Andre Singer’s “Night Will Fall,” debuting on HBO on Monday, tells the story of what happened to producer Sidney Bernstein and director Alfred Hitchcock’s hundreds of thousands of hours of footage of the liberation of the Nazi concentration camps.

Vivid, chilling and horrific, the images were part of an Allied-commissioned project in 1945 to counter any claims that the Holocaust didn’t happen. As Singer tells Variety‘s “PopPolitics” on SiriusXM, the documentary film was to show the German people “their guilt to what had happened to them during the war and that happened in the camps.”

Bernstein, who was overseeing the project for the Allies, enlisted Hitchcock for his input on the finished work, which was simply to be called “German Concentration Camps Factual Survey.” But by the summer of 1945, U.S. and British military officials dropped the project. Although director Billy Wilder edited some of the film into a project called “Death Mills,” it was not until 1984 that the complete footage was found by scholars. It was only recently restored by the Imperial War Museum.

“In a way, there was no excuse for the material not to be used as it was intended,” Singer says. But after the victory in Europe, the Allies faced a new enemy, the Soviet Union, and the concern was that “perhaps it was not a good time” to show such footage when the U.S. and Britain wanted to bolster western Germany.

“I don’t think there was a conspiracy to suppress the new film,” Singer says. “It was just the time was wrong and things were changing so fast in Europe at that time.”

“Night Will Fall” is tied to the 70th anniversary of the liberation of the camps, and features interviews with survivors, as well as soldiers and cameramen.

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Hitchcock was not the director on the project, but made a significant contribution: ensuring that the edits contained lengthy, one-take shots that panned across the landscape from nearby villagers to the camps. Along with map illustrations, the idea was to show how close the camps were to nearby towns and cities.

“It was effective,” Singer says. “I don’t think it would have happened without Alfred Hitchcock pushing it at that particular time.”

Hitchcock would later use the concept of lengthy, one-take shots in the movie “Rope.”

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On The Mix, U.S. News’ Nikki Schwab and Variety‘s David Cohen talk about why so much of the debate over the movie “American Sniper” is misguided, and they look ahead to an upcoming movie sure to stir partisan reaction, Michael Bay’s Benghazi project.

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Elizabeth Wurtzel, author of “Creatocracy: How the Constitution Invented Hollywood,” talks about how the Founding Fathers had the foresight to include a copyright clause in the Constitution, and why, perhaps even more than the First Amendment, it helped form the foundation for mass entertainment.

Nevertheless, as copyright faces new challenges from rampant piracy, she’s skeptical that much can be done to win the hearts and minds of the digital generation, in which the industry is battling a culture of free.

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Variety’s “PopPolitics,” hosted by Ted Johnson, airs on Thursdays at 2 p.m. ET on SiriusXM POTUS Channel 124.