For this movie, I found myself going to the thesaurus, looking up synonyms for "bleak" (dismal, dreary, gloomy, cheerless, desolate) and "agony" (distress, suffering, misery, …) All apply here.
A mysterious apocolypse has rendered the world barren. All plant and animal life has been (apparently) wiped out, except for scattered people. And most of them have reverted to savagery and cannibalism. Set against this are a man and his son, travelling for some reason to a goal variously described as "south" and "to the coast".
They have a few perilous encounters with fellow humans, most of which work out badly for all concerned. Mostly, though, they wander through an impressively dreadful landscape, scavenging for existence. As in most of these flicks, life is solitary, poor, nasty, brutish, and short.
Not my cup of tea, although it got decent reviews. Netflix (incorrectly) thought I'd like it. Although I stayed awake for the whole thing, and I'll tack on an extra half star for a brief, but riveting, appearance by a hard-to-recognize Robert Duvall.