Both a historical document and a warning about the caution with which such material has to be treated, Yael Hersonski’s remarkable “A Film Unfinished” provides not only the complete footage taken by a Nazi film crew in the Warsaw Ghetto in 1942 and discovered after the war, but also outtakes found as recently as 1998. To these Hersonski adds commentary from three survivors of the ghetto, excerpts from the contemporary diaries (including one kept by the Jewish “mayor” of the enclave), memoranda issued by the German district commandant, and recreations of the testimony of Willy Wist, one of the German cameramen whose identity was uncovered in 1962, about the process of filming. The result is a searing expose of the brutality of the Nazi regime ironically made by the perpetrators themselves, and a subtle examination of the process and purpose that lay behind it.

To fully understand the importance of the documentary, it has to be remembered that much of the footage of what’s often referred to as “The Ghetto” was taken to be a truthful picture of the conditions in which Jews lived in Warsaw, awaiting—though they didn’t realize it—transport to the death camps. But the written and oral testimony adduced here emphasizes that what’s portrayed in the footage is basically a sham. The scenes showing the pleasant, “normal” lives led by the more well-to-do residents would have aroused suspicion even in the absence of the observations about them, but what the outtakes prove is that even many of the sequences showing the poor suffering in squalor were staged, going through several “takes” to get them right.

Why was the footage taken in the first place? Even Wist can’t say for certain, but his comment that the motive was certainly propagandistic and his recollection that the team seemed to concentrate on the sharp line of demarcation between rich and poor in the ghetto suggest that the makers’ original idea was to show how Jews are accustomed to treat even their own disadvantaged brethren badly—proving that they are evil and parasitic by nature (and thus justifying their persecution). But if that was the motive, it seems that they realized the impossibility of fashioning an effective propaganda piece from the footage they shot and so abandoned the project, leaving the celluloid to lie forgotten in its canister.

For historians of the Nazi era, and the Holocaust in particular, “A Film Unfinished” naturally provides a wealth of material to work with. For scholars of cinema and researchers into the art of propaganda it should be an equally valuable tool.

But more broadly, it touches on basic epistemological issues about the value of any kind of historical evidence to our ultimate ability to achieve certain knowledge of the past. And, it should be noted, about itself. The way in which Hersonski has put together his film, carefully structuring it to raise precisely the questions he wants us to consider, carefully choosing the juxtapositions of text and image and even using dramatic recreations (the tapping keys of the commandant’s typewriter, the interrogation of Wist with tape recorder running) necessarily compels us to think about the character of his film, too. How manipulative is it? How accurate? How authentic?

The result is a documentary with many implications and layers of meaning, one that’s fascinating enough on the surface but even more so when you dig deeper beneath it.