Sleepwalker is a 2017 American mystery psychological thriller film directed by Elliott Lester, and starring Ahna O'Reilly.

Ever since her famous author husband, Jonathan Grey, committed suicide, college student Sarah Foster has suffered a sleep disorder involving sleepwalking.

In the sleep laboratory Dr. Koslov and Dr. Scott White explain her neural activity will be observed.

Sarah inquires at the library about selective memory loss, and learns that partial retrograde amnesia usually resolves on its own but if hallucinations develop, it might be psychosis.

Back in her apartment, Dawn is absent and a girl Sarah has never met named Nicole claims to live there as her roommate.

She spends the night in the apartment block laundry room closet and sees water seeping under the door.

He takes her back to his home, where he explains that when we dream, the rational part of our brain uses stories to make sense of emotions.

In the sleep lab, Koslov doesn’t recognize her and a completely different man introduces himself as White.

Sarah awakes in the sleep laboratory with the original White, who tells her the police found her sleepwalking.

White thinks the stalker might be an anchor connecting the two worlds and asks why her husband committed suicide.

On the library computer she finds a news report that Jonathan Gray was murdered by a fan.

Sarah returns to her apartment with the window intact, where the dark haired man springs out and tries to suffocate her.

Cooper assures White he’s doing the right thing, but she doesn’t know his patient and denies having met them earlier.

Sarah remembers her stalker’s name - Warren Lambert - and that he is obsessed with Jonathan’s books.

In a series of flashbacks Anna is gasping for breath in a coma bound to a hospital bed.

A male nurse who looks like the attacker caresses her face, gently telling her, “Don’t worry Anna.” Water from a ventilator drips on her foot.

[1] THe Hollywood Reporter said, "the willfully vague plot gradually unravels as inexorably as the protagonist’s perception of reality.