Just before the kid was born, the world burned. We don't know why, and the characters don't talk about it -- perhaps they don't quite know themselves, or maybe they've decided that it no longer matters. The Boy's universe is grey, full of ash, dust, and the ruins of a civilization he never saw. This is all he knows. His mother, seeing no point in going on, killed herself shortly after his birth. She was not alone. Many of those who didn't take their own lives were soon murdered by the desperate and hungry.
Skip ahead nine or ten years. The kid and his father wander the barren roadways heading south toward the coast for no clear reason other than that it gives them a tangible goal toward which to strive. (And there's always the hope that the ocean will be something other than gray.) Every day is a knock-down, drag-out fight for survival. They run, hide, starve, and fight off attackers who want their food, or their clothes, or, at one point, their flesh.
I set the stage like this not to horrify you or to gross you out, but to give you a sense of the relentless, pervasive grimness of The Road -- and then to turn around and say that The Road may be the most profoundly optimistic and life-affirming film you will see this year. Those who have read Cormac McCarthy's novel of the same name won't be surprised by this. John Hillcoat's faithful, near-perfect adaptation beautifully captures McCarthy's synthesis of all-encompassing darkness and enduring hope.