After writing a series of articles about a pedophilia scandal, journalist Ji Won receives threatening calls on her cellular and subsequently changes her number. Her close friend Ho Jung, who is infertile, and her husband Chang Hoon invite Ji Won to move to their empty house in Bang Bae that is newly furnished. When Ho Jung's daughter Yeong Ju answers an anonymous phone call on Ji Won's new cell phone, the girl screams and begins to show a disturbing attraction for her father and jealous rejection towards her mother. Meanwhile Ji Won receives more mysterious phone calls and sees a teenager playing Beethoven's "Moonlight Sonata" on the piano. After investigating her phone number, Ji Won discovers that the original owner of the number, Jin Hee, had vanished and that the two subsequent owners of the number had died mysteriously in unusual circumstances.