A woman named Diane is seated with some other parents, at a home school association meeting. After one of the parents talks about how challenging it will be to let her sick child go to college alone, the meeting leader consoles her and asks Diane how she feels about letting her daughter, Chloe, leave for college.
Diane answers positively, saying she feels great. However, all the other parents are shocked by this answer, and the meeting leader tells her to be honest.
Diane goes further to say even though they’ve not gotten any response from the colleges Chloe applied to, she feels happy that Chloe will finally be able to leave the house, and socialize in college.
She also says that even though Chloe is very sick, she’s confident she’ll survive because that’s what she has been doing all her life.
The next day, Chloe wakes up from bed and gets in her wheelchair, to begin her usual morning routine of throwing up in the toilet, taking care of her rash, and also taking her meds. Just after having breakfast, Diane instructs Chloe on what to study for the day.
While at it, Chloe hears the mail truck arrive, and she immediately wheels herself to the door. However, Diane is there, and she tells Chloe that none of the letters delivered are from the colleges she applied to.
She also says if any letter from a college arrives, Chloe will be the first to open it. Chloe looks disappointed as she has still not gotten an update on any of her college applications, but she gets back to work.
Later that day, while Chloe is working on a science project, she complains to Diane about not having a phone to check what’s wrong with her work. Diane plays down the importance of having a phone, and tells her she’ll figure out what’s wrong. After leaving Chloe to do her work, Diane gently goes to the basement with a glass of wine, and there, she starts watching a video of when Chloe was a kid.
Even though she looks happy at the start of the video, Diane’s mood suddenly changes, and she looks disturbed.
The next day, Diane arrives from a shopping trip and drops all the grocery bags in the kitchen. Suddenly, she receives a phone call and goes outside to take it. Meanwhile, Chloe quickly goes to the kitchen to take some chocolate from one of the bags Diane brought in.
After taking all the chocolate she wants, Chloe notices a box of green pills in the bag. As she reads the label, she sees Diane’s name, and starts to wonder if anything is wrong with her mother.
Before she can do anything, Diane comes back in, and Chloe immediately has to drop the grocery bag and return to her work. That night, when Diane gives her some pills to take, Chloe sees that the green pill is also in the cup.
She hesitates to take the pills, and when Diane asks what’s wrong, Chloe says she thought the green pill was for her mom. Diane is shocked to hear this, but Chloe says she saw it while trying to take some chocolate.
Diane immediately changes the topic to something about work, but as she’s about to leave the room, Chloe says she saw Diane’s name on the label. Diane says it’s nothing serious, and it’s because her name was on the receipt. With this, Chloe takes the pills and goes to bed.
The next day, just as Chloe is about to take her morning pills, she decides to go and check the name of the pill. Just as she successfully uses one of her tools to pick up the box of pills, she hears the mail truck and immediately runs to check.
Before she opens the door again, Diane is right there with the letters in her hand. She looks shocked to see Chloe at the door, and reassures her that if any letter comes from a college, she’ll open it first. As Chloe looks around, she catches a glimpse of Diane’s car door still open, leaving her wondering if Diane had run to get the letters, before Chloe did.
Shortly after, Chloe returns to her room, to check the pill she picked from the shelf. To her surprise, her name is now on the label, and she can’t seem to understand it.
As it looks suspicious, Chloe tries to remove the label and sees that Diane actually placed the one with Chloe’s name over the old one, which she even tried to scratch off the container. Chloe is shocked and starts suspecting that something might be wrong with the medication she has been using.
That night, Diane asks Chloe to take her pills, and then leaves her room, but Chloe spits out the green pill and keeps it. She then sneakily goes down to the living room to use Diane’s computer to search for the name she saw on the box of pills.
Unfortunately, there is no internet connection, and she’s unable to find anything. However, she’s unaware that Diane is watching her from the kitchen.
The next morning, Diane complains to a customer care representative about the internet. After the call, Chloe asks when the internet will come back, and Diane responds by asking how she knew the internet was down.
Chloe confesses that she used the computer last night, though she lies that she wanted to look for a solution to the problem with her science project. Diane seems to believe this, and they continue having their breakfast.
Later that day, while Diane is in the garden, Chloe uses the landline phone in Diane’s room, to call the pharmacy where Diane gets all her prescriptions. Unfortunately, Chloe’s voice is recognized by the pharmacist, so she hangs up immediately. She also tries to contact another pharmacy, but when she sees that it will come with a charge that Diane will be aware of, she hangs up again.
Chloe then dials a random number to ask for their help, to check the use of the green pill Diane has been giving her.
The person who answers the phone doesn’t understand why Chloe can’t do it herself, but she explains that she doesn’t have a phone or internet service. Even though the person takes a while to respond, Chloe is told that the pill is a drug for the heart, but it’s a red pill.
