Adolescent Sturm und Drang is given a particular historical frame and significance in Sally Potter’s Ginger and Rosa, as the emotional questing and turmoil of two 15-year-old English girls is experienced in the shadow of the Cuban Missile Crisis. Ginger (Elle Fanning)and Rosa (Alice Englert) are lifelong friends whose mothers met in a maternity ward in the late 1940s. Even before we see the short montage of scene snippets from this prologue, Potter starts things off with a shot of an atomic mushroom cloud and brief shots of a destroyed Hiroshima in August of 1945, bluntly reminding us of the peril of Cold War politics. Radios broadcast tense reports of the gathering crisis of the United States’s challenge to the Soviet Union’s emplacement of anti-missile batteries in Cuba. A BBC news reader is heard reporting an expert estimate of over 270 million worldwide deaths if a nuclear exchange ensues.

Against this looming international exigency, the two girls lead an adventurous, exploratory existence, roaming London at night, hitching rides across the countryside, staying out until 2am, despite the weak protests of their mothers. Ginger’s father Roland (Alessandro Nivola) is even less interested in supervisory responsibility. This pacifist writer and teacher is disdainfully dismissive of middle-class domestic conventions.

Ginger says the two “should really do something about the bomb” and they attend a small anti-nuclear meeting (where an earnest young discussion leader misattributes Lenin’s “What Is To Be Done?” to Engels). But Ginger’s increasingly serious, even impassioned concern about war and the bomb isn’t shared by her friend. The sexually precocious and romantic Rosa is drawn, all too willingly, into an affair with Roland, and with disastrous consequences.

Potter deftly establishes the setting, a London on the brink of the Swinging Sixties, still feeling the effects of post-war austerity, and a socially marginalized leftist milieux. The early scenes of the girls’ urban adventures and shared philosophies and confidences are sympathetically handled. But Potter, who also wrote the film, never really establishes persuasive control of the movie’s direction. The adults hovering around the two youngsters are emotionally thwarted and ineffectual, dubious exemplars and advice providers, their political commitments notwithstanding. Roland would seem to be recklessly self-serving, but Potter treats him gently, almost poignantly. Rosa’s mother Natalie (Christina Hendricks) might be an interesting, conflicted figure, but the movie neglects her too much.

Fanning’s work is consistently, sometimes strikingly good, and the entire cast – including Oliver Platt and Timothy Spall as a gay couple and an ill-used Annette Bening – is admirable, but the movie doesn’t cohere. Potter’s focus is too unclear. We can’t know if she’s more interested in a coming-of-age during one political and historical moment, or the melodrama of relations among these troubled people.

Watch the trailer for Ginger & Rosa