Answering a distress signal, Commander Koenig is forced to crash-land his Eagle on Entra - moon of the planet Ellna - which turns out to be the planet's penal colony, and Koenig finds himself a prisoner of the beautiful Elizia and her equally beautiful prison guards.

The arrival of the Alphans on another planet seems to cause a change in its atmosphere, setting off pollution and poisoning of the water. They meet Zoran, the sole survivor of the last exploratory force, who tells them that the planet is controlled by an immortal being - with whom Koenig must parley if he and his crew are to leave the planet alive.

The Dorcons -the most powerful race in the galaxy -demand that the Alphans hand Maya over to them. Koenig refuses, until Moonbase Alpha is savagely attacked and invaded! Then, having let them take Maya he makes a desperate attempt to save her....