From the back cover blurb:

Call it soul, call it humanity, species - sentience, anything - it was missing. And not only was it gone from mankind, but from man's ancient enemies, the rats, as well. There was no will to power, no will to live... Both intelligent species were dying.

The task of regenerating the world fell to Kavan Lochlain, the last living coward. The only man who cared enough to feel fear, Kavan was afraid of everything. But this fear was going to take him to the Cradle of the Sun, because he was too frightened to let anything stop him.