She goes into shock and cannot believe her ears, as she realizes that Diane put on a fake label to convince her that it was for her. She pulls herself together and ends the call, after which she looks at the pill and wonders what it’s used for.
That night, Chloe barely touches her dinner, and as Diane looks confused, Chloe mentions that she feels like going to see a movie. Diane is happy with this, and she agrees to take Chloe.
The next morning, Chloe packs all the green pills she has been storing and takes them with her, as she joins Diane on the drive to the cinema.
As they’re at the parking lot, Chloe starts thinking of a plan to distract Diane, so she can go to the nearby pharmacy to ask what the green pill is used for. While the movie is showing, Chloe tells Diane she wants to use the restroom, but as she wheels herself out, she heads straight for the pharmacy.
Many people are on the line waiting to see the pharmacist, but Chloe begs them to let her through, because she needs to make an important inquiry.
Because she’s in a wheelchair, they all let her go to the front, and there, she drops the pills at the front desk and asks the pharmacist, Mrs. Bates, what it’s used for.
Mrs. Bates says it will be easy to find out what it is, as long as it’s part of Chloe’s medication. However, Chloe says it’s for her mom. Because of this, Mrs. Bates says she can’t tell Chloe anything about it, because it’s against the pharmacy’s policy to share other people’s prescriptions.
Chloe looks disappointed and lies that it’s part of a game with her mom, and she needs the answer to win. Mrs. Bates doesn’t seem to believe this, but Chloe continues to beg and convince her to reveal the use of the drug.
Just as Mrs. Bates checks, she says she doesn’t think the pill is anything to worry about, because Diane bought it for their dog. Chloe is shocked and she struggles to breathe after hearing this. She then asks Mrs. Bates what would happen if a human took the pill instead.
Just as Mrs. Bates tries to understand why Chloe asked the question, Diane barges into the pharmacy, shouting Chloe’s name. Chloe immediately asks Mrs. Bates for a response, and she says if a human took the pill, it would make their legs numb.
Chloe suddenly realizes that the pill is the reason why she can’t walk, and as she tries to catch her breath, Diane appears in front of her and tells her everything will be okay. She asks Mrs. Bates to get her an ice bucket, while the customers also move away from them. As she’s alone with Chloe, Diane injects her with a sedative, and she passes out.
After Diane takes Chloe home, she starts thinking of what to tell her when she wakes. She also thinks about sending an email to Mrs. Bates, so that she doesn’t have any suspicions that she’s harming Chloe.
However, she decides against it and searches for household neurotoxins, which can affect Chloe’s brain and possibly make her forget all that happened.
The next day, Chloe wakes up and decides to escape from the house. Unfortunately, she sees that the door has been locked, and Diane doesn’t seem to be around as well.
She picks the lock and tries to open the door, but it doesn’t still work, and she realizes that Diane must’ve put something in front of the door, to make sure she doesn’t leave the room.
At this point, Chloe is left with one option, and she takes a look at the window. After thinking about it, she climbs out the window and lands on the roof. She’s then able to make her way into the house through Diane’s room window. As she crawls in, she starts struggling for breath, and realizes she doesn’t have her inhaler with her.
She quickly crawls to her room, removes the stick in front of the door, and proceeds to get the inhaler. After she uses it, she feels well again and gets in her wheelchair.
As she gets to the stairs and tries to use the wheelchair lift, she discovers that Diane has shut it down, and it’s no longer working. Chloe remains desperate to leave the house, so she throws her wheelchair down the stairs, after which she also throws herself down.
She lands badly and hurts herself in the process. As she tries to get up, Chloe feels her leg move for the first time, and this further shows her that the dog medication was the reason for her paralysis, and it’s now slowly wearing off after she stopped taking the pills. She immediately gets up and wheels herself out of the house.
As she’s moving on the road, she sees a car coming and immediately hides, thinking it’s Diane. However, it turns out to be the mailman. Even though her wheelchair gets stuck in the sand, Chloe uses all her strength to force it out, so that she blocks the road, and the mailman can see her.
The mailman comes out of the truck and recognizes Chloe as Diane’s daughter. He asks what’s wrong with her, and she tells him that Diane has been hurting her, and she needs to run away before she gets back. The mailman decides to help, but as he’s about to take her into the truck, Diane is on her way back from a shopping trip, and she sees them.
Chloe looks scared, but the mailman tells her not to worry, as he hides her in front of the truck. Diane comes down, running towards the truck, but the mailman stops her, saying he can’t let her go close to Chloe.
Diane insists that she needs to see her daughter, but the mailman says Chloe has told him scary things about how she treats her. Diane tells him that Chloe is lying, and she’s under a lot of stress that has started to affect her brain.
