Jim and Elly Mae travel to a distantplanet as guests of Tiro and Mer-members of a super-intelligent race of Ka'ats. On this strange world, work is done by machines, which are controlled by thoughts from the Ka'ats. But Jim and Elly cannot learn this power and become dependent on their hosts for everything- even meals! Determined to find their own food, Jim and Elly explore a nearby city where human-like beings once lived. But fierce robots now march down the streets. Tiro and Mer rush in to protect thier human friends and are kidnapped by the robots. Jim and Elly must use all thier courage and wits to find a way to rescue the Ka'ats.