Even at their most monstrous, some famous Nazis still seem recognizably pathetic. You can joke about them. You shouldn’t, but you can. Then there’s Josef Mengele. The memory of him seems permanently terrifying. Mengele was the SS physician, a sort of anti-Hippocrates, who tortured Auschwitz prisoners in the name of research, and got away with it by fleeing to Argentina after the war. Writer-director Lucía Puenzo’s film finds him there, in Patagonia in 1960, as a mysterious stranger (Alex Brendemühl) befriending a poised but physically underdeveloped 12-year-old girl (Florencia Bado) and ingratiating himself into her family. The girl’s mother (Natalia Oreiro) seems amenable to the doctor’s ideas for treatment, perhaps because she herself is a product of German schooling. As it happens, she’s also pregnant with twins — of special interest to Mengele, who liked, as one character puts it, “using one baby as a control and experimenting on the other.” Meanwhile, her husband (Diego Peretti), who makes porcelain dolls by hand as a hobby, seems more suspicious of the whole situation, at least until he becomes distracted by the doctor setting him up with a full-blown doll factory. Okay. So. What could possibly go wrong? Better question: See how even with the insulation of a half-century’s retrospect, jokes can’t fully disarm the dread here? Mobilizing a fine array of camera-commanding faces, Puenzo’s best move is to avoid playing this as a horror movie. Instead, it’s just a deeply ominous slice of life.