This is not enough to convince the mailman, who says he’s taking Chloe to the hospital. Diane finally agrees, but asks if she can follow them.
The mailman says it’s not a problem, and as she returns to her car, he goes to meet Chloe to ask if she wants to go to the hospital or a police station. Chloe chooses to report to the police, and the mailman agrees to take her there.
Meanwhile, Diane goes to her car trunk to open her first aid box, to find something to use to attack the mailman. Just as he tells Chloe that he’ll drive safely and take her where she wants, Diane shows up and stabs him from behind. Chloe is shocked to see this, and as she breathes faster, Diane also knocks her out.
When Chloe wakes up, she sees herself in the basement. She looks around and sees some letters in the trash. As she checks them, she sees that one of them is a letter from her most preferred college.
Chloe opens the letter and breaks down in tears, when she sees that she got in. Out of anger, Chloe scatters the table and can’t seem to understand why Diane doesn’t want her to go to college.
As she tries to move around, she also notices that her wheelchair has been chained. This doesn’t stop Chloe as she gets out of her wheelchair, and crawls to pick a box in front of her. Chloe opens the box and is shocked to see a picture of herself, standing upright when she was younger. She also sees the death certificate of a baby named Chloe.
As she checks further, Chloe also finds a page from a newspaper about a newborn baby that was snatched from a hospital.
With this, Chloe realizes that Diane might not be her mother. It turns out that after Diane gave birth many years ago, she lost the baby on the same day. After crying for a few days, she still couldn’t get over the loss of her baby, so she snatched one from the hospital, which happens to be Chloe.
After Diane carries the mailman’s dead body into the house, she goes to the basement and sees Chloe checking through the box with all her secrets. Chloe immediately says she knows Diane is not her mother, but Diane says she is.
She then starts talking about how she saved Chloe from her real parents, because she’s the best person to care for her. Chloe suddenly realizes that Diane poisoned her, and she was never really sick. Diane says she did it to protect Chloe, but Chloe says everything Diane did was for herself.
Seeing as Chloe is not ready to accept her apology, Diane goes into a room in the basement and drags out a machine, after which she starts mixing the neurotoxin. Chloe gets scared and starts begging Diane not to kill her.
Diane doesn’t listen and just keeps saying Chloe will forget everything that happened, after using what she’s mixing. Chloe quickly crawls into a room and locks it, before Diane can reach her.
As Diane tries to break in, Chloe sees a bottle of a toxic chemical and picks it up. Immediately Diane enters the room, Chloe drinks it up, saying she knows Diane needs her, so she’ll take her to the hospital.
Diane takes Chloe to the hospital, and there, the doctor tells her Chloe needs further mental evaluation, because trying to kill herself at a young age is a cause for concern. Diane is unhappy with this, because she doesn’t want Chloe to wake up and tell the doctors anything.
Meanwhile, Chloe wakes up and sees a nurse in her room. She immediately tries to get the nurse’s attention, and after a while, the nurse sees that she needs something. Chloe points to the nurse’s pen, but the nurse says she can’t give it to her, because she could use it to harm herself.
When she sees that Chloe looks disappointed, the nurse eventually gets her a coloring pen and a piece of paper. As Chloe writes on the paper, the hospital’s alarm goes off, indicating an emergency.
The nurse leaves the room, and a while later, Diane comes in and says she’s taking Chloe away. When they enter the elevator, Diane tells Chloe that they both need each other, and Chloe has to cooperate with her.
However, the nurse returns to the room and sees that Chloe is no longer there. She also sees that Chloe wrote the word mom on the paper she was given. The nurse immediately alerts the security officials to stop Diane from leaving the premises.
To avoid getting caught, Diane takes a different route but realizes that she can’t go any further, because she won’t be able to take Chloe through the escalator. As she’s about to wheel Chloe back, she notices that the wheelchair is not moving.
When she looks closer to see what happened, she is surprised to see that Chloe has put her leg on the floor to stop the wheelchair from moving.
Chloe says she doesn’t need her, and as the security officials arrive at the scene and tell Diane not to move, she takes out her gun and points it at them.
Diane gets shot, and as she struggles to believe what’s happening to her, she falls down the escalator, with Chloe looking relieved as the nurse attends to her.
Years later, Chloe becomes a medical doctor, and she goes to see Diane at a psychiatric hospital.
When she gets in, she starts talking about how her husband and child are doing fine. She also talks about work, and how her favorite thing to do is giving prosthetic legs to people.
Just as Chloe says she’s about to leave, she spits out the dog medication Diane used to give her, and asks Diane to open her mouth, as she plans to give her a taste of her own medicine.