Patricia Highsmith (January 19, 1921 – February 4, 1995) was an American novelist and short story writer, known for her psychological thrillers, which led to more than two dozen film adaptations.
 Her first novel, "Strangers on a Train", has been adapted for stage and screen numerous times, notably by Alfred Hitchcock in 1951.
 Highsmith wrote 22 novels, including her series of five novels with Tom Ripley as protagonist, and many short stories.
 Existentialism is the literary movement that most influenced her writing, with "Dostoyevsky and Gide through Camus and Sartre" among her favorite authors.
 Graham Greene described Highsmith as "the poet of apprehension rather than fear.
 Fear after a time...is narcotic, it can lull one by fatigue into sleep, but apprehension nags at the nerves gently and inescapably."
 Published under the pseudonym of "Claire Morgan," Highsmith wrote the first lesbian novel with a happy ending, "The Price of Salt", republished 38 years later as "Carol" under her own name.
Ian Wolfe (November 4, 1896 – January 23, 1992) was an American actor with around 400 film and television roles.
 Until 1934, he worked in the theatre.
 That year, he also turned to film and later television, as a character actor.
 His career lasted many decades and included many classics; his last screen credit was in 1990.
The Price of Salt (later republished under the title Carol) is a 1952 romance novel by Patricia Highsmith, first published under the pseudonym "Claire Morgan".
 Highsmith—known as a suspense writer based on her psychological thriller "Strangers on a Train"—used an alias because she did not want to be tagged as "a lesbian-book writer", and because of the use of her own life references for characters and occurrences in the story.
 Though Highsmith had many sexual and romantic relationships with women and wrote over 22 novels and numerous short stories, "The Price of Salt" is her only novel about an unequivocal lesbian relationship and its relatively happy ending was unprecedented in lesbian literature.
 It is also notable for being the only one of her novels with not only "a conventional 'happy ending but in which her characters also had "more explicit sexual existences".
John Forsythe (born either John Lincoln Freund or Jacob Lincoln Freund; January 29, 1918 – April 1, 2010) was an American stage, film/television actor, producer, narrator, drama teacher and philanthropist whose career spanned six decades.
 He also appeared as a guest on several talk and variety shows and as a panelist on numerous game shows.
Checkmate (1930) is one of the many popular novels written by Englishman Sydney Horler in the first half of the 20th century.
 Forgotten today, the book describes the exciting lifestyle of the wealthy social elite.
 "Checkmate" adds an element of crime and adventure to that atmosphere, but the countless coincidences throughout the plot guarantee a thoroughly predictable happy ending, complete with a double wedding.
Aleksey Burago (Director) graduated from Moscow Academy of Theatre Arts (GITIS) and studied with world famous theater director Pyotr Fomenko.
 His Moscow directing credits include: "Beyond Recognition."
 Off-Broadway, he has directed "Gamblers," "An Absolutely Happy Village", "Ah!
 My Dear Andersen" and "On the Eve."
 At HB Playwrights Foundation, he has directed "Vassa," "Picnic on the Battlefield," "The Master and Margarita," "Wonder Bread" and "Lady with the Lapdog with Jokes and a Happy Ending."
 His TV credits include "The Queen of Spades" (Actor/Director).
 His awards include 1992 Best Director - St. Petersburg Comedy Festival and 1993 Best Director - Moscow Annual Festival of Classical Plays.
 He has been on faculty at Theatre Academy and Conservatory in St. Petersburg, Danish Theatre School GITIS and Manhattanville College, where he taught acting and staged the short stories of Anton Chekhov.
 The Artistic and Founding Director of The Russian Arts Theater & Studio, Aleksey Burago is now based in New York City.
 He is an Associate Member of SSDC and also Director-in-Residence at Bilkent University in Ankara, Turkey.
The Happy Ending is a 1969 drama film written and directed by Richard Brooks, which tells the story of a repressed housewife who longs for liberation from her husband and daughter.
 It stars Jean Simmons (who received an Oscar nomination), John Forsythe, Shirley Jones, Lloyd Bridges and Teresa Wright.
Ah, Wilderness!
 is a comedy by American playwright Eugene O'Neill that premiered on Broadway at the Guild Theatre on October 2, 1933.
 It differs from a typical O'Neill play in its happy ending for the central character, and depiction of a happy family in turn of the century America.
 It is O'Neill's only well-known comedy.
Karen Sheila Gillan (born 28 November 1987) is a Scottish actress, director, and screenwriter.
 She is known for the role of Amy Pond, companion to the Eleventh Doctor, in the BBC science fiction series "Doctor Who" (2010–13).
 In film, she has starred as Jane Lockhart in "Not Another Happy Ending" (2013), Kaylie Russell in the horror film "Oculus" (2013), and Nebula in the Marvel film "Guardians of the Galaxy" (2014) and its sequel "Guardians of the Galaxy Vol.
 2" (2017).
 She took part in the upcoming films "" (2017), "" (2018) and its untitled sequel (2019).
 In 2017, she wrote and directed her first feature film, "The Party's Just Beginning".
Elizabeth Savage (née Fitzgerald 15 February 1918 – 15 July 1989) was an American novelist and short-story writer.
 In nine novels, she explored the turbulent decades between 1930 and 1980 in the Western United States and along the Atlantic Coast.
 Her work focuses on men and women dealing with the Great Depression, World War II, the birth of the women’s movement, the Sixties counterculture and the Vietnam War.
 Among her best-known books are "The Last Night at the Ritz", the semi-autobiographical "The Girls from the Five Great Valleys", "Summer of Pride", "But Not for Love", "A Fall of Angels", and "Happy Ending".

Question: How many decades did the career of the American actor, who starred in "The Happy Ending," span?
Answer: six