“The Unknown Girl,” the latest film by the Belgian writer-directors Jean-Pierre and Luc Dardenne, is about the consequences of trying to do the right thing. By a logic at once elusive and meticulous, it is also, therefore, about the consequences of inaction. Moral indifference is an easy path, and it leads to other, graver sins, including cruelty and dishonesty. But the harder road of decency has its own traps and byways, as a young doctor named Jenny Davin discovers.
Jenny, played with somber concentration by Adèle Haenel, is devoted to her profession and her patients. She is thorough and compassionate, scolding her intern (Olivier Bonnaud) for failing to keep his emotions in check and communicating clearly and efficiently with the mostly poor people who come to her office. On the verge of moving into a more prestigious position, she decides, almost impulsively, to stay where she is, and take over her retired mentor’s small general practice. It’s what she loves, and she is loved in return.
But in the Dardennes’ moral universe the ways of love are never simple. Having established that Jenny is a good person, the film allows her what at first seems to be a trivial lapse. Late one evening, long after office hours have finished, the front buzzer sounds and Jenny decides to ignore it. (That buzzer and the functional ringtone on Jenny’s cellphone are the film’s principal sound effects and the closest thing it has to a musical score.) The next morning, a woman is found dead nearby, and security video identifies her as the person who had been at Jenny’s door.
Not much else is known about her, and Jenny, in a fit of self-reproach, tries to compensate for her neglect by finding out what she can. As…