Clint Eastwood's stolid thriller, which had its world premiere at Cannes last night, provides an unnerving parallel with one of the most troubling and provocative stories of the past 12 months. L'Échange — which, before it landed in Cannes, was called Changeling — tells the tale of Christine Collins, a telephone operator who kissed her nine-year-old son Walter goodbye on a March morning in 1928, and didn't see him for the next five months. Her extraordinary battle to find the child chimes all too loudly with tabloid headlines that haunt the nightmares of every parent. The film, based on fact, is a worthy and bleeding tribute to Collins.

I shall eat the next person who tells me that Angelina Jolie cannot act. Starring as Collins, she is the entire, anxious point of Eastwood's film, and absolutely terrific as a mother who is forcibly reunited with the wrong boy by a Los Angeles Police Department rotten to the core. The high and mighty — namely Mayor George E. Cryer and Police Chief James “Two Guns” Davis (played by Colm Feore) — have an almost psychopathic desire to create good news so that their shoddy house-of-cards empire doesn't fall around their ears. This being prewar LA you can't turn a corner without Clint reading you a chapter from Hollywood Babylon.

Thank heavens for the unpronounceable Reverend Gustav Briegleb, aka John Malkovich, the most unreverential saviour this side of Chairman Mao. He is a celluloid drip-feed of hope and strength. Jolie's interminable struggle with the seedy authorities is hedged by tense scenes in which Malkovich throws himself around City Hall like a wrecking ball.

Having done some mayoring himself, Eastwood is in a position to play judge and jury when the film delves into the grisly depths of Gordon Northcott's serial killing farmstead — a great performance by Jason Butler Harner as the convicted child killer. Children in peril is a theme Eastwood visited before, in Mystic River, starring Sean Penn, president of this year's Cannes jury.

The period detail in L'Échange is sumptuous. The anguish of Jolie's performance is inexplicably real. The soundtrack hums, and you can smell the era. The courtroom scenes where Jolie fights for attention are tear-jerkingly awful. But there is a fatal sliver of corniness about Eastwood's bid for the Palme d'Or. His characters tend to announce themselves the moment they arrive on screen. The twists are too easy to guess and the colourful complexity of the nostalgia is too black and white. That said, Eastwood's film touches very real nerves.

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