A young woman living alone moves into Apartment 306, only to find herself trapped in a series of nightmares—the disappearance of the previous tenant, strangely moving objects, footsteps by her bed at night, and a diary filled with terrifying entries left behind. The seemingly helpful apartment manager harbors sinister intentions, and her gentle and refined boss sets a trap to ensnare her. Both are intimately connected to a series of murders and missing girls. When the locks can no longer keep out prying eyes, and kindness hides deadly traps, she must fight for her life amidst a hunt driven by desire and malice, and uncover the double crimes of the apartment and the two men.