America is a grim, gray shadow of itself after a catastrophe. A man (Viggo Mortensen) and his young son (Kodi Smit-McPhee) wander through this post-apocalyptic world, trying to keep the dream of civilization alive. They journey toward the sea, surviving as best they can on what they can scavenge, and try to avoid roving gangs of savage humans who will turn them into slaves, or worse.