John Hillcoat's adaptation of Cormac McCarthy's shattering post-apocalyptic fable finally reaches the big screen after a delay of nearly a year. The film, which had its premiere at the Venice Film Festival yesterday, was preceded by the kind of ominous rumbles that build around any movie with a protracted post-production period.

Fortunately, the rumourmongers were wrong -- Hillcoat's vision is forthright and brutal. There are, however, a couple of suspect decisions that suggest a loss of bottle somewhere along the line and that diminish the final film.

A cadaverous Viggo Mortensen plays the father whose only reason to go on living is to protect his son (Kodi Smit-McPhee) day by stolen day. An unexplained cataclysm has obliterated life on Earth. The father and son trek across scorched earth under an ash-smudged sky that forever seems to be closing in, smothering the last flickers of life on the blighted planet.

Post-apocalyptic cinema -- from Mad Max to Twelve Monkeys to Children of Men -- has proved time and again that there is nothing that production designers relish more than a hellish dystopian future to fire their enthusiasm. But even by the striking standards of the genre, Chris Kennedy's work as production designer is remarkable. Kennedy (who previously collaborated with Hillcoat on The Proposition) appears to have harvested all the ravaged, gnarled scrap metal in the Midwest and deposited it in twisted piles of automotive agony in every shot. The film is almost entirely composed of shades of suicidal grey. The monochrome is punctuated by flashbacks to a life before that are infused with the kind of saturated colours that now exist only in dreams.

Like Fernando Meirelles's Blindness, the film suggests that human civilisation is a precariously fragile veneer. Bands of cannibals roam the country; everyone is a potential threat. For those so clearly forsaken by God, He becomes a preoccupation. The man and his son reassure themselves that they are the "good guys", although the child's self-sacrificing generosity is somewhat removed from his father's pragmatic approach to morality in extremis.

Two elements let the film down. First is a voiceover from Mortensen, which is a little heavy on the explication for my tastes. Second, and more serious, is the laboured score (co-written by Nick Cave and Warren Ellis). We know that it's sad that the last children on Earth are starving and scared. We don't need a musical signpost to tell us so.

It would have been better to have no music at all, and let the story play out to the accompaniment of the groans of the dying planet.

Rating: ****