In wartime Berlin, Anna Quangel (Emma Thompson) belongs to the Nazi Women's League, whose members are charged with visiting the wives of German soldiers to ensure they're doing the best for the war effort. Slackers are given a forceful lecture – unless their husbands are particularly high in the pecking order. In that case, righteousness is well-tempered with diplomacy.

Thompson as a Nazi? That quintessential Englishness and stalwart sense of decency make the idea just about impossible to swallow. But you don't have to chew on it for long. When her son is killed at the front, Anna bows out of the League in spectacular fashion. While calling on the particularly intransigent wife of a leading stormtrooper, she abandons all caution and lets her have it.

It's a scene which lifts Alone in Berlin out of the familiar rut carved out by film and television series about the evils of Nazism. Anna and her husband, Otto (Brendan Gleeson), are a working-class couple who have never voiced their doubts about Hitlerism. But with their son's death, everything changes and Otto embarks on a simple plan. He will write postcards criticising the Reich and leave them in buildings all over Berlin.

This small act of rebellion, which he likens to throwing sand in the gears of the Nazi war machine, is almost certainly suicidal. He and Anna know it. Yet they persist, and with his account of their persistence, writer-director Vincent Perez gives us a snapshot of Berlin life in 1941.

It's a true story, drawn from a 1947 novel, Every Man Dies Alone by Hans Fallada, who was inspired by the heroism of Berliners Otto and Elise Hampel, and it's already been dramatised by German TV. Perez and his producers originally wanted to make the film in German, too, but it wasn't until the book's English translation turned it into a bestseller that they were able to get financing.

At that stage, Thompson signed up, followed by Gleeson, who obliterates his Irishness with a spot-on German accent matched with a stolidly convincing air of purpose.

The apartment building where the Quangels live is laid out in a declining moral pattern. Sharing the top floor with them is a retired judge whose reputation for professional cold-bloodedness is offset by personal courage and an unassailable passion for justice. It's these three who come to the aid of the elderly Jewish woman who lives on the floor below. Without them, she would be at the mercy of the Nazi hooligans in the basement.

Expect no fireworks. Perez directs in stately style with an eye to the subtleties of character and the way the Reich's brutalities filter down into the everyday. It's that juxtaposition – of the hellish against the ordinary – which gives the film its punch.