Janet Wilson is a married attorney living in Erie, Pennsylvania, who's been having recurring nightmares about a man dressed in black burglarizing her home. The man in black whistles the nursery rhyme London Bridge is Falling Down as he carefully picks through her things. With loaded gun in hand, Janet startles him. He attacks her; she shoots him yet he crawls after her before he dies. But what truly frightens Janet is with each dream her attacker gets closer and closer until finally he touches her just before she awakens.
Her husband, Dr. Michael Wilson, a clinical psychiatrist, convinces her that this is just a dream until several strange occurrences begin taking place, distorting fantasy with reality. There are other things buried deep within Janet's memory of her childhood, such as who was the young woman with black hair? Why is Regina, her imaginary childhood friend, contacting her again after all of these years? What is the significance of the handheld mirror given to her a long time ago by her mother? As she struggles to find the answers the events that gradually unfold reveal that nothing is what it seems.