Time is running out to find a settled home for the nine-year-old Bernadette, known to everyone as Benni, whose angelic appearance belies a simmering, foul-mouthed fury which constantly breaks out against allies and enemies alike.

System Crasher (Systemsprenger) is a remarkable achievement. Without overly sensationalising what is a bleak and often repetitive situation — in which, as the title suggests, a child’s recklessly aggressive behaviour keeps ‘crashing’ the care system set up to help her — this film manages to be continuously gripping and intense, delivering a series of emotionally devastating moments as it tells its story. Much of the credit for this must go to its young star, Helena Zengel, whose performance as the simultaneously obnoxious and charismatic Benni has an energy, spontaneity and absence of affectation which must surely have been technically challenging to achieve. One of the most impressive elements of this performance is its externality, as Benni constantly pushes all the hurt and anger she feels out into the world. Her few moments of self-reflection are all the more affecting because of this.

The rest of the cast give appropriately low-key, naturalistic performances, which nonetheless offer sufficient individuality to suggest the various viewpoints and motivations of the professionals who try to help Benni, from foster parents to child psychologists. There are highlights from Albrecht Schuch, whose character Micha is flagged from the start as the maverick who, it seems, will finally get through to Benni, and from Gabriela Maria Schmeide as the fussy, patient Frau Bafané, who in many ways is the most consistent figure in Benni’s life and who, late in the film, delivers one of its most poignant moments. Lisa Hagmeister, in the difficult role of Benni’s overwhelmed mother — the person whose inability to cope with her daughter seems to have wrecked Benni’s relationships with everyone else — pinpoints the essential weakness and irresponsibility of her character without making her wholly unsympathetic.

In line with the general naturalism of the film’s approach, writer-director Nora Fingscheidt mainly sticks to a documentary style of shooting, though she often achieves exhilaratingly kinetic effects in the scenes where Benni dashes through the outside world creating her own brand of mayhem. A few expressionistic sequences try to give a sense of the jumble of thoughts going through Benni’s head, often relating to happier times with her mother and the mysterious trauma from her early childhood that has left her unable to bear anyone except her mother touching her face.

For all its undoubted qualities, there is a curious dichotomy at the heart of this film. On one hand, it tells is the story of a profoundly disturbed little girl, simultaneously craving and rejecting love, and the overstretched care system that goes above and beyond to help her. On the other, there are hints that, despite her destructive inability to control her impulses, Benni is mainly misunderstood and that there is even something positive and liberating in her larky, anarchic behaviour. Of course, it may well be that it is the tension between these two positions which gives the film its compelling dynamism.