Having recently lost her fiancé, clinical psychologist Celeste DuPont decides to accept a staff position at New England’s Milburn Institute, a remote psychiatric facility for the criminally insane. Under the careful guidance of her mentor, Dr. Quilley, Celeste subscribes to his method of therapy, allowing the patients to consider themselves “guests” and letting each create a persona of their choice. But to her horror, Celeste learns that she has actually been committed to the facility as a patient and that she’s trapped in the institution. After several attempts to escape, strange visions and her relationship with Dr. Desmond Moore begin to make her doubt her own sanity. Celeste must now uncover the truth before she becomes a permanent guest.