A transmission from Dr. Logan in Texas City leads the Alphans to believe that they can finally land back on Earth, though they have travelled through time and, when they touch down in Texas City, they will be in the twenty-second century. However, due to a hitch, they find themselves in a barren and hostile environment. It is Scotland in the fourteenth century where the Scots are at war with the English invaders.

The expansive Taybor, an inter-galactic merchant arrives from hyper-space on his ship the 'Emporium'. He is offering to sell things to the Alphans. Koenig realizes that if the Taybor sold them his space-ship, it would enable the Alphans to fly back to Earth, but the price the Taybor is asking for this transaction is Maya.

Whilst he is exploring an asteroid Koenig is taken over by an alien race known as the Kalthon, who replace him with an exact double. In consequence every action ordered by the fake Koenig is solely for the benefit of the Kalthon and to the detriment of the welfare of the Alphans. Helena realizes that something is wrong when 'Koenig' is cold to the touch and needs to convince the other crew members.

Ship's engineer Patrick Osgood believes he can obtain titanium, to make a new heart for his sick wife Michelle, from the catacombs of the moon, using dynamite. The explosion which follows gives him a vision of the future in which the ship is pursued by a fireball and this comes true. Though Helena is making a new heart for Michelle, Osgood becomes impatient and drags his wife back into the catacombs, giving Koenig a double task - to avoid the fireball and save the Osgoods.

Koenig and Verdeschi are sucked into a space warp. A feverish Maya is stricken with a fever that causes her to transform into a repulsive space monster.

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...

People from Earth have landed on Moonbase Alpha, promising to take the Alphans back home. Commander Koenig, however, sees not fellow human beings, but aliens, and tries to kill some of them. Horrified, Helena stuns him with a laser gun and later, as he lies unconscious in the Medical Center, Koenig is approached by one of the aliens (for that is what they really are) who tries to smother him...