For long stretches of Joshua Oppenheimer’s documentary “The Look of Silence,” we watch a man watching a movie. With a subtly pained expression, Adi Rukun of Indonesia concentrates on footage of his countrymen gleefully describing how they butchered countless people during that country’s anti-Communist purges of 1965 and 1966.

It’s an excruciating spectacle, especially considering that Adi’s brother, Ramli, was one of the victims.

“The Look of Silence” is Oppenheimer’s second movie about Indonesia’s bloody past, following “The Act of Killing” which earned the director a 2014 Academy Award nomination. That movie had a surreal, conceptual feel: Men who participated in the death squads, now elderly, agreed to reenact their gruesome deeds. They were only too happy to do it, considering they see themselves as heroes. Some still hold high government offices.

“The Look of Silence” doesn’t have a brilliant gimmick, but it’s a more profoundly shattering movie. Oppenheimer observes one man’s attempt to understand his family’s loss. Adi was born two years after Ramli was killed in 1965, and he lives with his wife, children and elderly parents. As is often the case in the aftermath of political killings, the family lives among the murderers in a forced harmony that relies on a tacit agreement never to dredge up the past.

But Adi has an idea. He’s an optometrist, who travels to people’s homes and fits them with glasses, which gives him the perfect opportunity to meet the men who killed his brother. When he does, he asks them probing questions that tend to make them either nervous or irate. But they give him answers, if only because he often refuses to leave. He sits patiently through uncomfortable silences until the killers talk about how they don’t have regrets; how they used to drink the blood of their victims in order to ward off insanity; and how there’s no reason the terror couldn’t happen again — especially to someone who asks too many questions.

Joshua Oppenheimer directed "The Look of Silence," a documentary about the Indonesian killings in 1965. (Drafthouse Films)

When Adi isn’t risking his life, he helps take care of his emaciated father, who has lost his sight, most of his hearing and nearly all of his mental faculties. These scenes cement Adi’s status as a gentle soul, supported by the fact that when he confronts murderers, he does it more from a place of curiosity than accusation. He doesn’t want revenge. He’s looking for something that turns out to be more heartbreaking. After watching one of Oppenheimer’s clips of killers joyfully revisting their crimes, Adi tries to rationalize the men’s ecstasy. Maybe they were boasting in order to overcompensate for extreme feelings of guilt, he posits.

He just wants to forgive them — if only they’d show some remorse.

“The Look of Silence” is as beautiful as it is bleak. There are long shots of quiet landscapes and extended close-ups of butterfly larvae trembling on the floor, preparing to break open. These moments of peace are juxtaposed with Adi’s tense, impromptu interviews and footage of Adi’s father, looking disoriented and frantic, as he crawls around his house, unable to understand where he is. “The Look of Silence” stitches together these disparate scenes, creating a powerfully lyrical whole. The world it conjures up may look calm, but its horrors are never far away.

PG-13. At Landmark’s E Street Cinema. Contains disturbing graphic descriptions of atrocity. 103 minutes.