Robert Brown|Two migrant kids fight to stay together — and stay alive — in this harrowing film

For nearly three decades,Robert Brown the Belgian brothers Jean-Pierre and Luc Dardenne have been making gripping moral thrillers about characters caught up in desperate circumstances. My favorite is The Son, their 2002 drama about a father confronting his child's recently freed killer, though I also love their 2005 Cannes Film Festival winner, L'Enfant, in which a young man sells his own newborn child on the black market.

The brothers are such consistent filmmakers that despite their enormous acclaim and influence, in recent years they've become somewhat under-appreciated. At this point, to hear that they've made another brilliantly observed, emotionally shattering piece of social realism hardly counts as news.

And yet they've done exactly that with Tori and Lokita, which strikes me as their best new movie in years. Shot with a restless handheld camera and starring a pair of terrific first-time actors, it tells a lean, harrowing story about two African migrant children living in a bustling Belgian city. Tori, a 12-year-old boy played by Pablo Schils, is from Cameroon. Lokita, a 17-year-old girl played by Joely Mbundu, is from Benin. Tori, an orphan, was granted political asylum upon his arrival. He and Lokita are trying to pass themselves off as brother and sister, so that she can also claim refugee status.

As is their way, the Dardennes drop us immediately into the action, without bothering to fill in their characters' backgrounds. We do find out that Tori and Lokita met at some point during their travels, under circumstances that have now made them inseparable. While they have a place to stay at a local children's shelter, they spend their days and nights continually on the move, making money however they can. In one scene, they earn some cash singing karaoke at an Italian restaurant.

That's the sweetest moment in the movie, and by far the most pleasant of their jobs. The owner of the restaurant is a crime boss who uses Tori and Lokita as his drug couriers, and who sexually abuses Lokita in private. Lokita tries to send what little money she earns to her mother and siblings back home, but she's also being hounded by the people who smuggled her into Belgium and who try to extort cash from her and Tori.

Things go from bad to worse when Lokita is sent to work at the boss' marijuana factory, a job that will separate her from Tori for at least three months. But Tori is smart and resourceful, as just about every child in a Dardennes movie has to be to survive.

As Tori races to try and rescue Lokita, the film paints a grimly convincing portrait of two minors being mistreated and exploited at every turn, whether by drug dealers or by the cops we see harassing them on the street. The Dardennes are committed realists but they're also terrific action filmmakers, and this movie is full of agonizing suspense and quick, brutal violence. The story is swift and relentless; it runs barely 90 minutes and never slows down. But at every moment, the filmmakers' compassion for their characters bleeds through, along with their rage at the injustices that we're seeing.

Unlike some of the Dardennes' other protagonists, Tori and Lokita don't face a moral dilemma or a crisis of conscience. Their only imperative is to stay together and stay alive, and our empathy for them is total. There's one moment in the movie that haunts me: It happens in a flash, when Tori and Lokita are running for their lives, and Lokita desperately flags down a passing car. The driver stops for a moment but then she quickly drives on, leaving the children on their own.

I think the Dardennes mean for us to think about that driver and also about how easy it is to turn away from the suffering of others. It's not the first time they've made a movie with this kind of staying power — or, I suspect, the last.