In the history of the cinema, the German director Veit Harlan occupies an especially ignominious position. It is his name that is attached to “Jew Süss,” perhaps the most notoriously anti-Semitic movie ever made, a box office success in Nazi Germany in 1940 that was so effective that it was made required viewing for all members of the SS.

But what motivated Harlan to write and direct such a film? Was he a Nazi true believer, an opportunistic careerist or just a filmmaker too fearful of retribution to say no to Joseph Goebbels, the Nazi propaganda chief? Those are some of the questions that another German director, Felix Moeller, asks in “Harlan: In the Shadow of Jew Süss,” a documentary that opens a two-week engagement Wednesday at Film Forum in Manhattan.

“Harlan may be forgotten, but he was an influential figure, frequently mentioned in Nazi documents and in Goebbels’s diary,” Mr. Moeller said. “That interested me as a historian, but I also wanted to know what the younger generation thinks of this. We think we know everything, but when you ask what your grandfather did on the Eastern Front, what went on in your own family, it’s a different matter, and that story is important to me.”

Mr. Moeller’s film includes some snippets from “Jew Süss,” whose commercial exhibition or sale as a DVD is still prohibited in Germany and several other European countries. Set in the 18th century, it claims to be a dramatization of the true story of how a sinister, cunning Jewish financier, Joseph Süss Oppenheimer, took control of the duchy of Wurttemberg while preying sexually on a pure Aryan maiden, played by Harlan’s wife, Kristina Söderbaum. The bulk of Mr. Moeller’s film, however, consists of interviews with descendants of Veit Harlan, forced to live with his surname and the stigma of “Jew Süss.”