An insubordinate space captain investigates an apparently deserted but unstable planet after being drawn there by a mysterious gravitational force. He and his expedition discover the remnants of the once dominant civilization living on a subsistence level in caves. Long ago their advanced society had become so complacent that they built a super-computer to run and maintain the machines that supported their indolent, self-indulgent lifestyle. After the machines were destroyed by a meteor shower, the inhabitants found themselves without the knowledge to rebuild them, completely subservient to the computer whose megalomania was now unchallenged. The cruel cyber-despot reveals that it arranged for ship's landing because it needs the skills of the Earthlings to make critical repairs in its damaged circuitry. When the computer announces future plans for the conquest of the Universe, the captain and his crew know it is time to act.