An unnamed father and his young son journey across a grim post-apocalyptic landscape, some years after an unspecified apocalypse has destroyed civilization and most life on Earth. The land is filled with ash and devoid of living animals and vegetation. Many of the remaining human survivors have resorted to cannibalism, scavenging the detritus of city and country alike for flesh. The boy's mother, pregnant with him at the time of the disaster, gave up hope and committed suicide some time before the story began, despite the father's pleas.
Realizing they cannot survive the oncoming winter where they are, the father takes the boy south, along empty roads towards the sea, carrying their meager possessions in their knapsacks and in a supermarket cart. The man coughs blood from time to time and eventually realizes he is dying, yet still struggles to protect his son from the constant threats of attack, exposure, and starvation.