One

SURVIVING IS ONLY THE BEGINNINGThis is the United Kingdom, but it's no country you know. No place you ever want to see, even in the howling, shuttered madness of your worst dreams. You survived. One man.You walk because you have to. You have no choice. At the end of this molten road, running along the spine of a burned, battered country, your little boy is either alive or dead. You have to know. You have to find an end to it all. One hope.The sky crawls with venomous cloud and burning red rain. The land is a scorched sprawl of rubble and corpses. Rats have risen from the depths to gorge on the carrion. A glittering dust coats everything and it hides a terrible secret. New horrors are taking root. You walk on. One chance.

Synopsis from Open Library.