“I will.”

This is the first line spoken by Saul Ausländer (Géza Röhrig), 11-and-a-half minutes into Son of Saul, the Hungarian Holocaust drama of which he’s the protagonist. And these two brief words, when they finally come, are freighted with contradictory meanings.

Saul is a member of the Sonderkommando at Auschwitz, the Jewish prisoners who were tasked with escorting their fellow Jews into the death chambers and disposing of their corpses afterward. Though the status was presented by the Nazis as a privilege—the Sonderkommando could remain alive somewhat longer than their condemned brethren—it was in fact a deeper curse: They, too, would be exterminated in a matter of time, but only after being forced to collude in their own genocide.

In this sense, Saul’s “I will,” is merely the acquiescence of the enslaved, the acceptance of yet another in an endless series of grotesque duties. Yet given their context, the words are also a gesture of quiet defiance. Saul has seen the dead body of a boy he believes to have been his son: In volunteering to take responsibility for the corpse, he is setting in motion a plan—one which will serve as the central thread of the film—to spare the boy from the ovens and give him a proper Jewish burial.

Son of Saul is the debut film of the 38-year-old director László Nemes, and it is a work of remarkable power, a chilling investigation into the intimate mechanics of mass murder. We watch as the Sonderkommando herd unknowing victims into the “showers,” while German officers promise a hot meal on the other side. When the doors close, we watch them immediately begin to collect the belongings of the doomed, even as the latter begin to scream inside. Afterward, we watch them drag out the naked bodies and scrub down the floors for victims yet to come. We watch them shovel coal for the ovens; we watch them shovel human ashes into a river.

Most of all, we watch Saul. The camera hugs him close throughout almost the entire film, peering over his shoulder such that it presents the camp from his perspective while keeping his face (and the large red X on his back that marks him as Sonderkommando) in the frame. Nemes uses shallow focus both to keep the audiences’ eyes on his protagonist and to keep the horrors surrounding him—the arbitrary executions, the ever-present corpses—at a slight remove that’s simultaneously humane and disconcerting. The narrow, box-like frame of the film emphasizes a profound sense of claustrophobia and containment.

The movie is at once clinical in its accumulation of small details and dreamlike in its execution, a waking nightmare through which Saul somnambulates, the audience right alongside him. Röhrig, a poet as well as an actor, is fascinating in his opacity. Though the discovery of the boy has given him a goal, it’s clear that any larger sense of purpose he might have harbored has long since been extinguished. Survival itself seems hardly worth the effort.

Nuggets of genuine horror abound. The German guards refer to Jewish corpses as “pieces” (“Move the pieces!” “Burn the pieces!” “One Jew for one piece!”). The initial reason why the boy whom Saul believes to be his was singled out is that he didn’t quite perish in the gas chamber. In a cruel inversion, a white-jacketed Nazi doctor places a stethoscope on the boy’s chest to listen to his vitals, before covering his mouth and nose to end his breathing. An autopsy is commanded not in order to determine the cause of death but rather to determine the cause of non-death.

Even as Saul pursues his solitary mission, an uprising is being plotted around him. (There was, in fact, a Sonderkommando revolt that took place at Auschwitz in 1944.) It’s here that Nemes perhaps offers more detail than is necessary. The elements of the insurrection and the power dynamics between the various Sondercommandos—the kapos and oberkapos, the competing units—all remain decidedly hazy. Though perhaps that’s precisely the point.

Son of Saul has already won the Grand Prix at Cannes and the Golden Globe for Best Foreign Language Film, and it’s a clear favorite at the Oscars next month. It is not—if my description has somehow failed to make this clear—an easy film to watch. But it is a forceful and unsettling addition to the cinema of the Holocaust, a film that digs deeply into the gruesome workings of the death camps and ponders questions about duties to the living and duties to the dead.