Very active on the Broadway stage, Duncan came to films just before the coming of sound, most memorably in vamp roles. She made films for such important directors as Frank Borzage and F.W Murnau (in the lyrical romances, "The River" 1929 and "City Girl" 1930 and as a particularly alluring temptress in "Four Devils" 1929). She also played a leading role in the "Rashomon"-like early talkie, "Thru Different Eyes" (1929), as a man's murder is recounted from various suspects' points of view. By the early 1930s Duncan was playing supporting roles in films as, for example, one of the women terrorized by vengeful half-caste Myrna Loy in the bizarre melodrama, "Thirteen Woman" (1932). Duncan's last role was, ironically, in Oscar-winning upstart Katharine Hepburn's third film, "Morning Glory" (1933), as the star whom Hepburn replaces. Duncan retired from acting to marry into the Palm Beach horsey set and became an influential society figure.