In a world bent on looking only at the future, filmmaker Joshua Oppenheimer weaves his documentaries from memories and lives that are long gone. He astonished the film world in 2012 with his Oscar-nominated documentary "The Act of Killing," whose central character, Anwar Congo, was a death-squad leader during Indonesia's communist purge of 1965-66. At Oppenheimer's request, Congo reenacted the process of arrest, torture and mass murder of his many victims. Friends from his former paramilitary unit followed suit, and Oppenheimer gave them the option of further reenacting their executions in whatever cinematic styles they desired — he shows them producing an ostentatious musical and a classic Hollywood-style noir film. The resulting footage was more grotesque, absurd and explosively violent than anything a fictional movie could have conjured.

Now Oppenheimer gives us "The Look of Silence," a companion piece to "The Act of Killing" — both were shot in 2003-'04. This new documentary is as quiet and somber as previous one was gross-out and raucous. It feels like a prayer or a mantra, uttered secretively in a hell where an estimated 1 million people were brutally wiped out in the space of 12 months, and where perpetrators today live in powerful prosperity.

Oppenheimer recently returned to Tokyo to promote "The Look of Silence" after visiting the city last year for "The Act of Killing." He says one thing that has changed this year are the questions the local press is asking.