Ghost Story - Season 1 Episode 7 Half a Death

Christina is a young woman with a twin sister, Lisa, whom she has never met. She hopes to meet Lisa on a visit home but is distressed to find out that Lisa has recently died. Christina begins to hear Lisa calling her at night and then starts to have visions of Lisa in an open grave. She tells her mother about this and discovers some unpleasant family secrets about Lisa. Does Lisa want revenge...or does she simply miss the sister she never had?