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As a high school student in the 1990s, Lucia Puenzo was fascinated and mystified by an open secret: Hundreds of Nazi war criminals found refuge in her native Argentina.

Lucia Puenzo photo/laura ortego

“I was intrigued that so many families knew what was going on because they had a German man on their block or somewhere in their neighborhood,” recalls the acclaimed novelist and filmmaker. “Maybe they didn’t know so much in the ’60s and ’70s, but by the ’80s or ’90s everybody knew. How could they not open their mouths and say what happened? It had a lot of echoes of our military coup d’etat, where so many Argentine families didn’t speak out.”

In her 2011 novel, “Wakolda,” Puenzo explored the devious machinations of a German doctor in the Patagonian town of Bariloche circa 1960 who befriends a young girl. The erstwhile physician injects her with growth hormones before turning his attention to her pregnant mother, distracting the suspicious father with a plan to mass-market his handmade dolls.

Puenzo adapted the novel for the screen, shifting the point of view from the maniacal doctor to the observant child. “The German Doctor,” which swept Argentina’s major film awards and was the country’s official submission for last year’s Oscar for best foreign language film, is a creepy, precisely crafted thriller made more unsettling by its restraint.

“The German Doctor,” which screened last fall in the Mill Valley Film Festival, opens Friday, April 25, in San Francisco and Berkeley.

At 37, Puenzo has already published five widely translated novels and directed three singular films including “XXY,” her prize-winning tale of an intersex teenager. Smart and fearless, Puenzo is attracted to subjects that others find off-limits or taboo — like the Nazi presence in Argentina.

Eva with her dollmaker father, Enzo, in “The German Doctor” photo/samuel goldwyn films

“For me, the big mystery has always been why this subject, that could be a hundred films and a hundred novels, has never been taken to film before,” she explains by phone from Europe, where she is doing a publicity tour. “We have maybe a few excellent documentaries on the subject but not one fiction film, and maybe we have five or six novels and that’s all, speaking about the subject.”

“The German Doctor” did solid box office in Argentina, which Puenzo sees as confirmation of pent-up interest. The film has been released in some 30 countries, including every European nation — except Germany.

The film succinctly illustrates how a cautious physician whom adults would view with suspicion — let’s call him Mengele — could win a child’s trust.

“In the camps there were so many horrible testimonies of how kids would call him Uncle Mengele; he would have sweets to give to the children and then he would take them to his experiments,” Puenzo says.

“The German Doctor” captures that deviousness and single-mindedness, while persuasively depicting the polite veneer Mengele devised to mask his lunacy and fool people.

“After the war, after the concentration camps, he disguised himself as this very civilized, seductive, enchanting man that lived for decades in three countries of Latin America without anybody suspecting who he was,” Puenzo says. “I think that’s how you have to portray this very sociopathic, complex personality who disguised himself. He was not the stereotype of the bad guy whom you could see coming.”

Puenzo comes across as earnest and serious but, befitting someone with a master’s degree in literature and critical theory, she recognizes the relationship between pop culture and popular perceptions of history.

“I remember films like ‘The Boys of Brazil,’ ” she says. “I loved it in a way, it’s such a strange film, but at the same time it’s a stereotype of Mengele. I think to honor these most horrific monsters you really have to show them in all their complexity. They were much more dangerous than we think.”

“The German Doctor” opens Friday, April 25, at Embarcadero Center Cinema in S.F. and Landmark Shattuck in Berkeley. In Spanish and German with English subtitles. (Rated PG-13 for thematic material and brief nudity. 93 minutes)