At the end of the movie it is established that the woman is mentally ill .
Is in fact the serial killer on the loose , as woman cleans up the bodies and rearranges the furniture and proceeds to talk to woman 's mother using the disconnected telephone .
At the end of the movie it is established that the woman is mentally ill and is in fact the serial killer on the loose , as she cleans up the bodies and rearranges the furniture and proceeds to talk to her mother using the disconnected telephone .