The film starts off with a birthday cake being lit in the dark. An unseen figure humming "happy birthday" carries the cake into a room but then drops it in shock as we see another unknown person commit suicide by hanging herself.

Su-kyoung is lying on an operating table ready to undergo plastic surgery. She is extremely nervous and frightened and is being comforted by her friend Hyeon-su. Hyeon-su's parents are divorced. She leaves and we are introduced to her mother Yoon-hee who is a successful and talented plastic surgeon. The two talk and we are shown that they have a good mother-daughter relationship. Meanwhile, Su-kyoung is alone and panicking in the operating room. She sees a frightening image of a girl wearing a dark blue dress and long dark hair covering her face. The girl crawls underneath the table and disappears from view. Yoon-hee then appears and begins the surgery, telling Su-kyoung that it is time to become pretty. A day later it is Hyeon-su's birthday. She argues with her mom about where to have the party, with her mom finally convincing her to do it in her home (she is very rich).

Hyeon-su is later in her art class, making a sculpture of Su-kyoung's face. Many of the girls in the class comment saying that Su-kyoung looks much more attractive than she did before and wonder whether she dieted or had surgery. Hyeon-su is then spoken to by another or her friends Jae-hui who asks her to comment on the fantastic eye job that her mother performed on her. As the two girls talk and laugh, Hyeon-su accidentally cuts into the face of her sculpture. Su-kyoung notices and a large cut appears on her cheek. She screams and flees in terror. She descends into the building holding her bleeding face. A mysterious voice shrieks at her saying she wants her face back. Hyeon-su appears and asks her if she's okay, Su-kyoung's cut and blood vanishing. Hye-won, another girl who is friends with Hyeon-su is deciding whether to get an eye job or nose job from Yoon-hee. She decides on an eye job.

Meanwhile Hyeon-su, Jae-hui and Su-kyoung wait at a bus stop while an old woman gives out fliers for her missing granddaughter. Su-kyoung is distant, troubled by earlier events. The bus arrives but Hyeon-su waits for her friend Sung-eon to come. Jae-hui shows instant disgust at the news but is not given time to argue as the bus drives away. Sung-eon is a tomboyish type and is closer to Hyeon-su than her other friends who she doesn't get along with well, she also hasn't undergone any plastic surgery. Sung-eon appears on a motorbike and the two drive towards Hyeon-su's house.

Jae-hui and Su-kyoung wait outside Hyeon-su's house. Jae-hui complains for a while, but when Hyeon-su and Sung-eon arrives she again shows her dislike of the tomboy girl. The girls then celebrate Hyeon-su's party and Su-kyoung gives her an expensive doll for a present. When lighting the cake, the same girl that Su-kyoung saw when she went under the knife appears next to Hyeon-su, but no one else can see her except Su-kyoung. The candles go out. In a hasty panic, Su-kyoung gets in the way of the cake (which was to be thrown at Hyeon-su) and then goes to the bathroom to wash her face. Su-kyoung admires her face for a second before she sees her face shredded in the reflection. She screams and runs from Hyeon-su's house with Jae-hui blaming Sung-eon and giving her a nasty look before leaving. Yoon-hee asks what the problem was but Sung-eon reassures her that everything is fine. Later the two girls look through a photo album and laugh about what they used to look like. Hyeon-su then tells Sung-eon that she has no childhood pictures. Yoon-hee listens through the door and then walks away.

Su-kyoung meanwhile has locked herself inside her room for days and refuses to see anyone. Her mother calls Yoon-hee and Hyeon-su to come and help. Su-kyoung lets Hyeon-su in and she tells her that there is something wrong with her face and that she can't help wanting to mess it up. Hyeon-su hugs her but Su-kyoung hears another voice say "pretty" and fearfully forces Hyeon-su out. Hyeon-su bangs on the door and Su-kyoung looks into a broken shard of mirror, suddenly the ghost girl reappears and we see a closeup of her blue eye. She then says "I'll make you pretty" before laughing evilly. Su-kyoung's face begins to violently cut open and she screams, squeezing the shard of mirror until her hand bleeds. Hyeon-su and the other women manage to enter the room after Su-kyoung's screaming stops. Hyeon-su finds the dead Su-kyoung face down and flips her onto her back, revealing her face, now cut off on one side. Her mother screams.

