Arnon Goldfinger, The Flat, 2011, color, 97 minutes. Arnon Goldfinger and Edda von Mildenstein.

ONE OF THE MOST SURPRISING, engaging, and psychologically complex documentaries of recent years, Arnon Goldfinger’s The Flat is a Holocaust movie like no other. It is also a mystery story, in which the moviemaker is a detective who follows clues, camera in hand, traveling back and forth between Israel and Germany, tracing the mind-boggling connection between his German-Jewish maternal grandparents and a high-level SS officer and his wife, a friendship that began before the Holocaust and continued long after.

The film opens just after the death of the moviemaker’s ninety-eight-year-old grandmother, Gerda Tuchler. Three generations of relatives informally assemble at the Tel Aviv flat where she and her husband lived for decades. The Tuchlers moved to Palestine in 1936 but they never identified as Israeli. Goldfinger remarks that visiting his grandparents’ apartment was like going to Berlin. At first The Flat seems as casual as a home movie, the family going through Gerda’s closets as they never would have dared when she was alive, wondering aloud how one woman could accumulate hundreds of pairs of gloves and handbags, anguishing about bundling a lifetime’s possessions into garbage bags and hurling them into dumpsters or selling the furniture and household goods for pennies. And then, while going through some papers, Goldfinger finds a copy of a Nazi newspaper from the mid-1930s; on the cover is a story about an SS officer and his wife touring Palestine with a German-Jewish couple. Why did his grandparents keep such a loathsome object? It is here that his nearly five-year investigation begins.

The film is couched almost entirely in the present tense. We are with Goldfinger as he, accompanied by a singularly unobtrusive camera operator, visits family members and people he has never met in an attempt to unravel the mystery of a relationship that obsesses him because it is all but unthinkable, and which was never discussed by those who knew something about it but pretended, even to themselves, that they didn’t. This is a movie about many shades of repression and denial, in which the movement of eyes and lips reveals as much as words do. Goldfinger is a superb interviewer. He gives his subjects all the time they want to respond to his questions, and, however reluctantly, they always give something away. His need to know motors every encounter and the movie in its entirety. Eventually, The Flat focuses emotionally on the conflict between Goldfinger and his mother, between his desire to ferret out family secrets and her reluctance to engage with her own history. Personal truth and historical truth become one and the same. The Flat is a great detective story, not only because it brings what has been hidden into the light, but also because the moral issues involved in Goldfinger’s pursuit can never be completely resolved.

Amy Taubin

The Flat opens Friday, October 19th in New York at the IFC Center and Lincoln Plaza Cinema.