Poco? Mucho.

"The screenplay for director Jacques Tourneur's classic "Out of the Past" (1947) was worked on by three different writers before reaching its final form. Daniel Mainwaring, who wrote the film's source novel under the pseudonym Geoffrey Homes, was the first to complete a draft of the screenplay. His draft sticks closely to the novel, maintaining the cliched toughness of its tone. James M. Cain, called in to rewrite Mainwaring's version, added several plot elements and a happy ending, all of which were discarded. Cain's second draft introduced the two-part structure that the film would ultimately employ -- the first part consisting of a flashback about the hero's past and the second part continuing in the present. The final draft was by Frank Fenton, who contributed most of the film's best dialogue and many key plot elements and who rounded out the characters. Unfortunately, Fenton received no screen credit."

(c) Schwager, Jeff. "The Past Rewritten," Film Comment, V. 27 Jan/Feb. 1991, pp. 21-23.