
Everyone on Moonbase is electrified by the arrival of a spaceship from earth. Everyone, that is, except Commander Koenig. Where the others see long-lost friends and relatives, he sees hideous aliens, bent on taking over the Moonbase...
An Eagle is sent onto the surface of the planet Psychon, which has titanium, needed for repairs to the Alpha Base. It fails to return and is used by Psychon scientist Mentor as a bait with which to entice other members of the Alphan crew onto the planet. Mentor is building a computer but it will be fuelled by the living brains of humans, and he has his eye on those of the Alphan crew. Fortunately his daughter, the shape-shifting Maya, does not share her father's views and is on the side of the Alphans.
With Maya now a crew member the Alphans discover a young couple called Cantor and Zova who have been in suspended animation for some while. They claim that they are exiles from the planet Golos, following an invasion, and ask for the help of Alphan crew members to restore the planet to them. Helena and Tony accompany them to the planet Golos, where it is apparent that they are not the young innocents they appeared to be.