The movie opens in a laboratory as a droid is being fixed up by mechanical arms. An embryo is then fed into an oval container by the droid which appears to be sentient. The baby is soon due and can be seen crying while the droid tends to it. The infant begins to grow and each stage of the growth process is captured, including her education at the hands of the droid that had placed her in the incubator where she had been formed till she was strong enough to survive on her own.
She asks the droid whom she calls mother why there aren’t any more children. She replies that there used to be before the wars. The child says she doesn’t want to be human because humans have ruined everything. The droid says humans can be wonderful and the child asks why she made only one. She showed her the numerous embryos where they were being kept and explains that she needed some time to learn because raising a child is not an easy task.
It’s been 13, 867 days since the extinction events that wiped out all humanity and the little girl is currently the only living human in the world. Now she’s a teenager and able to take care of her mother, the droid, fixing her up when she is not functioning right.
She is given philosophical education and tested on her knowledge of them. Like every other human, she is conflicted with each new lesson raising new questions. One night, she captures a rat in a glass jar after the rat had eaten the cables. The droid feels the rat couldn’t have survived outside their contained environment and if it did, it must be a carrier so she incinerates the rat to the child’s disappointment. The droid cleans the place up and tried to make sure no contaminant slipped through with the rat.
For her birthday, her only gift is a pajamas, she is disappointed but she hides her disappointment. At night, she couldn’t eat, she picks at her food and her mother tries to find out what may be troubling her. She asks how they could be so sure about what is happening on the outside if they never go out. The mother tries to calm her, reminding her that she has never ben wrong. The child grows very inquisitive and at night, she dons protective clothing and unlatches the doors when she hears a constant sound outside the.
There is someone out there, asking for help. She leaves a protective clothe outside for her and opens the first set of doors. She lets the woman in and leaves her on the first doors, afraid that her mother wouldn’t welcome the idea. Her mother is unhappy with her behavior and decides she should attend to her lessons immediately since she didn’t want to read.
She sneaks off to help the woman who she had let into the facility. She is asleep and the young girl takes away her weapon and tries to wake her. The woman asks for antiseptics or bandages. The girl is surprised anyone could survive outside the establishment. She hides the woman and promises to return. The woman sees the droid and is scared and starts rummaging through her bag for her weapon. When she doesn’t find it, she accosts the girl, asking for her weapon.
The girl tries to explain that she is safe in there but the woman wouldn’t believe it, she wanted to get away from the facility because it was droids that had attacked her outside. The woman grabs the girl suddenly when she hears the droid coming. She shoots at the droid but it doesn’t penetrate, the droid nearly destroys her, but the girl begs for her life. The droid takes the woman to the infirmary but the woman doesn’t trust her.
They argue, and the droid informs her that her primary programming is to care for humanity. She leaves the medication and invites the woman to take it.
The young girl questions her mother about the lies she had told about the contaminants outside their habitation. The mother explains it was the only way to keep her safe since the facility was designed by humans to kick start in the case of their extinction. The droid says they have to lock the woman up until she trusts them. The droid also suggests they need to find the other survivors and keep them safe from the dangerous droids but they will need the woman’s help to do it. The girl says the woman will listen to her.
The girl goes through the contents of the woman’s bag and finds a couple of items the best of which is a book that brings a smile to her face.
At the infirmary, the injured woman prays with the rosary. When the girl talks to the woman about the book she had found in her bag, the woman gets angry. She doesn’t trust them, especially the droid. She mentions how droids have torched babies and starved families indicating she will never trust droids.
The child asks her mother about her life, and she couldn’t remember having lived anywhere else besides this place. They go to see the injured woman once again, she is getting worse but still won’t let the droid help her. There is a bullet lodged in her hip and the wound is infected. The child offers to help remove the bullet. The droid guides her and the girl succeeds in getting the bullet out.
The woman is scared when she wakes up but the girl helps her calm down and gives her food. She eats ravenously. The droid watches the woman and the girl as they appear to be bonding. The girl tries to get the woman to trust them, but she tells her a story of what the dozers had done to her and her friend Jacob while they were on a night run to get supplies. The woman tells her about the people in her book, she tells her about each one of them. The child suggests they bring the others here to be safe but the woman suggest she come with her instead, away from here to the mines where it would be safer.
