Film of the week: Changeling (15)

I don't, personally, swallow the notion that Angelina Jolie is the world's most beautiful woman; but she's certainly the world's most something woman: her face isn't entirely earthly, its proportions suggestive of different gravities or different evolutionary imperatives – a science-fiction face. Even in a contemporary film, she looks out of period; in a period film such as Changeling, set in the Los Angeles of the Twenties and Thirties, her presence is bizarre. Not that bizarre is entirely a bad thing, with a director who is getting a little too inclined to give in to solemnity and civic decency.

Changeling is based on the real-life case of Christine Collins, a single mother whose son Walter disappeared from her house in March 1928, while she was at work. Five months later, their lacklustre performance having raised some dust in the press, the Los Angeles police proudly announce that Walter has been found halfway across the country, in Illinois, and a grand public reunion is arranged: except that the boy isn't Walter at all. Under pressure from the police, Christine agrees to take him home – perhaps she's in shock, perhaps his ordeal changed him – only to discover that somewhere along the way "Walter" has lost three inches in height and his foreskin. The notoriously corrupt and incompetent LAPD is at first patronising ("His identity has been confirmed by the best minds in the field of child identification"), then hostile, suggesting that she is trying to dodge her responsibilities as a mother. When she persists in saying he's the wrong boy, they throw her into the local mental hospital on grounds of paranoid delusions. She's saved by the intervention of a local pastor (John Malkovich, playing things unusually straight) with a crusading radio show, and by the revelation that a psychopath has been roaming Los Angeles, kidnapping, imprisoning and murdering young boys – and Walter was almost certainly one of his victims.

Changeling sits comfortably in a Hollywood tradition of placing itself at the centre of a world of squalor and corruption: in the sepia-tinged colour schemes and the bullying men in hardwearing fabrics, it's easy to catch echoes of films about LA's wicked past, like Chinatown or The Black Dahlia. Odd lines remind you that Christine's suburban world nudges up against the surreal enchantments of Hollywood – the changeling child's admission that he went along with the pretence because he thought he might meet Tom Mix and get a ride on his horse. There are other resonances: the contrast Eastwood paints between the raindrenched LA streets and the parched desert where the monster dwells seems to have been borrowed from David Fincher's Seven; while Christine's stay in hospital (the casual use of electric shocks to punish, the insistence that she can be certified sane if she'll just admit she's mad) feels like a hybrid of One Flew Over the Cuckoo's Nest and Catch-22.

So one flaw in the film is a sense that the story is too neatly packaged, squashed into a series of ready-made scenes and characters (bad cop, decent cop, plucky prostitute with heart of gold, giggling psychopath). At the same time, there's too much story here to be plausibly contained within one film. It's partly the surreal, horrible scale of the murders, alongside which Christine's grief seems like a sub-plot; partly that Eastwood and his screenwriter, J Michael Straczynski, don't know how to end things. Changeling clips along nicely for the best part of two hours – I don't go along with the critics who have said it's too slow – but every time it seems to reach a natural conclusion, along comes something else: now Christine has to attend the killer's trial; now she has to visit him in jail; now she has to watch him get hanged; now there's a hint that Walter may not have died (one peculiarity is that the moral eschews the modern preference for "closure" in favour of the more old-fashioned goal of hope).

Some of the dialogue is clunky, the action implausible – the pastor arrives at the asylum to save Jolie at the very second she's about to have a gazillion volts zapped through her cranium; visiting her son's putative killer in jail, Jolie rams him up against the wall and slaps him about as she screams for the truth. That moment puts her physique and genuine scariness to good use, but you're never caught up in it enough to think it's even faintly plausible that a young woman and a convicted killer would be left so free and alone. An inclination towards melodrama is emphasised by Eastwood's own rather syrupy music, which every minute seems determined to impress on us that the murder of small children and the imprisonment of innocent women are serious matters.

But I liked the film: I liked its attention to detail, I liked a lot of the acting (especially Jeffrey Donovan as the police captain who won't let Christine upset his applecart), I liked the streak of almost Kafkaesque humour (the police paediatrician who tries to persuade Christine that trauma might have shrunk her son's spine). There are so many hints of a really good film lurking here that at times it feels as if the real article has been stolen away, an inferior knock-off put in its place. Heck, I'll settle for the one I've got.