★★
(M) General release (126 minutes)​

The true story behind The Zookeeper's Wife could have been dreamed up by a Hollywood screenwriter – how Jan and Antonina Zabinski,  keepers of the Warsaw Zoo, gave hundreds of their Jewish fellow citizens a refuge during the Second World War.

It's a remarkable yarn, even as relayed in the irritating pseudo-poetic prose of the American writer Diane Ackerman​, whose 2007 book has been brought to  screen by New Zealand director Niki Caro (Whale Rider).

But there is something fundamentally unsatisfactory about this film. What makes the source material compelling also makes it tricky to handle: the mix of real-life horror with elements that, rightly or wrongly, seem almost too fanciful to be true.

Rather than trying to minimise the incongruity, Caro starts out by setting a deliberate fairytale mood.

Jan and Antonina, played by Johan Heldenbergh​ and Jessica Chastain​, are portrayed as rulers of their own little kingdom – living in a villa on the zoo's grounds, and speaking English in what are presumably meant to be Polish accents.

While it doesn't take long for their paradise to come under threat, the sense of unreality persists.

Occupied Warsaw looks strangely clean and prosperous, with only glimpses of the Jewish ghetto. Chastain is used as an uninteresting symbol of virtue, striking the noble poses which are her speciality.

At least her co-star Daniel Bruhl​ has a character to play. As the Nazi zoologist Lutz Heck, he's a creature of pure boyish vanity, who spouts unlikely theories about "breeding" and uses his position of power to sexually harass Antonina while persuading himself she truly cares for him.

The film has some powerful scenes, particularly those that show the killing or mistreatment of animals.

Even here, however, questions persist about the tone and approach. After all, the Nazis justified their worst acts by maintaining that their victims were less than human – and so animal suffering may not be the most appropriate metaphor for Nazi evil in general.

At times during The Zookeeper's Wife, I thought back to Agnieszka Holland's much more effective 2011 film In Darkness, which told a parallel true story about an "ordinary" Pole who becomes a protector of persecuted Jews.

Holland's hero worked in the sewers rather than at the zoo, giving her fewer opportunities for whimsy. But in dealing with this kind of subject matter, perhaps it's preferable to do without cutesy animal reaction shots.