At first it seems like miscasting. Brendan Gleeson and Emma Thompson are two of the most charismatic, playful, purely present actors working today, scarcely able to do a scene without some sort of spark.

So why would they be cast to play a plain, quiet, grieving, beaten-down German couple in World War II Berlin in “Alone in Berlin”?

It’s the absence of that spark we’re expecting that ends up being key to the performances, and to “Alone in Berlin,” out on DVD and Blu-ray from IFC Films. It makes us understand how much this couple has lost under the Nazi regime, and what it takes for them to foment a tiny rebellion from their dingy flat.

The film is based on the true story of Otto and Anna Quangel. The year is 1940, and like a lot of Germans, they are simply hunkered down and trying to survive the war and the regime. When their teenage son is sent to war and killed, they are nearly broken.

But Otto begins writing postcards. The tiny postcards have anti-Hitler messages written on them, and he drops them surreptitiously all over Berlin. Why? Nearly every German who finds the postcards turns them in to the authorities. But not everyone. In the sweep of history, Otto’s postcards are little more than tiny pebbles in the road for Hitler’s war machine to grind over. But they are there, and the act of rebellion is itself worth something.

Director Vincent Perez doesn’t get us much suspense out of the Quangel’s campaign as he should, aside from a couple of late scenes where the couple are nearly caught. And the film looks excessively beautiful for such a dark subject, capturing Berlin in a golden light that seems at odds with the grim story.

But the lead performances are compelling, and “Alone in Berlin” gathers momentum in the second half with the addition of Inspector Escherich (Daniel Bruhl), a dogged police detective determined to track the Quangels down by traditional investigative methods.

One would assume that Escherich would become the Javert of the movie, but Escherich is more complicated than at first appears. A strict law-and-order man, he’s brutally bullied by the SS into abandoning his by-the-book investigation and using extra-legal means, including torture and murder, to end the case.

In a sense, Escherich and the Quangels start out much the same, as ordinary Germans who simply want to go on with their lives. But the Nazis make that impossible. Some Germans are nudged towards the darkness out of fear, like Escherich, and their souls are destroyed. And, a few, like the Quangels, take small but certain steps of heroism.