Ji-won, played by the popular Korean actress Kim Ha-Neul (My Tutor Friend, The Duelist, and the hit Korean TV show Damo) is a bright young student, but something happened to her that left her with a blank memory. She has very little recollection of who she is or her life before the incident. When her old friends mysteriously start dying one by one, she begins to investigate. As she slowly starts to piece together fragments of her past, strange and terrifying visions begin to haunt her. She discovers that she was once friends with three other girls, and together they formed an impenetrable alliance. Now as more friends continue to die, she draws nearer to discovering the mystery that connects the present to a dark and horrifying past.