Sarah is a shy, introverted young woman who lives a quiet life and works at a crafts store. In her spare time she visits the grave of her mother, who died by suicide the year before. She also frequents the horse stable where her former horse – Willow – is boarded, and where she rode in her childhood; Sarah’s recurrent visits visibly annoy the owners. On her birthday, she makes a feeble attempt to ask her Zumba class instructor to go out with her but fails to make her point. When her roommate, Nikki, finds Sarah home alone on her birthday, she invites Darren – her boyfriend Brian’s roommate – over for a double date. The four smoke marijuana and have drinks, and Sarah listens eagerly as Darren reveals details about himself and his past relationship. After he leaves, Sarah has a bizarre dream in which she is lying in a white room with a man and woman.
The following morning, Nikki awakens to find Sarah sleeping on the living room floor, and large scratch marks running across the wall. Darren returns to the apartment to retrieve his car, and asks Sarah on a date. At work, Sarah suffers a bloody nose and recognizes a man walking outside who resembles the one from her dream. Later, Sarah spends an afternoon with her childhood friend Heather, who suffered a traumatic brain injury in a riding accident that results in her having recurrent seizures and short term memory loss.
A series of bizarre incidents soon befall Sarah: She hears people talking in her apartment when Nikki is not home, and later one morning finds her car has been stolen from her apartment’s garage. Gary – Sarah’s wealthy stepfather – notifies her the car has appeared at a tow yard, as the registration is still in his name. He brings Sarah to retrieve it, and the tow driver informs them the car was abandoned near a water facility in the middle of the road. Later on, Sarah apparently sleepwalks out of her apartment and awakens standing on a sidewalk, and has unexplained time loss. Her boss, Joan, suggests that Sarah visit a doctor given Sarah’s familial history of mental health problems.
Sarah becomes convinced she is experiencing alien abductions and might be a clone, the latter triggered by a subplot in Purgatory, a fantasy television series Sarah watches regularly. Due to her striking resemblance to her deceased grandmother, Sarah worries she may be a clone of her. Meanwhile, she tracks the man from her dream, Ron, to a plumbing store that he owns. While on a date with Darren, Sarah manically confides her belief that she is a clone, and has him drive her to her mother’s grave to dig her up and retrieve her DNA. When Darren becomes disturbed, Sarah accuses him of plotting against her, and threatens him with scissors, forcing him to leave her there.
After Sarah strips nude at work with no memory of doing so, she is admitted to a psychiatric hospital. There, she recognizes another patient as the woman from her dream; when Sarah describes it, the woman reveals that she has had the same dream. Sarah takes this as confirmation of her belief that they are both alien abductees, and soon joyfully tells her social worker that she is not delusional. Despite his reservations, Sarah is discharged after 72 hours in the hospital and dresses in her grandmother’s dress, covertly stealing Willow from the stable and walks with her into the woods. Sarah stops in a clearing and lies on the ground. Moments later, a spaceship appears; she levitates toward the sky and disappears.