Elizabeth Parsons lives a seemingly picture-perfect life with her husband, Kevin, and their son, Joshua. Being a lonely child, Joshua begins having an imaginary friend called Z. Elizabeth is unconcerned at first, that is until Joshua gets suspended for his increasingly violent and disturbing behaviours at the elementary school. He blames all this on Z. To Elizabeth`s horror, she realises that Z is not imaginary after all and it is an evil entity that she must save her son from.