Munich, 1918. Jewish art dealer Max Rothman has returned home after losing an arm in World War One, and meets and befriends a struggling artist called Adolf Hitler.

Not the Adolf Hitler, surely? Well, yes.

Max (John Cusack), himself a frustrated artist (on account of the arm), plays mentor to the same Hitler who would construct the death camps and orchestrate the holocaust.

Now though, in the depressing post-WWI winter, Hitler (Noah Taylor) is still a soldier, holed up in spartan barracks without time or money for painting – though he desperately wants the dealer to exhibit his work.

But while he and Max stroll through parks and discuss Modern Art, his commanders are conniving to include him in their anti-Semitic, anti-communist activities.

Realising his oratory talent, they persuade him to speak at – and spy on – political meetings during the great foment which followed Germany’s humiliation at Versailles.

From an initial reluctance toward politics, Hitler begins to compose not only speeches, but designs the insignia, architectural style and transport network he envisages for a revitalised German state.

The vastness and completeness of Hitler’s vision impresses Max to the extent that, brushing aside his dislike for the artist’s burgeoning anti-Semitism, he agrees to an exhibition of the work.

Most of this, of course, never really happened.

In real life, Hitler did return from the Great War to Munich, and joined a small, new, workers’ party movement, which he went on to lead under the banner of the National Socialist, or Nazi, party.

Max, however, is an entirely fictional character: a construct, as the film’s writer and first-time director Menno Meyjes says, "representative of the profoundly idealistic European Jewish life that reached its apogee before the holocaust".

Cusack, who gets top billing, deals admirably with playing the lead in a film where Adolf Hitler is second fiddle. (Rather like shooting a film about a Hollywood star’s personal assistant where the star appears in every scene, and as the true object of interest, proves too great a distraction for the audience.)

Max is a believable inhabitant of his time: dismayed at the German defeat; dismayed by the war, but financially comfortable, and, despite his smug-smug one-liners ("There is no future in the future") optimistic about where art and good sense can take the world.

Noah Taylor turns in a fairly well-rounded young Hitler. Mostly cold and repressed, he grovels to Max in hope of an exhibition. His frequent sneers and snivelling, and occasional outbursts of shouting or screaming, mirror what we may expect of the dictator-in-training.

Trying to explain the making of the murderer, though, is where this picture lets itself down.

Meyjes quotes Hitler’s architect, Albert Speer (originally quoted by biographer Ron Rosenbaum): "If you want to understand Hitler, you have to understand he was an artist first." An artist first, perhaps. But not only an artist. The attempt made here is to draw a straight line between Hitler’s failure in the arts and his drive for success in his chosen field: aggressive, nationalistic, anti-Semitic politics.

This is a long way to jump, and requires the invention of Max – the historical construct – even to begin persuading the audience of its authenticity.

After one of his more animated speeches, given in a pub, the young Hitler screams in Max’s face: "This is the new art! Politics is the new art!" It rather over eggs the pudding.

For my money the attempt fails. But this doesn’t mean you shouldn’t go and see the film. It is bold to put Hitler in a café with Max and two Jewish girls – one of whom he should be seducing.

Occasional lines startle you into realising he was human, actually: "Hitler, come on – I’ll buy you a glass of lemonade," Max says after his first public speech goes down badly.

Scripting Hitler – at whatever stage in his life – must be daunting for any writer. The temptation must be to heap dark suggestion into his lines. Though largely avoided here, there are some slips: "I see myself teaching," says Hitler, when asked what he sees in the future.

Or in the barracks, early in the film: "The Semitic question is far too important to be left to the individual. It ought to be in the domain of Government – like public health, or sewage."

Other moments make you wonder whether, though the details here are fictional, there must have been many points, on the road to becoming the German Fuhrer, at which Hitler was given the chance to turn aside and do something less destructive instead.

You won’t leave the cinema in an astonished daze after Max, but it will give you pause for thought.

Menno Meyjes had some nerve to make his directorial debut with this film. Though not great of itself, it promises great things for the future.