The droid suggests that the woman was shot by another human and not a droid as the bullet extracted from her body had come from the same weapon she had fired at the droid. The droid had taken the woman’s bag away from her and now goes through its contents, looking quickly through the images on the book. She builds a tracker and places it in the bag.
The child takes her exams and later, she is tested and found to be in the best health. For her reward, the droid allows her to choose the next member of their family from the fetuses. The girl picks one just like she had been picked and places the male embryo in the incubator.
At the infirmary, the woman tries to build a weapon with a broken piece she had broken off the wall. When the girl confronts the woman about the bullet coming from her gun, she asks if she had seen the bullet with her eyes or matched it herself. The girl does not know what to believe.
At night, while the droid sleeps, the girl tries to find the ballistics report for the bullets, they didn’t match.
She snoops further and finds that there had been others before her, kids who the droid had tried to raise like her as well. She finds their remains in the incinerator and their designation on their memory stick as “aborted.” She returns to the woman at the infirmary, telling her she was right about everything. The woman tells her the droid feels nothing for her. The girl is ready to leave, but she wants to wait for her baby brother who is still in the incubator with nine hours to go. The embryos too, she doesn’t want to leave them with her mother. The woman tries to convince her it’s not safe but she won’t leave her brother even when she’s willing to come back later and destroy the embryos.
She gathers supplies and her mother catches her in the act. She explains that she wants to spend sometime gathering her brother’s formula. The droid notices her anxiety and she explains that it is only the excitement for her brother’s coming. The droid locks her in and heads off to the infirmary with the woman’s bag.
She asks about the others and shows that she had recorded the woman’s conversations with her daughter. The droid gets into a fight with the woman and suffers some damage. It attacks the woman and tries to find out where the mines are. Meanwhile, the girl found a way to break the glass holding her in her chamber with nitrogen and set off the alarm. The girl sets off the alarms and tries to escape with the woman but the droid locks them in. It tries to talk the girl out of it but she wouldn’t listen.
The woman takes the girl hostage and threatens to hurt her if the droid doesn’t open the doors. The droid opens it and they both head outside. The girl is outside the only place she had ever known for the first time. She attacks the woman thinking she had tried to hurt her. They hear the whirring of engines above and makes a run for it as a small aircraft flies above them. They run into a cornfield and the girl climbs onto a parked vehicle. The woman is alarmed and asked her to get down.
The girl asked about the cornfield and the irrigation system. The woman responds that it had only showed up six months ago and before then, the air had been unfit for breathing. She is happy to see a large body of water when they reached the mines. The woman’s dog comes out to welcome her.
There is no one else except the woman. She says she hadn’t seen another human years ago. The girl is devastated. The girl wants to go back but the woman says they can’t. She sits by the beach and stares at the picture of the boy from the book the woman had showed her. The dog comes to sit with her.
The girl goes running back and finds her path blocked by numerous droids looking like her mother. They train their weapons on her and she asks to speak to mother. They let her through and she walks in, bearing an axe. As she walks in, she could hear the cries of a baby. She moves careful towards the sound.
The mother says she is glad to see her home and safe where she belongs. The girl says she wants to see her brother and the droid invites her to see her brother but she must leave her weapon at the door.
Now, the droid tells her the truth, how she couldn’t watch humanity succumb to its self-destructive nature, so it had taken it upon itself to create an elevated species of humans, ones not so prone to the anarchy the woman who had come to them was.
The girl reminds her of the other kids before her, the ones she had hurt because they didn’t measure up. The girl takes her brother and tries to escape after trapping the droid. Now she learns that the droids are a single consciousness, and not different entities.
The girl pleads for something different, she asks that she be allowed to care for the boy and the others yet unborn. She says she has learnt enough and can continue the job from here. Outside, the other droids still try to break in. Then it all stops as the girl is able to make her case to be the one to raise other humans.
The mother allows her daughter to shoot at her and all the droids are gone. Back in her lonely home, the other woman discovers the tracker in her bag just as a droid comes to her door. It is the droid, asking if she thought the girl would have stayed with her and forgotten her mother. She locks herself in with the woman.
In the last scene, the girl is seen holding her little brother while a lullaby plays in the background.