After witnessing a traumatic and inexplicable incident involving a patient who violently takes her own life, Dr. Rose Cotter, a psychiatrist, begins experiencing frightening occurrences that she cannot explain. The patient had come to Dr. Cotter, terrified and claiming to have witnessed something supernatural that wouldn't leave her alone - a recurring motif of a haunting, ominous smile. Shaken by what she has seen, Rose tries to push it aside and return to her normal routine. However, it soon becomes apparent that the sinister force that tormented her patient has now latched onto her.

As the terrifying events escalate, Rose finds herself being plunged into a nightmarish reality in which she is stalked by an unknown entity that others can't see. Desperate for answers, she dives into a frantic investigation that leads her to uncover a pattern of similar cases throughout history. With an increasingly distorted sense of reality and time running out, Rose must confront her past and untangle the mystery if she hopes to escape the horrific fate that seems to have befallen her.