A huge hit in France, “Polisse” marks the maturation of writer-director Maiwenn Le Besco (known as just Maiwenn professionally). Having developed her own raw and immediate style over two previous features, the director puts it all together here, in a fascinating multicharacter drama about the police who work in Paris’ child protection unit.

These are cops who see the ugliest, weirdest side of society. A daily inundation of kidnappers, child molesters and abusive and incestuous parents and grandparents is bound to take its toll, and that’s really Maiwenn’s concern here. The individual cases are of interest - they couldn’t not be of interest, given the extreme and fraught nature of these issues. But the film’s focus is mainly on the dynamics of the unit and on the impact the job has on the people who do it.

At center stage are Karin Viard and Marina Fois, who play police partners Nadine and Iris. Nadine is going through the inevitable divorce, and Iris, who has a lot of personal authority, is coaching her to be tough and unbending in dealing with her husband. But beneath her facade of certainty, Iris is unraveling, too, and she has become anorexic.

“Polisse” is a well-observed study of human behavior in extreme conditions. The police attempt to block their emotions, but they can’t, even when they think they can. They present a surface of imperviousness and long-suffering functionality to the criminals, but then make a mess of their own lives, or flare up and scream at each other. They are normal people doing a job, but they can’t catch their breath long enough to return to normality. They’re suffering from battle fatigue, and the battle never ends.

Maiwenn, who appears in the film as a shy photographer documenting the unit, uses multiple cameras. She likes handheld footage. She likes to show people listening as well as talking, and she likes to have actors improvise, based on a script. The style is documentary-like, in that it feels like life and that anything might happen. There is also a nice sense of being in the midst of the action and right there in the room with the characters.