question: The mystery novel turned mystery horror film And Then There Were None to Island of Blood was written by whom?
answer: Agatha Christie
context: Title: The Unseen (novel)
  Passage: The Unseen is a 1990 horror/mystery novel written by Vermont author Joseph A. Citro.  The book examines mysterious goings-on in the middle of the wilderness of the Northeast Kingdom of Vermont.  A former journalist becomes curious after an area man kills himself having witnessed something horrific in the wilderness.  The story follows his efforts, as well as those of his girlfriend's son and his friend, to unravel the mystery.  The book's plot references several real New England folktales and occult events, including area sasquatch legends and a doomed hotel.  Initially, the book was to be titled "The Gore," not referring blood and guts but instead the peculiar areas of no man's land that litter Vermont.  Citro was not fond of the forced name-change, fearing that the novel would become like its namesake and barely be read.  Citro's prediction proved unfortunately to be correct, and the novel did not fare well.  In 2000, it was re-released under its original title by Hardscrabble Books and enjoyed greater success.  The next time the novel was redistributed it was under DS Publishing of Anchorage, Alaska.
  Title: And Then There Were None
  Passage: And Then There Were None is a mystery novel by English writer Agatha Christie, widely considered her masterpiece and described by her as the most difficult of her books to write.  It was first published in the United Kingdom by the Collins Crime Club on 6 November 1939, as Ten Little Niggers, after the British blackface song, which serves as a major plot point.  The US edition was not released until December 1939; its American reprints and adaptations were all retitled "And Then There Were None", after the last five words in the nursery rhyme "Ten Little Indians".
  Title: Island of Blood (1982 film)
  Passage: Island of Blood (also known as Whodunit?  and Scared Alive: Island of Blood) is a 1982 mystery horror film based (or borrowed) around "And Then There Were None" by Agatha Christie.
  Title: Pillow of Death
  Passage: Pillow of Death is a 1945 film noir mystery horror film directed by Wallace Fox and starring Lon Chaney, Jr. and Brenda Joyce.  The last of the Inner Sanctum mystery films, it is based on a story by Dwight V. Babcock.  The "Inner Sanctum" franchise originated with a popular radio series and all of the films star Lon Chaney, Jr.  It was the only entry in the series to dispense with the introduction by a disembodied head in a crystal ball, as well as the only one to feature comic-relief characters to alleviate the grim tone.
  Title: The Wicker Man
  Passage: The Wicker Man is a 1973 British mystery horror film directed by Robin Hardy.  It stars Edward Woodward, Britt Ekland, Diane Cilento, Ingrid Pitt, and Christopher Lee.  The screenplay by Anthony Shaffer, inspired by David Pinner's 1967 novel "Ritual", centres on the visit of Police Sergeant Neil Howie to the isolated island of Summerisle, in search of a missing girl.  Howie, a devout Christian, is appalled to find that the inhabitants of the island have abandoned Christianity and now practise a form of Celtic paganism.  Paul Giovanni composed the film score.
citations: Island of Blood (1982 film) And Then There Were None