This film has a very effective aesthetic approach. The camera stays almost completely on hero Saul Ausländer (Géza Röhrig), his heavy lidded eyes and baleful stare at what's happening around him skittish, like an angry and scared caged animal, our view of him claustrophobic because of the aspect ratio.

When we meet him he's helping a room full of people out of their clothes in what looks like an industrial boiler room or cell block, while a voice over the PA tells everyone they're going to be given showers, fed and will get jobs that suit their skills.

If you had no idea what the movie was about without seeing it you'd have little more than a sense of disquiet. It's not until Saul and a few of his fellow workers close and lock the heavy iron doors leading into the shower area that it becomes obvious, trying to stare, impassive, at the floor while increasingly panicked screams and frenzied knocking emerge from the shower area.

As he and his co-workers go back around the room getting all the clothes from the hooks and going through them for valuables, your worst fears (again, if you knew nothing about it) are realised. He's a member of the Sonderkommando, Hugarian Jews selected from amongst people coming in to the death camps to actually work the machinery of mass murder.

His job is to take part in hoodwinking his countrymen into thinking they're being treated as dignified political prisoners while locking them in the gas chambers, pilfering their valuables for collection in boxes even while they scream and die next door. When it's over he and his colleagues drag the bodies out one by one for them to be shovelled into the ovens, something we see him do later just as dispassionately.

And the entire time the camera stays on Saul's face, the weight of the world on his shoulders, the soundscape of screaming or the sight of piles of nude bodies out of focus just behind him, the banality of horror made flesh, Saul behaving as if he's a carpenter building a house, lifting and sawing lengths of wood instead of killing and disposing of dozens of people.

Suddenly, when swabbing blood from the floor (you can barely bring yourself to imagine where it's come from – does Zykon B make victims bleed, or has the panic caused a hysterical rage where they've torn each other limb from limb?), Saul stops, staring in horror at one of the victims, a young boy. It's not just that the poor kid is breathing heavily and hasn't died from the gas – over the next half an hour it slowly emerges that Saul beliees it's his illegitimate son.

He duly reports it to the officers in charge, who drag the boy out and inspect him, all while Saul tries to work and keep a horrified eye on proceedings, watching as the senior officer calmly suffocates the boy to death right there on the table. He orders the body sent to the doctor (also a Jewish prisoner), who Saul visits, pleading with him to hide the body until he can find a Rabbi to give him his last rites.

So begins a dark odyssey amid the Nazi's industrial-scale killing infrastructure as Saul depserately tries to find a real Rabbi – not a fake who just wants a chance to be spared – to help him bury his son. He does so making his way throughout horrors such as the ovens or the pits out in the nearby forest, where columns of people line up to be shot and dumped into mass graves when the gas chambers are overworked.

Saul scurries to and fro from one work area or the terrified chaos and gunfire of the killing fields to another, trying to secure his son's body and find someone to help him say goodbye to it properly. And the whole time, he's peripherally involved in a plot by several of the inmates to rise up and fight back, although Saul is far less interested in intrigue and escape than giving his son a proper funeral.

It's all in Hungarian and even with the benefit of subtitles I found the entire midsection a bit hard to follow. The escape plan involves Saul smuggling a quantity of gunpowder out of the women's camp in the complex, all while trying to keep his head down and out of the view of the nervous, angry uprising organisers only to ready to sell him out if they decide he's not completely on board.

But when the breakout starts and the mood turns from morbid to tense horror, writer/director László Nemes doesn't forget his mission – to keep the camera fixed on Saul's face as he reacts to the mind-numbing horror around him rather than showing us any more than mere glimpses of it.

As a species we often marvel at our capacity for numbness when the numbers associated with death or disaster get too big, and effective/good storytellers know that putting a human face on something so unimaginable is the best way to have it make sense to an audience.

Son of Saul isn't about the Holocaust, the gas chambers, the banality of evil or the plight of wartime European Jews – we don't even look at any of that stuff clearly – it's about a man under distressed circumstances trying to put a loved one to rest – but the approach makes it one of the most effective Holocaust stories you'll ever see.