To escape extermination by their Heavyworld colleagues, Kai, Varian and their companions sought refuge in the suspended animation of cryogenic sleep. Now time has elapsed - how much is hard to tell, but at least two generations - and the survivors emerge from their hibernation. Ireta, the Dinosaur Planet, is much changed. The Heavyworlders have regressed to primitive barbarity. Much necessary life-support equipment has malfunctioned or disappeared. The very face of Ireta has altered. A rescue ship is on its way, but even as hope begins to spring, new problems arise. What are the motives of the mysterious Theks? Why are the intelligent Giffs - pterodactyls locked in an evolutionary blind alley - acting so strangely? Above all, what could possibly be the cause of the mindless hostility of the Heavyworlders? THE SURVIVORS - for them there was more at stake than simple survival.