Sarah is a shy and introverted young woman whose life is marked by a profound sense of solitude. She leads a quiet existence, earning a living at a local crafts store while spending her free time visiting her mother's grave—a poignant reminder of her mother's tragic suicide just a year prior. In addition to her somber visits, she finds solace at the horse stable, where her beloved childhood horse, Willow, is boarded. However, her frequent visits become a source of annoyance for the stable owners, who struggle to understand her deep attachment.
On the day of her birthday, Sarah's roommate Nikki discovers her alone and decides to inject some life into the occasion by inviting Darren, the roommate of her boyfriend Brian, over for what was intended to be a double date. The evening takes an unexpected turn as the four indulge in marijuana and drinks. As they converse, Sarah becomes increasingly fascinated by Darren's revelations about his life and past relationship. Unfortunately, the gathering is abruptly disrupted when Sarah suffers from a nosebleed. After the date, she experiences a peculiar dream where she finds herself lying on a stark white canvas, surrounded by a man and woman, both oblivious to the unsettling environment.
The next morning, Nikki awakens to find Sarah curled up on the living room floor, and eerie scratch marks mar the wall nearby. When Darren returns to collect his car, he musters the courage to ask Sarah out on a date—a moment that sends her heart racing. However, while at work, Sarah suffers another nosebleed, and as she recovers, she spots a man outside who bears an uncanny resemblance to the figure from her haunting dream. Adding to her rollercoaster of emotions, Sarah spends time with her childhood friend Heather, who has been grappling with the aftereffects of a traumatic brain injury sustained in a riding accident, leading to her persistent seizures and memory lapses.
As Sarah's life unfolds, she is soon beset by a series of bizarre occurrences that blur the lines between reality and something far more sinister. While driving home one evening, she finds herself inexplicably transported from a red light near a water facility to her kitchen, the tap running as if time itself had slipped away. Alone in her apartment, she begins to hear indistinct voices echoing through empty rooms, and in a shocking turn, her car mysteriously vanishes from the garage.
In a surprising twist, her wealthy stepfather Gary informs Sarah that her car has turned up at a tow yard due to the registration still being under his name. They visit the yard together, and the tow driver reveals that the car was found abandoned near the very water facility where Sarah experienced her disorientation. Later that night, Sarah sleepwalks outside, waking up by a telephone booth, seemingly lost yet again. After her return, she notes that only minutes have elapsed, raising her suspicions further.
At work, her boss, Joan, concerned about Sarah's family history of mental health issues, suggests she seek professional help. This fuels Sarah's paranoia, leading her to believe that she is caught in a cycle of alien abductions. The resemblance she bears to her deceased grandmother terrifies her, as she begins to suspect she could be a clone. As days pass, she starts tracking down the man from her dream, Ron, discovering he runs a plumbing store. In a fit of desperation during a date with Darren, she confesses her fears about being a clone and demands he drive her to her mother's grave to dig up DNA. Disturbed by her erratic behavior, Darren leaves, fearing for his safety.
After a surreal shower experience that sees her transported back to work, Joan grows increasingly worried and contacts the police. Subsequently, Sarah is committed to a psychiatric hospital, where she awakens to find her room's door left ajar. She seizes the opportunity to escape, venturing out to various locations, including the crafts store—where she steals fabric to create protective suits for herself and Willow. However, her confrontation with the stable owner sends her fleeing once more. Seeking solace, she visits Darren, and in a moment of intimacy, they share a passionate encounter, only for him to mysteriously vanish afterwards.
In a deep dive into her subconscious, Sarah constructs a fabric doorway and steps into a white room reminiscent of her previously unsettling dreams. Within this eerie environment, she witnesses shadowy figures tending to unconscious individuals, including herself and the other figures she had seen in her dreams. A sudden leap through a window transports her into Heather's bedroom, reuniting them in slumber. Yet, upon waking, Sarah discovers herself back in the hospital, leading to the grim realization that her recent experiences were merely figments of her imagination. Recognizing another patient as the woman from her dream, Sarah engages her in conversation, learning that they share dream elements that hint at their potential alien encounters. This revelation exhilarates Sarah and convinces her that she is not mentally ill, prompting an approving discharge after 72 hours.
Upon returning home, Sarah chooses to wear her grandmother's dress, then cunningly abducts Willow from the stable. Together, they journey into the woods where, standing in a serene clearing, Sarah lies on the ground and awaits the inevitable moment. Moments later, a spaceship appears before her; she is levitated into the sky, marking her ultimate disappearance into the unknown.
