He is accompanied by Lura, a great cat who is herself a mutant. Together they brave the dangers of an unknown world, with only their wits to guide them. There are other clans and scattered bands of survivors, not all of them friendly, and there is also the threat of the Beast Things- dangerous mutants that prowl the old cities. Together Fors and Lura find the lost city, the remnants of an ancient civilization, and uncover a shocking truth that may doom the clans forever.
This was one of the earliest books I read by Andre Norton, and remains one of my favorites. It's a thrilling adventure story, and presents a world that is both dangerous and exciting at the same time. I was anxious to see what Fors would discover in the great ruined cities, and also if he would be able to return to his clan and assume a place of honor among them. There are lots of nice moments in this one. At one point Fors hears drums in the night and wonders who else is out there. At another point Fors is ambushed and leads a harrowing chase over rooftops and through the streets of a deserted city. Great stuff.
This book was also released under the title Daybreak 2250AD, with a different cover. That title gives the sense of a new beginning, I think. This is a great introduction to Andre Norton if you've never read her work, and a superb vintage science fiction novel.