Making films critical of the Iraq war is a risky business. When this sober, intelligent drama was released in the US last year, Right-wing critics dubbed it "Bin Laden cinema". Spooked audiences stayed away in droves. Let's hope we Brits are more curious.

Oscar-winner Paul Haggis's follow-up to Crash offers what is in many ways a predictable "journey" for its retired army hero Hank (Tommy Lee Jones) - but where it winds up is genuinely shocking.

It would spoil the movie to give too much away about the ending. Suffice to say that Jones - who seems to be everyone's favourite leading man at the moment - is in fine form as Hank Deerfield, a dad trying to find out how his soldier son, Mike, got killed days after returning from Iraq.

The 62-year-old actor does his intense-garden-gnome routine to perfection; when Hank arrives in Fort Rudd, New Mexico, he arouses our curiosity simply by widening his exhausted eyes.

Later, he hurriedly dons a shirt when a woman approaches him in the laundrette. It's easy to believe in this man's old-school machismo - just as it's easy to believe he's impossibly shy.

Charlize Theron - as the single-mom cop who decides to help him in his search - has a harder job. Neither the serious brown hair-do, nor drab uniform can disguise the shallowness of detective Emily Sanders.

This character belongs in TV-land and never escapes. Susan Sarandon, playing Jones's distraught wife, is similarly hemmed in. We're supposed to be undone by her grief. But the script prods so hard I felt more inclined to giggle.

Luckily, the unknown actors playing Mike's military buddies are less easy to peg. In fact, it's they who alert us to Haggis's more sophisticated agenda.

Their polite smiles and ever-so-slight impatience with the old-timer create an unnerving atmosphere that makes your heart race.

The film's title, by the way, is a reference to the Bible story about David and Goliath. As Jones explains to Emily's dorky kid, that famous fight took place in the Valley of Elah. David wasn't frightened of taking on the giant - his bravery, not his weaponry, was what gave him the edge.

The kid can't quite believe this and the mysteries of the story continue to echo as Hank and Emily's own fight nears its close. Is it possible to be both strong and virtuous? Is it possible to be brave and still lose?

In The Valley of Elah's churning last half-hour makes up for any crudeness that's gone before. I could have done without the wise Latino. Or the Annie Lennox track that accompanies the credits (Annie apparently let Haggis have this lachrymose dirge for free - trust me, it's a gift he could have done without).

But nothing can break the spell created by Haggis's hard-working team - especially those young soldiers. It has been implied that the director's nationality - he's Canadian - is responsible for the movie's "unpatriotic" stance. To which one can only say: God bless Canada.