Before director Joshua Oppenheimer's The Act of Killing hit theaters in the West, it would have been almost impossible to stop an American on the street and find someone who was even aware that more than a million people were killed by government and paramilitary forces in Indonesia during the mid-1960s. Now, you'd still be hard-pressed to find someone, but at least it is possible -- at least this dark, horrific secret feels more out there in the popular universe.

The Look of Silence is Oppenheimer's follow-up -- a companion piece on the Indonesian genocide that doesn't double back on The Act of Killing so much as it further plumbs its depths. The first film puts a bizarre, banal face on the perpetrators of evil. This one delves in to collective memory, hammering away at the rationalizations ad infinitum that underpin not just Indonesian society, but our own.

Oppenheimer's main character this time around is Adi, the middle-aged brother of a victim of the mass killings. Unlike most of his countrymen, perpetrators and victims of the atrocity alike, he will not yield to the past, even as it slips out of the conscience of so many around him. He functions as a captivating subject, but also as an investigative reporter during some of the film's most gripping moments.

Those moments come when Adi, often using his trade as an eye glass salesman as a point of entry, directly confronts the men responsible for his brother Ramli’s gruesome murder, and the family members who know only fractions of the truth. One after another, and usually in their home, Adi asks a probing question here and another one there, often using silence and his own confusion/bewilderment to draw out a mixture of justification and blame for the mass slaughter. No one is to blame for the massacres — the Army or the U.S. are offered up halfheartedly — according to these men. And, well, the past is the past. Why open up an old wound? It’s appalling stuff, just as much because it is a tradition as old as humanity itself as it is because there are particular faces and voices matched to such behavior.

Interspersed with these conversations are Adi’s interactions with his family — his adorable daughter, worried wife, crippled and senile father and, most notably, his mother, who paradoxically carries deep anger about the death of her son and, vocally at least, is resigned to the idea that this is all in the past. There are also multiple scenes in which Adi watches extensive footage of his brother’s killers, not only confessing to mass murder but also re-enacting the murders in the spot where they occurred. Anwar Congo is not the only person, apparently, who was willing to recount the vivid, gory details of the purges to Oppenheimer on camera. Most of the men captured on film will meet Adi in person. His gaze is constant as he watches — pensive, sad, frustrated. He had something taken from him, and during many moments of the film, it feels like he’s the only one who honors what he has lost, who won’t just wave it away with a “past-is-the-past” platitude.

The cumulative effect of all of this is devastating — like being plowed over by one of the military trucks Oppenheimer bookends the film with in slow motion. Setting aside how such behavior can go unpunished for five decades, it is infuriating to see Ramli’s grisly demise talked about so cavalierly in one moment then hear Adi be told to move on in the next.

Oppenheimer attempts to tie these events back the United States in two moments — first, with some eyeroll-worthy NBC News footage on the genocide from the 1960s and second, when one of the perpetrators says outright that America taught them to hate the “Communists” — the ostensible target of the purges, though rarely, it seems, the actual victims. I wouldn’t argue that there is no explicit link. Rather, I would claim that this tragedy and the subsequent maddening indifference to it is bigger than the very notion of America. Indeed, it has practical applications to historical events within our own borders — slavery, the near complete wipeout of the Indians, our treatment of various immigrant groups at different points in our history. These uncomfortable, inconvenient truths have been wiped away, discarded and marginalized so that progress is not impeded by self-doubt and self-examination.

It’s not wrong to argue that, at some point, we all have to move on. But moving on, as Adi so painfully illustrates, is quite a bit different than collective amnesia. Oppenheimer spends quite a lot of time on Adi’s father. He is blind, deaf and almost impossibly frail. When Adi asks how old he is, his reply is “16 or 17.” He is senile. He may have remembered the death of Ramli at some point, but he doesn’t anymore. Toward the very end of the film, Adi sits down with the family of one of his brother’s killers. The killer himself has recently passed away. When their father’s deeds are revealed, they seem troubled but simultaneously unwilling to dig deeper — to look around their house at their wealth and wonder. They can barely muster an apology on his behalf.

The generation that lived through the death of Ramli and so many others is dying off, and rapidly. With them will go the actual memory of what happened. Adi’s confusion and sense of injustice will remain for a few more decades. And then what?

The Look of Silence doesn’t offer an answer. It is frustrated that there isn’t a good one and demands that its audience acknowledge this fact and, just maybe, heads back out in to the world more aware, more willing to seek out the uncomfortable truths and to live with them instead of what is convenient. Unlike its predecessor, it is not as utterly unique a film. It is probably even guilty of belaboring its point. But this is one of those points worth belaboring. It’s too important for it not to sink in fully.