In the movie there is a girl who is in a mental hospital and when she gets to come her father is remarried and she is playing like her mother is still alive and her sister is too and is posing that her step mother is a killer but her sister and mother were dead prior to her going to the mental hospital that's why she had to go to the mental hospital. Her mom was sick and the nanny was who the dad ended up marrying and the mother and sister died in a house fire at a house they had by the lake in their backyard. At the end she is telling the story to another girl in the mental hospital.

The Uninvited (http://www.imdb.com/title/tt0815245/)