What Is Sleepwalker About?
The premise of Sleepwalker in 277 words, with nothing given away. The full story follows below.
In the wake of a personal tragedy, Sarah Foster finds herself unable to sleep, the night stretching into a relentless void that blurs the line between wakefulness and dream. Desperate for relief, she turns to a specialized sleep clinic, a sterile sanctuary where science and the subconscious intersect. The clinic’s quiet corridors promise answers, but they also whisper of a deeper unease, hinting that the very act of sleeping might pull her into a world where the familiar becomes unsettlingly foreign.
The clinic’s team—led by the composed Dr. Cooper and supported by the methodical Dr. Koslov and the introspective Dr. White—begins to monitor Sarah’s brainwaves, seeking patterns in her fragmented nights. As she settles into a routine of observation, subtle dissonances emerge: names on paperwork shift, a roommate’s presence feels off, and her sense of self flickers like a candle in a draft. The mundane details of daily life start to feel like clues in a puzzle she never asked to solve, and the gentle hum of laboratory equipment becomes a soundtrack to her growing disorientation.
The film unfolds as a psychological thriller that balances clinical precision with atmospheric dread. Every hallway, every whispered conversation, and every fleeting glimpse of a dreamscape is rendered with a muted palette that amplifies the feeling of being caught between two realities. Dawn, Sarah’s roommate, adds a layer of ordinary intimacy that is constantly threatened by the strange, shifting world around them. As Sarah navigates the thin line between treatment and turmoil, the audience is invited to experience the same fragile tension—questioning what is real, what is imagined, and how fragile the mind can be when the night refuses to end.
What Happens in Sleepwalker?
The complete story of Sleepwalker, from the first scene to the last, in 742 words (about 3 minutes). Spoilers throughout. Names in the text link to 5 cast member pages.
Spoilers ahead
After the suicide of her husband Jonathan Grey, college student Sarah Foster begins to experience dangerous episodes of sleepwalking. Her former professor, Dr. Cooper, suggests a stay at a sleep clinic, where Dr. Koslov and Dr. Scott White monitor her brain activity. Following a night of dreamless sleep, she wakes in a different room, and Koslov informs her that she has been moved for further observation and should stay longer. The unsettling switch between realities becomes the first hint that her perception is not stable.
Soon, she encounters a troubling social mismatch: a professor and her roommate, Dawn, call her “Miss Wells” instead of Foster, and her personal documents identify her as “Sarah Wells.” The mystery deepens as Koslov presents a form about a dream of being chased, though she insists she has not had any dream and that the handwriting on the form resembles hers, even if she cannot accept it as hers. The sense of losing control grows as her nights of dreamless sleep give way to fragments that blur memory and identity.
In spite of her efforts to keep a grip on reality, Sarah learns about selective memory loss and partial retrograde amnesia, a clue that life-altering gaps can exist in the mind. Back at home, her apartment reveals another shock: her roommate has been replaced by a stranger named Nichole, and a phone call from a man who claims to know her adds to the confusion. Dr. Cooper does not recognize her, leaving her more alone in the maze of memory and dream.
That night, she dreams of suffocation, a haunting omen that echoes through the days that follow. The next morning, she wakes up in a strange house, locked out of her own apartment, and finds Nichole and another girl inside. After breaking in through a window, she discovers unfamiliar belongings and a menacing taunt over the phone. She hides in the laundry room as water seeps under the door, a surreal invasion of her private space that mirrors her fractured mind.
When she returns to the clinic routine, everything seems normal again and Dawn is back on the scene. Sarah seeks help from White, who reaches out to Cooper, and Cooper begins to remember her. White explains that the sleep issues can warp perception and that dreams might serve as a bridge to understanding emotions. Outside, a dark-haired man begins to chase her, but White arrives to offer a ride and to illuminate how dreams can reveal buried feelings and motives.
Her dreams intensify: she envisions being trapped in plastic and wakes again in the strange house, this time confronted by a fearful woman who feels all too real. Back in her own apartment, the strange belongings reappear, and in the lab Koslov does not recognize her, while another man named White claims to know her. During a campus lecture, a woman in the audience recognizes Sarah, further destabilizing her sense of self. She evades the police outside her apartment and returns to the laundry room as water again begins to seep in around her.
Eventually, Sarah wakes at the sleep laboratory to hear White confirm that the police found her sleepwalking. Though she cannot recall the events, the data clearly shows she was dreaming. White suggests that the stalker might be the key to linking the two competing realities. Reading through her diary, she discovers a shocking truth: Jonathan was murdered, even though she believed he had killed himself.
Back in her apartment, an assault by a dark-haired man disrupts the fragile sense of normalcy, but White arrives to ensure she remains unharmed. Cooper advises Sarah to seek protection while her condition stabilizes, and the pieces begin to align: the stalker is named Warren Lambert, and memory surfaces in the wake of another attack. The danger becomes personal as the case unfolds, and Sarah finds herself drawn to an intimate moment with White, even as the lines between dream and waking life blur further.
