Hanna (12A)

Starring: Saoirse Ronan, Cate Blanchett, Eric Bana

The teenage actor Saoirse Ronan looks right at home in the Arctic. With her startling ice-blue eyes, pale skin and fleecy white-blonde hair she's like her own camouflage unit, nearly invisible as she stalks among the snowbound woods of North Finland.

No wonder she can bring down a reindeer with her bow and arrow at 30 paces. Ronan plays Hanna, who's spent her whole life in this frosty wilderness, raised by her widowed father Erik (Eric Bana), an ex-CIA agent who went underground years ago and took his only child with him. Since then he's trained her in the gentle arts of hunting, pistol-shooting and how to snap a man's neck with her bare hands.

Despite having only each other for company, father and daughter get along fine, it seems, in their remote log cabin. He has educated her, rather austerely, from just two books, an old encyclopedia and a collection of fairytales, though she also turns out to be fluent in German, Italian, Spanish and, later, Arabic. "Think on your feet," he tells her, "even when you're asleep." Quite a tall order, that, but if anyone can do it, Hanna can. "I'm ready now," she tells him – for what, we don't yet know – and Erik realises that a teenager, even one who has lived wild with furs and longbows, needs to get out a little.

This intriguing set-up is the work of Joe Wright, a director who has exhibited a lively interest in complex, independent-minded young women. His first film Pride and Prejudice (2005) took on perhaps the most beloved embodiment of the type, while his second, Atonement (2007), went bravely in the opposite direction in terms of sympathy, focusing upon a meddlesome miss whose fantasies bring ruin to her family. This latter was also played by Ronan, who even at 13-years-old gave notice of a scarifying poise to go with that unsettling thousand-yard gaze. Wright is evidently banking on more of the same from his young star in Hanna, the difference being that he's not got Jane Austen (or Ian McEwan) for an ally this time, but a script by Seth Lochhead and David Farr. Could this be why the film, once it emerges from its Arctic fastness, breaks apart so spectacularly?

Once Hanna has been allowed to venture into the big bad world, she instantly becomes the quarry of a hard-as-nails CIA officer, Marissa Wiegler, played by Cate Blanchett in a tailored grey suit and a severe auburn bob. She could almost be auditioning for the role of "Rosa Klebb: the Early Years". Marissa wants the girl and her father eliminated, for reasons that aren't clarified until the film's last reel, though don't torment yourself with intricate psychology – the film-makers certainly haven't. In one of the film's earliest floutings of probability, Hanna is abducted in Finland, imprisoned in an underground concrete bunker, and escapes through a long tunnel into – salam! – Morocco. Even a Bond movie, the most geographically promiscuous in cinema, would throw us the occasional bone of an in-flight scene, or a plane landing. Having footslogged through the desert she has a disorienting night in a hotel room, where her rather lopsided upbringing starts to make life difficult. While Erik may have equipped her to take on Jason Bourne, he hasn't taught her a thing about music, electricity, human interaction. Thanks, dad!

Somehow she attaches herself to a couple of English pseudo-hippies (Olivia Williams and Jason Flemyng) on tour in Morocco, and makes friends with their sensationally annoying daughter (Jessica Barden). And from this point the film keeps conking out, its fuel entirely derived from movie life rather than the real thing. (Lochhead wrote it when he was 24, which may account for its synthetic nature). If Blanchett's Marissa looks only half-baked from celluloid, try making sense of Tom Hollander as the world's shortest and unlikeliest hitman. Hollander's Mr Collins was one of the highlights of Wright's Pride and Prejudice, but here with his peroxide hair and German accent he looks more like a gay-porn impresario. A stop-start chase sequence develops, but it's mysterious why Hanna should be fleeing from him at all – she could beat the shit out of this squirt with one hand tied behind her. If Hanna is the innocent-but-deadly killer we have been led to suppose, then the film must back up that idea. Sadly, consistency is one of its notable victims, particularly in the matter of Hanna's Girl Who Fell to Earth status. We see her freaking out, for instance, when a telephone rings, but later she's perfectly happy downloading stuff from Google.

What baffled me more was why someone as literate as Joe Wright fancied directing this material in the first place. It looks like a script designed to test his patience more than his skill. True, he does one action sequence very well, echoing his bravura (you may argue "show-off") tracking s06052011hot during the Dunkirk arrival in Atonement. Bana, missing from the movie for long stretches, is pursued down into an underground station in Berlin where four G-men ambush him. The style of the fight, the urban location and the sense of conspiracy afoot insistently recall the Bourne movies, though Hanna falls way short of them as entertainment. Does Wright secretly want to be the next Paul Greengrass? Odd, if so, because his best work hitherto suggests a film-maker with a different, more literary voice: his own, in short. Let's hope this vague, derivative thriller is just a blip.