Rebecca (Teresa Palmer) left her mother Sophie (Maria Bello) early and lived alone. Later, Sophie married Paul (Billy Burke), and Rebecca had a half-brother named Martin (Gabriel Bateman). However, Paul died in an accident, and Sophie fell into sadness and despair. At the same time, Martin found that his mother often whispered to the dark, as if there was an "uninvited guest" hidden there. Martin, who was mentally tortured, asked Rebecca for help, and Rebecca remembered a very similar incident in her childhood. After investigation, it is found that the mysterious figure hidden in the darkness is named Diana (Alicia Vela-Bailey). She was her mother's best friend during her hospitalization, and later died in a medical accident. Now, Diana's ghost has returned to Sophie again. She wants her best friend to be with her forever, and anyone who attempts to approach will face the threat of death.