During sleepwalking, Sarah encounters the woman from her dreams, realizing she is part of that other woman’s nightmare rather than a separate foe. The truth comes into sharper focus: she is actually Anna Wells, the obsessive fan who shot Jonathan. The original Sarah—the real woman—was the one Jonathan ended up with. Flashbacks reveal Anna in a coma, gasping for breath while contending with an identity she cannot bear, trapped inside a mind that mistakes her own past for another life altogether.
Sleepwalker Timeline: Every Key Event in Order
12 key events in the order they happen, from “Admission to sleep clinic and initial monitoring” to “Anna Wells and the mind's trap”. 12 events name a place, across 11 locations.
- 1
Admission to sleep clinic and initial monitoring
After her husband's suicide, Sarah Foster begins sleepwalking and is sent to a sleep clinic for evaluation. Dr. Koslov and Dr. White monitor her brain activity as she endures a night of dreamless sleep, waking up in a bizarrely different room. Koslov informs her she has been moved for continued observation and should stay longer.
Where:Sleep clinic
- 2
Identity confusion begins
A professor and her roommate Dawn start calling her 'Miss Wells,' and her documents identify her as Sarah Wells. Koslov shows a form about a dream of being chased, but Sarah insists she never dreamed and questions the handwriting, which she says matches hers. The discrepancy deepens the mystery of who she really is.
Where:Sleep clinic and campus paperwork
- 3
Memory loss research surfaces
She searches for information on selective memory loss and learns about partial retrograde amnesia. The medical explanations hint that memories can be altered or misattributed in sleep disorders, foreshadowing how her experiences may blend with someone else's. The idea plants seeds about a fragile sense of self.
Where:Library / online research
- 4
Nicole replaces the roommate; eerie calls
Back at home, Sarah finds her roommate replaced by a stranger named Nicole and receives a phone call from a man who claims to know her. Dr. Cooper does not recognize Sarah, further eroding her grip on reality. That night, she dreams of being suffocated.
Where:Apartment
- 5
Strange intrusion into reality
The next morning, she wakes to find herself locked out of her apartment and discovers Nicole inside with another girl. After breaking in through a window, she sees unfamiliar belongings in her room and a taunting man on the phone. She hides in the laundry room as water seeps under the door, realizing the events could be intruding on her waking life.
Where:Outside apartment / strange house
- 6
White's guidance and a street chase
Dawn returns to a normal routine, but White explains that sleep issues can warp perception of reality. A dark-haired man begins chasing her on the street, but White intervenes and offers her a ride, framing dreams as a way to understand her emotions. This guidance hints at a deeper connection between dreams and danger.
Where:City street / campus
- 7
Plastic trap dream and the eerie house
She dreams of being trapped in plastic and wakes to find herself back in the strange house, where she is confronted by a fearful woman. The dream imagery begins to bleed into her waking life, blurring the boundary between fantasy and reality.
Where:Strange house
- 8
Lab confusion and uneasy recognitions
Back in the lab, Koslov does not recognize her and another man named White claims to know her. During a campus lecture, a woman in the audience recognizes Sarah, confirming that others are aware of her under circumstances she does not grasp.
Where:Sleep lab and campus
- 9
Pursuit, evasion, and water intrusions
After evading the police outside her apartment, she hides in the laundry again as water starts to seep in, signaling that the boundary between dream and reality is breaking down. The tension suggests someone is manipulating her environment from afar.
Where:Outside apartment / Laundry room
- 10
Sleep lab revelation
She wakes in the sleep laboratory to learn that the police found she has been sleepwalking; she cannot recall the events, but data shows she was dreaming. White suggests that the stalker might help connect two conflicting realities, hinting at a sinister link between her waking life and dreams.
When:During monitoring session Where:Sleep lab
- 11
Diary reveals a shocking truth
Back home, Sarah reads a diary and discovers that Jonathan was murdered, not the suicide she believed. This revelation reframes her memories and deepens the mystery of who is manipulating her life. Cooper advises protection as the strain of memory returns.
Where:Apartment
- 12
Anna Wells and the mind's trap
The truth finally emerges: Sarah realizes she is actually Anna Wells, the obsessive fan who shot Jonathan, while the original Sarah Foster is the man’s true partner. Flashbacks reveal Anna's coma and her struggle for breath, trapped inside her mind as she mistook her identity.
Where:Mindscape / memory space
Who Are the Main Characters in Sleepwalker?
9 characters, among them Sarah Foster / Sarah Wells (Anna Wells), Warren Lambert and Dr. Scott White: who each one is and the part they play in the story. 8 of them link to the actor’s page.
-
Sarah Foster / Sarah Wells (Anna Wells)
Played by Ahna O'Reilly
College student whose sleepwalking and memory fragmentation pull her between competing identities. Her reality becomes unstable as she uncovers connections to a different life and past events surrounding Jonathan Grey.