During art class the next day, Hye-won talks dirty of Hyeon-su and blames Su-kyoung's death on her. Hye-won has had surgery from Yoon-hee. Jae-hui confronts her and threatens her and calls her a "Fucking tramp!" leading to an argument that Hyeon-su angrily interrupts. At their home Yoon-hee discovers that Hyeon-su is into Vivaldi and has been calling her father (who doesn't live with them after the divorce). Later Yoon-hee gives Hyeon-su a facial, covering her entire face. While Hyeon-su sleeps a pair of mysterious hands begin to caress her face before trying to gouge out her eyes with their thumbs. Hyeon-su panics and tears off the face mask, sees no one with her and her mother then comes to comfort her. The two share a loving moment before her mother places her face mask into a box in the other room.

Hyeon-su then goes into the basement where she was told never to go there as a child. She explores the creepy place and finds a picture of a child with a severely burnt face and the words, Hyeon-su before surgery. The girl with long hair has been watching Hyeon-su but suddenly vanishes when her mother comes down and scolds her. Hyeon-su then becomes distant and refuses to speak to her mother properly.

At a pool party Hye-won goes and sits next to Jae-hui and the two apologize for their behavior. Jae-hui then asks her if she saw anything strange when she went under the knife, which Hye-won silently confirms. The two girls get scared and go to ask Yoon-hee what's going on. Yoon-hee simply tells them that they are just edgy because of Su-kyoung's death, much to the relief of the two girls.

Hyeon-su then leaves the house to see her father. She and Sung-eun take the motor bike and head towards their destination, with Yoon-hee carefully following them.

As Hyeon-su talks to her father, Yoon-hee has a flashback. Many years before, she tells Hyeon-su to wait in the car while she delivers a file to her husband. She promises a trip to the park for Hyeon-su, who says no in a bratty way. As Yoon-hee enters the building, the car's engine begins to smoke. Yoon-hee finds her husband and a woman engaging in oral sex, hits him on the head with the folder and leaves. He runs after Yoon-hee and as she and him argue, the car's engine explodes, horribly burning Hyeon-su, leaving her comatose and close to dying. Yoon-hee weeps at the hospital over her disfigured sleeping daughter. She then later visits a church and a little orphaned girl grows attached to her wishing to go home with her, addressing her as mommy. The Orphaned Girl loves Yoon-hee very much and the two are shown to have a loving mother-daughter relationship. Yoon-hee's husband then goes to the hospital to find Hyeon-su missing. The Orphaned Girl soon ventures into the forbidden room and sees the bedridden disfigured Hyeon-su through the door. She asks Yoon-hee if the girl is sick and Yoon-hee says yes before telling her that she can never see her. The Orphaned Girl accepts this before running off into the basement happily.

Back in present day, Hyeon-su and her father discuss the photograph and Hyeon-su leaves. Yoon-hee confronts her ex-husband and tells him that he has no right to see Hyeon-su. Her ex-husband then argues saying that she isn't Hyeon-su and that she is the Orphaned Girl. Yoon-hee responds by saying "She's MY daughter". As Yoon-hee leaves and stands in the rain with an umbrella she sees a dripping wet Hyeon-su, who tearfully says "mom" and hugs her.

Yoon-hee takes her home and tells her to have a bath. The doorbell rings and Yoon-hee goes to see who it is, horrified to find out it is Hyeon-su ringing the doorbell. As she lets Hyeon-su in, the two get into an argument in which Hyeon-su tells her that she isn't her real mother which causes Yoon-hee to slap her. As Hyeon-su locks herself in her room, Yoon-hee notices the floor is soaking wet and then hears the tap in the bathroom running. The bath is overflowing and filled with bubbles. a pale hand grips the side of the bathtub but then slides back into the water as Yoon-hee enters. As Yoon-hee turns the tap off and unplugs the bath, footsteps leave the bathroom and head towards Hyeon-su's room. Hyeon-su's door opens on its own and as Hyeon-su checks it out and sees her mother walk down the far end of the corridor, her bed suddenly becomes wet. Hyeon-su sits on it, notices the wetness and finds a tangled bunch of wet long hairs on her back and screams. She pulls back the covers to reveal the girl in the blue dress lying soaking wet under the sheets. She screams again and the girl disappears.

