There is no character named "Hamilton Nash" in the original novel (nor any other story by Dashiell Hammett). The detective hero of the novel is the unnamed "Continental Op" who features in many Hammett stories, and who is a slightly overweight man of below average height (about 5' 6"). James Coburn plays an operative of the Continental Detective agency, but there the resemblance ends. Coburn is made up to resemble the author Dashiell Hammett.
According to Michael Shonk at The Mystery File website, "THE DAIN CURSE originally appeared as four separate Continental Op stories in Black Mask magazine. [Dashiel] Hammett would rework the four stories ("Black Lives" November 1928, "The Hollow Temple" December 1928, "Black Honeymoon" January 1929 and "Black Riddle" February 1929) into a three-part novel (Knopf, 1929)".
A complete two-disc full-length version of the six hour mini-series is now available on DVD.
The production produced both a feature length cut and mini-series versions of the story. The mini-series was made first for television then a feature length cut was produced for home video.