Question: The mystery novel turned mystery horror film And Then There Were None to Island of Blood was written by whom?

Context articles: And Then There Were None
Island of Blood (1982 film)
The Unseen (novel)
J. A. Jance
House of Mystery (1934 film)
The Dead Talk Back
The Wicker Man
The Decagon House Murders
Pillow of Death
Rim of the Pit

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".
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.
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.
Judith Ann (J. A.) Jance (born October 27, 1944) is an American author of mystery and horror novels.
 She writes at least three series of novels, centering on retired Seattle Police Department Detective J. P. Beaumont, Arizona County Sheriff Joanna Brady, and former Los Angeles news anchor turned mystery solver Ali Reynolds.
 The Beaumont and Brady series intersect in the novel "Partner in Crime", which is both the 16th Beaumount mystery and the 10th Brady mystery.
 They intersect again in "Fire and Ice".
House of Mystery is a 1934 American Pre-Code mystery horror film directed by William Nigh.
The Dead Talk Back is a crime/mystery horror film that, while filmed in 1957, was never shown theatrically anywhere until it was unearthed in a warehouse find and distributed on video by Sinister Cinema in 1993.
 It was featured in a 1994 episode of movie-mocking television series "Mystery Science Theater 3000".
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.
The Decagon House Murders is a 1987 Japanese mystery novel and was the debut work of author Yukito Ayatsuji.
 Borrowing its basic plot structure from Agatha Christie's "And Then There Were None" (Christie's book is directly referenced by some of the characters at several points), it tells the story of a group of seven university students who travel to a deserted island that was the scene of a grisly mass murder six months earlier, where events soon turn ominous.
 "The Decagon House Murders" belongs to the honkaku subgenre of mystery fiction.
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.
Rim of the Pit (1944) is a locked-room mystery novel written by Hake Talbot, a pen name of Henning Nelms.
 Nelms, as Talbot, published one other mystery novel as well as two short stories.