Three years ago, Klaus Müller, the U.S. Holocaust Memorial Museum's chief expert on and investigator of gay issues, approached Epstein and Friedman at the Amsterdam premiere of "The Celluloid Closet" and pitched them an idea for a movie. The result is the gravely beautiful "Paragraph 175." The team's healthy respect for the variety of ways people respond to historical phenomena energizes this chronicle of what Richard Plant, in his groundbreaking 1986 book "The Pink Triangle," calls "The Nazi War Against Homosexuality."

Paragraph 175 was the section of the German penal code that in 1871 forbade homosexual contact between men. The original law read, "An unnatural sex act between persons of male sex or by humans with animals is punishable by imprisonment; the loss of civil rights might also be imposed." It predated the Nazis and outlasted them, and was not stricken from the books until 1969.

But it was the Nazis who strengthened and brutally enforced the paragraph. Convicted men were either sentenced to prison or sent to concentration camps (sometimes thrown into prison and then into camps), where they wore the pink triangle. Although Nazis did not round up gays as single-mindedly as they did Jews or Gypsies, only a third of the gays who were interred in camps survived. The other inmate groups tended to shun them, and the Nazis often subjected them to pseudo-medical experiments. Fewer than 10 are alive today. The filmmakers talk to six of them. (Plant estimates that from 50,000 to 63,000 homosexuals were detained in the Nazi years and that from 5,000 to 15,000 died in camps; the film puts those numbers, respectively, at 100,000 and 10,000 to 15,000.)

Epstein and Friedman's film is neither an apocalyptic horror movie nor a dirge. It probes how history can turn on a dime -- or a single paragraph.

Nothing is simple in "Paragraph 175." The filmmakers remind us that when homosexual Ernst Röhm headed that rabid Nazi unit the S.A., Hitler declined to denounce Röhm's personal behavior, which led anti-Nazis to paint the National Socialist Party as a homosexual hotbed. After Röhm and the S.A. fell in the Night of the Long Knives, Heinrich Himmler, the head of his own elite guard, the S.S., put a campaign of homophobia into brutal full swing. But by then -- when it came to gays -- the propaganda battle line had become hopelessly confused.

Even after the war, vital testimony to Nazi atrocities was silenced because homosexuality remained illegal in Germany for another quarter-century. The film reflects how difficult it is for men to testify to Himmler's reign of terror even now. One camp veteran in Poland and one in Germany refused to talk to the filmmakers. One survivor interviewed for the movie declines to summon up harsh memories, while another is still so apoplectic he can barely articulate his rage.

Yet another blithely talks about joining the German army after he emerged from prison, so he could still be among men. Lucid and involving, "Paragraph 175" draws you into its complexities and haunts you for days afterward with its mixtures of courage, compromise and frailty. It premieres theatrically in New York and San Francisco in mid-September. I spoke to Epstein and Friedman two weeks ago at their San Francisco office.

Your office is a block and a half from the San Francisco Public Library. Just now, when I went there and typed into the computer, "Gays and the Holocaust," it asked me to reword my search; I tried "Gays and the Nazis" and "Gays and the Third Reich" and "Gays and Germany," but the computer couldn't locate any book on the subject. This film must have differed from your others in requiring more pure historical research -- you weren't documenting or interpreting already well-reported events.

Epstein: When Klaus Müller presented us with his research it was an opportunity that we couldn't pass up. He had witnesses we could interview. But the big difference between this film and some of the other ones we've done isn't that we were discovering the history of this subject as we went along. The biggest difference is that it had a history that couldn't be presented or told in black-and-white terms -- contrary to what we naively may have thought before. It became much more confusing.

What did you think the story was before you actually got into it?

Epstein: You know: the classic story of victims and victimizers. Just as you couldn't find anything in the library, what we found was almost all mythology. We had to figure out what was real and what was myth.

Friedman: On one side, there was the mythology that there was a gay Holocaust. On the other side was the mythology of the gay Nazi. Both of those were wild extrapolations based on a grain of truth. There was no gay Holocaust. There was persecution of gay people. But there was no systematic annihilation and there was never any clear policy about homosexuals except that, from the time of the Röhm putsch on, homosexuality was contrary to Nazi ideology. And Röhm was the basis of the myth of the gay Nazi.

So, in terms of well-known movies, you have "Bent" on one side, for the myth of the gay Holocaust, and "The Damned" on the other, tying homosexuality itself to Nazism.

Epstein: Exactly. We tried to use "The Damned" to make that point, but that film didn't make it into our film.

Friedman: As we started to talk to these guys, we had to deal with our own feelings about being Jews and going to Germany and talking to Germans of that generation. They had a really different experience of that time than we're used to hearing. Some of them made you uncomfortable. Some of them made you wonder whether they were very nice people.

Epstein: In fact, they may have been "nice people" and may also have been sympathetic to national socialism. One guy who is in the film did say to us in the pre-interview, "All would have been fine, but for the fact that I was homosexual." Which sent chills up my spine.

At one point, this dapper character named Albrecht recalls volunteering for the German army after being released from prison. We hear one of you gasp, "Whu -- Why did -- Why?"

Friedman: That's Rob.

It is a freak-out for the audience as well, because he is a charming guy. But in order to understand him, you have to take this step you didn't think you'd have to take.

Epstein: That's what I mean. As filmmakers who try to engage an audience's sympathies, we tend to be drawn toward sympathetic characters. Here, all that was clear from the beginning was that we were dealing with gray areas.

Friedman: I think they're all sympathetic characters, but they contain a lot of contradictions. The film got interesting for me when these problems started to arise. It also got scary because we weren't sure how we were going to deal with them.

Now playing: Read all the recent movie reviews by Salon's critics