The Pnume are native to Tschai, living underground in a vast network of caverns with their human slave-species, the Pnumekin. Historians of Tschai, the Pnume collect its past with scholarly disinterest; they hear rumors of Adam Reith - a man who claims to come from another planet, named Earth - and they want him for permanent display in Foreverness, museum of Tschai life! Reith must survive the Pnume tunnels, if he is ever to return to Earth.