterious boy appears on the scene,
and reveals that his group is also in the house. He congratulates Ja-yoon,
thinking that her memories finally came back. He then asks to a scared Myung-hee if she thinks her
friend is weird, since she has an above-average level of intelligence despite never studying,
in addition to her innate gifts in singing and dancing, and learning a language just
by hearing it once. Ja-yoon doesn’t really know what the young man is talking about,
so he ends up believing her and asks her to accompany them to recover her memories.
Despite her friend’s advice not to go, Ja-yoon agrees to go, under the threat that if she
doesn’t, they’ll kill everyone she knows. During their car ride, the mysterious boy reveals that
having come to the Koo farm as a child was no coincidence, but that Ja-yoon had selected them
because they were more vulnerable to having a kid after they had lost their son and grandson. They
take Ja-yoon to an abandoned complex, the one that used to house her and the other special children.
Ja-yoon is placed in a glowing experimentation room, where she hears Dr. Beak’s voice.
Dr. Beak believes Ja-yoon’s alibi of amnesia due the brutal damage during the night she escaped,
and that if she still had her memories, she wouldn’t have exposed herself so easily on TV.
Ja-yoon is injected with a substance that triggers her past memories. Now she remembers all the cruel
experiments years ago. Dr. Beak claims to be the best brain specialist in the world,
and to be the one who created Ja-yoon, giving superhuman abilities to the girl. Her plan at
the time was to train a series of gifted children as weapons, but there was a change of plans when
she learned of the side effects the children went through when they were transplanted with
modified physical genes. The children began to become aggressive, and were harder to contain.
Ja-yoon was the closest specimen to perfection, but fearing that she was going
to get out of control, HQ wanted her and other children erased, ending Dr. Beak’s research.
Despite refusing, she ended up accepting it, but she underestimated Ja-yoon’s abilities that night,
so the girl escaped far away. They never believed that a weapon like Ja-yoon could have a normal
life, so they left her for dead, at least until she appeared on the TV show and showed off her
telekinetic ability. Dr. Beak tells Ja-yoon that because of her condition, the migraines
are getting worse, and that she will die of a hemorrhage at any moment. Ja-yoon is in agony, and
they end up injecting her with a second dose that will unlock her 100 percent, though it will only
last for a month. The woman says that from now on, Ja-yoon will need one dose of the substance
per month in order to survive. The situation takes a turn when Ja-yoon reveals that her true plan was
to have that substance in order to be free from her pain, something the mysterious boy notices, so
he and his henchmen decide to go to the scene. Now Ja-yoon remembers everything, managing to outwit
the communication equipment, killing her guard and getting hold of a weapon. Dr. Beak releases some
gas in the room before it’s too late, but Ja-yoon manages to hit an exit in the ceiling vents.
She gets through to the next room, and points toward the doctor. Ja-yoon confesses that this
was her plan all along, to go unnoticed and then find the doctor and her criminal group,
and have them give her the cure for her illness, a plan she has kept secret for years.
Ja-yoon assures that she will kill everyone who hurt her in the past and shoots the doctor in the
knee, asking where the rest of the cure is. Mr. Choi’s group arrives at the building and has a
confrontation with the boy’s henchmen, but loses in the process. The only one left standing is Mr.
Choi himself, revealing that he is the same one who had trapped the kid during the night Ja-yoon
escaped, this kid being the mysterious boy. In the commotion, the boy makes his way to where
Ja-yoon is, attacking upon finding her. They both trash-talk each other about the night they
ran away, and before he can do anything, Ja-yoon charges at the boy, showing her clear superiority.
The two have an intense fight, receiving sharp impacts, but with no significant injuries.
Ja-yoon taunts the boy by subduing him several times, and even though he hurts her,
she doesn’t even flinch. Ja-yoon ends up throwing the boy through the wall into the control room.
She grabs her gun and reshoots the doctor, who was trying to escape across the hall.
The boy takes another gun and shoots at Ja-yoon. They both use their telekinetic abilities,
but Ja-yoon is still in the lead. Even a clear cut through her hand can’t stop Ja-yoon, who
has a super-fast regenerative system. Just before taking out the boy, Ja-yoon is shot in the back.
It was Mr. Choi, who also shoots one of the mysterious young man’s colleagues in the head
just before she kills the doctor. Dr. Beak thanks Mr. Choi for saving her, but before
she can say something else, Mr. Choi kills her. The boy’s colleague manages to get to her feet,
and lunges at Mr. Choi. The two engage in a rather close fight, but Choi manages to win,
only to realize that he has Ja-yoon on his tail. He tries to take her on, but he’s no match for the
perfect specimen, who takes him out completely. Ja-yoon has one last conversation with the boy
before killing him, but he shows her the last dose of the cure. He extorts Ja-yoon by telling
her where the rest of it is, but this is just a distraction for his colleague to attack her
from behind. However, Ja-yoon blocks and blows up her face. Even though the boy is behind her,
pointing a gun at her, Ja-yoon is powerful enough to freeze him. She stabs him several times,
and before she shoots, the boy makes her question whether it’s all worth it, since at the end of the
day, their condition doesn’t allow them to live for long, and Ja-yoon can’t go back to the life
she used to have before. She tells him that she doesn’t care and will continue to live as Ja-yoon.
She asks again where the other cure doses are, but the boy scoffs and refuses to talk. Everything
goes dark and a gunshot rings out. Ja-yoon manages to find the other doses in the building,
abandoning it on her own as she did years before. Watching her flee, the facility is seen to
explode, eliminating all evidence. Ja-yoon returns to the farm, which is surrounded with patrols,
so she just decides to run away. The next scene shows Mr. Koo next to his unconscious wife in the
hospital, sensing the arrival of his daughter. Ja-yoon offers Mr. Koo the case with the cure,
telling him to use it on his wife for eight months so her condition will stop worsening.
When Mr. Koo asks Ja-yoon if she will need the cure, she says a couple of doses will be fine.
Before leaving, Mr. Koo explains to Ja-yoon that some of their livestock died when she appeared in
their lives, so he feared that they were raising a witch. He confesses that he had regretted adopting
her, but the factor that changed that was his wife, convincing him to raise Ja-yoon together,
and make her a lovely child. It all ends with Hyung-mee in the hospital, watching from the
distance as her friend walks away alone. Three months later, at a seaside house, Ja-yoon appears
in front of a woman in a wheelchair, showing her a briefcase full of doses of the cure. However,
Ja-yoon says she needs something more permanent, so she asked for her help.
The woman calls someone else in the room, and Ja-yoon tells this new guest,
a girl with scars on her face, that if she lays a finger on her, she will kill her.