- 🧠 Psychological
- 🔎 Mystery
-
Warren Lambert
Played by Haley Joel Osment
A determined stalker who weaponizes Sarah’s sleepwalking and memories, embodying the danger of obsession and control. His actions push the protagonist toward a startling truth about herself.
- 🔎 Obsession
- 🕷️ Stalker
-
Dr. Scott White
Played by Richard Armitage
Sleep-lab physician who interprets brain activity and dream data, offering guidance through the increasingly unstable reality. He emphasizes dreams as a pathway to emotional understanding.
- 🧠 Scientist
- 🔬 Medical
- DE
Dr. Elaine Cooper
Played by Izabella Scorupco
Professor who recognizes memory disruption and works to ground Sarah while clarifying what’s real. She serves as a stabilizing presence amid the mind-bending events.
- 🎓 Academic
- 🧠 Psychological
-
Dr. Koslov
Played by Kevin Zegers
Researcher monitoring Sarah’s brain activity, central to the dream-study dynamic that blurs the line between dreaming and waking life.
- 🧪 Researcher
- 🧠 Brain science
-
Dawn
Played by Rachel Melvin
Sarah’s roommate and friend figure who represents normalcy and stability, later highlighting how memory and identity can be destabilized by others.
- 👭 Friend
- 🧠 Memory
- N
Nichole
Played by Emma Fitzpatrick
Imposter roommate who disrupts Sarah’s sense of home, underscoring how identity and reality can be manipulated from within.
- 🕵️ Impostor
- 🔍 Mystery
- OD
Officer Dowden
Played by Adam O'Byrne
Police officer involved in investigating the stalking and broader mystery surrounding Sarah’s sleepwalking episodes.
- 👮 Authority
- 🕵️ Investigation
- AW
Anna Wells
The obsessive fan whose past actions are tied to the mystery; the narrative reveals a dangerous history that intersects with Sarah’s reality.
- 🧠 Identity
- 💥 Trauma
Where and When Is Sleepwalker Set?
Sleepwalker is set in University Campus, Sleep Clinic, Apartment, Laboratory and Strange House (Present day). Here is why the time and place matter to the story.
When
Present day
Set in modern times, Sleepwalker follows a college student navigating contemporary sleep research and memory issues. The plot relies on brain-monitoring tech, diary records, and campus life to drive the mystery. The blend of clinical settings with everyday student routines situates the events in a recognizable, current era.
Where
University Campus, Sleep Clinic, Apartment, Laboratory, Strange House
Most of the story unfolds on a university campus and within a sleep research clinic. The apartment serves as a recurring site where memories surface and reality frays. The laboratory environment provides a clinical backdrop that contrasts with the eerie, dream-driven episodes in other locations.
- 🗺️ College Campus
- 🧪 Sleep Clinic
- 🔬 Laboratory
- 🏠 Apartment
- 🏚️ Strange House
What Are the Themes of Sleepwalker?
3 ideas the story keeps returning to, among them Identity, Dreams & Reality and Obsession.
-
01
Identity
The protagonist’s sense of self fractures as she shifts between multiple identities—Sarah Foster, Sarah Wells, and Anna Wells. Conflicting documents, dreams, and memories challenge what she believes about who she is. The ultimate revelation ties her identity to a separate, dangerous history, forcing a confrontation with what memory really defines.
-
02
Dreams & Reality
Dream sequences and dream data increasingly steer the narrative, blurring the line between waking life and sleep. Medical interpretations of brain activity intersect with the protagonist’s evolving perceptions, making it hard to distinguish truth from illusion. The dream world becomes a battleground for emotional truth and self-understanding.
-
03
Obsession
A relentless stalker drives the tension, illustrating how fixation can erode safety and autonomy. The plot explores the dangers of fanatical devotion and how memory can be weaponized. Surveillance, manipulation, and memory intrusion reveal the destructive power of obsession.
What Kind of Film Is Sleepwalker?
Dark in tone, with steady pacing and a complex story, going by the plot summary.
- Tone
- Dark
- Pacing
- Steady
- Story
- Complex
- Intensity
- High
- Ending
- Sad
A disorienting and paranoid psychological thriller that traps the viewer in the protagonist's fractured reality, blurring the lines between dreams and memory with a consistently unnerving and anxious atmosphere.
- anxious
- paranoid
- dreamlike
- unsettling
- claustrophobic
- disorienting
- psychological thriller
- identity crisis
- memory loss
- sleep disorder
Content notes: suicide, murder, suffocation, stalking.
Quiz
How well do you remember Sleepwalker? Test yourself on the story.
Where to Watch Sleepwalker
Stream it on Amazon Prime Video and Fandango at Home Free, or rent or buy it from Amazon Video and Apple TV Store. US availability and prices from JustWatch.
Stream 7
Amazon Prime Video 
Amazon Prime Video with Ads 
Fandango at Home Free 
Hoopla 
Pluto TV 
The CW 
Tubi TV 
Streaming availability in the US, powered by 
