Mankind has been forced to flee Earth due to pollution and man made diseases. But the same diseases that killed man caused speeded up evolution in dogs, cats, elephants and rats.Now a scouting party of "demons" as men are called by the intelligent animals has been sent back to Earth to see if man can once again live here.
Classic Andre Norton tale---
When desperate measures failed to control what men had begun and could not stop, Man fled his polluted planet, leaving behind an epidemic virus born of experimentation. Yet unlike men, whom the disease could destroy, the animals of the planet thrived, each generation more forceful and intelligent than the last.
In the ruins of what was once a university complex, a vast band of cats, more highly evolved than those on the outside, sought to master the works of man. And they learned that the nearly mythical Demons--as men were called--were not legendary, but real.
Then one day a spaceship landed . . .