The next day Hyeon-su shows the picture of the missing girl from the old woman to Sung-eon and then shows her a photo given to her by her father. Sung-eon notices that they look very similar but have different eye colors. Meanwhile Jae-hui and Hye-won are painting self-portraits. Hye-won goes to the toilet while Jae-hui washes her paint brush. She notices it gets stuck in the middle of the bucket of paint-water. As she inspects it a hand shoots out of the bucket and forcefully pulls her head into the bucket by grabbing her face. Jae-hui accidentally tears her picture. Sung-eon gets a call from Hyeon-su's mom. Hye-won returns and is shocked to see the painting ripped and scratches on Jae-hui's face, who now seems to be almost catatonic and in a trance-like state. Next we see the two girls sitting face to face and smiling in a possessed way as they draw lines on their faces, telling each other which parts of their faces need improving. They then lift up two scalpels and begin to slowly cut each other's faces up, both uttering "I'll make you pretty" at the same time, with their feet in the bucket. Hyeon-su and Sung-eon both enter the room to find both of the girls soaked in blood with shredded faces, smiling at the two of them. The ambulances come and the paramedics carry Jae-hui's and Hye-won's bodies away on stretchers (they presumably died of blood loss). Sung-eon is taken downtown to answer questions about the two girls.

Yoon-hee comes to the scene of the crime and leaves with "Hyeon-su". The real Hyeon-su returns home and her mother locks her in the basement. Yoon-hee puts what she believes to be Hyeon-su to bed and leaves her room before she has another flashback. Hyeon-su, still with her face burned off begins to show signs of improvement and Yoon-hee then performs an operation. Yoon-hee then removes the girl's oxygen mask but cannot bring herself to kill her and then quickly gives it back as she sobs with guilt-ridden sadness for her "daughter"; the faceless girl lovingly strokes her mom's hand. Later, the little faceless girl (head wrapped in bandages) watches the other girl play with a friend (Sung-eon?) outside and she comments on how pretty she is. Yoon-hee tells her that she is "way prettier" but the little Faceless Girl accuses her mother of liking the other girl better. Yoon-hee then lovingly tells the Faceless Girl that she will make her a new face. Unfortunately Yoon-hee didn't fully keep her promise, and only made the girl very realistic masks of her daughter's face (the face mask seen earlier in the film was used). The Faceless Girl (now in her late teens) sneaks out of the basement and witnesses Hyeon-su's birthday party with all of the friends who would later have surgery. Yoon-hee then hastily leaves the room and locks her back in the basement. The Faceless Girl screams, begging for a birthday party and a pretty face as Yoon-hee breaks into tears on the other side of the door. Later in the day, Yoon-hee prepares a cake (the beginning of the film) and takes it to her, finding out that she has hung herself.

Hyeon-su then discovers the girl's room and explores finding a cupboard filled with the masks she wore over the years and a diary filled with sadness and hate towards Hyeon-su and her friends. Hyeon-su then discovers a fridge-like device which Yoon-hee kept the Faceless Girl's body in after her death. Sung-eon, now free of the police visits Hyeon-su's house and breaks in, unlocking the basement door and the two separate to search for Yoon-hee. Sung-eon then sees what she believes to be Hyeon-su but it is actually the Faceless Girl who shocks Sung-eon to fainting by pulling her own face off like a mask. Hyeon-su finds the unconscious Sung-eon; her mother then appears and drugs her.

Hyeon-su lies on an operating table next to the corpse of the Faceless Girl, who is wearing a mask that resembles Hyeon-su's face. Yoon-hee removes the mask, revealing the faceless girl's gruesome visage properly for the first time. Hyeon-su begins to panic, but she can't move because of the drugs. Yoon-hee tells Hyeon-su it's time to give her face back and begins to operate with a scalpel but stops when she remembers how much she loved her. Yoon-hee collapses to the floor in grief but the corpse of the faceless girl gets up and tries to cut off Hyeon-su's face screaming "I want my face back!". Yoon-hee stops her, telling her that she's her precious daughter and that she's sorry for all she did to her. The ghastly faceless corpse reverts into the child she once was. The Faceless Girl was The Orphaned Girl all along, not the real Hyeon-su and the operation had been a face swap. Yoon-hee had cut off the Orphaned Girl's face and had given it to Hyeon-su. Yoon-hee then repents for her sins and leaves with the Orphaned Girl to go onto the Afterlife. However, the final scene shows the Orphaned Girl, back in her faceless long haired form suddenly appearing by Hyeon-su's bed with her hands reaching out before the credits roll, perhaps meaning that she was not yet satisfied and still wanting her face back.