"Cannibalism is the biggest fear," warns "The Man" (Mortensen) as he surveys a post-apocalyptic landscape of withered trees, drifts of ash and derelict buildings.
Muffled in grease-stained puffa jacket and pushing his grimy possessions in a dented shopping trolley, he's accompanied by his gaunt son "The Boy" (Smit-McPhee) as they toil across the barren tundra.
Through a series of flashbacks, we see how The Man's marriage to The Woman (Theron) fractured following the birth of their son and an unexplained nuclear winter returned civilisation to the stone age.
Now, years on, they have to desperately forage for food (mainly canned so it hasn't rotted), stay warm in a perpetual dusk and hold their resolve as they trudge along abandoned freeways towards the coast.
However, the lethal threat comes from gangs of feral marauders roaming the dust-coated hills and valleys, hunting down stragglers like The Man and The Boy like carrion to be killed and consumed.
After writer Cormac McCarthy's novel No Country For Old Men was so masterfully adapted for the big screen by the Coen Brothers, director John Hillcoat performs a similar service for The Road.
Make no mistake, this is a grim watch: human larders fester in the cellars of creaking mansions and flesh-eating ghouls scour fields of ash for the innocent all against a backdrop of Stygian gloom.
Yet there is hope. The intrinsic goodness of Mortensen's protective dad and his son's innate morality survive the oppressive desperation that has driven basic humanity from others.
Their bond is unbreakable and its steely strength propels them forward - faltering occasionally: The Man has to be won round to show charity to Robert Duvall's hobo - more in grim hope than sunny expectation.
There are a couple of gripes. The score - civilised strings and piano - doesn't sit well with the ecological hades in which they find themselves and the ending seems brighter than the book.
But, no matter. This is a superlative piece of flim-making. Terse, raw and unadorned, there are no cheap tricks to devalue a story of unconditional love,