Approaching an inhabited planet, the Alphans are suddenly pounced upon by warships. In an unprovoked attack, Moonbase Alpha is devastated by Earth-style Hawk fighters. With 128 dead and Alpha unable to sustain life, Koenig and Helena appeal to the aliens for mercy. The aliens proclaim the Earthmen to be an invading virus, with no right to exist.

On a frozen planet, the Alphans encounter shipwrecked humans from a lost expedition. The expatriates from Earth enjoy an idyllic existence: they have been made immortal and have lived there for over 880 years. They invite the Alphans to join them in paradise, but dissidents reveal all is not at it seems, teaching Koenig that immortality comes with a price.

In 1996, Tony Cellini commanded a high-profile space mission which ended in disaster. The sole survivor, he told an outrageous tale of a spaceship graveyard and an alien 'dragon' which devoured his crew. Believed by no one, he was left a broken man. Five years later, the truth is revealed when the runaway Moon approaches the same deadly Sargasso in space.

The travelling Moon drifts within range of a black sun. Pulled toward certain destruction by its inescapable gravitational force, the Alphans employ desperate measures to stay alive. As a lifeboat Eagle carries six persons to safety, the Moon plunges into the black sun, with only an experimental forcefield protecting Alpha.

Strange events befuddle the Alphans as they approach the planet Piri. When exploring its lifeless surface, Koenig encounters the seductive servant of the mysterious Guardian of Piri. She offers the wayward Alphans a life of peace and perfection. Realising the deadly truth behind the peace of Piri, Koenig struggles to free his people from the Guardian's influence.

A lush Earth-type planet holds the promise of a new home for the people of Moonbase Alpha. When the reconnaissance Eagle returns, it carries an unexpected passenger: Helena's husband, who died five years ago. The mysterious Lee Russell tells the Alphans that death awaits them on the new planet. The Alphans ignore his warning and unknowingly descend into a world of antimatter.

An alien spacecraft crashlands on the Moon, its passengers refugees from a dying world. As their destination is Earth, they generously offer to take one person with them when they depart. The scheming Commissioner Simmonds takes steps to ensure that he is the lucky individual chosen, even if it means destroying Alpha.

Anonymous alien benfactors provide the wandering Moon with a breathable atmosphere. The Alphans rejoice as they realise they have a wonderful new home in their own backyard. Preparations are made to settle and begin building a new civilisation on the Moon's surface. Koenig is suspicious of the aliens' motives, wondering how long this generous gift will last.

An Eagle and its crew are crushed to death by an enormous energy field in space. When one of Alpha's astronauts is possessed by the anomaly, he tells them the energy field is a living space brain, which responded to the 'threat' with antibodies Finding the Moon on a collision course with the Brain, the Alphans make plans to avoid the same fate as the Eagle.

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.

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.

A sinister woman called Zamara materializes on the base, forcing Helena and Tony to accompany her to the planet of Vega, whose natives are anything but friendly. A servant of the Vegans, known only as Number Eight, informs the two Alphans that he and his race are the natural inhabitants of the planet and that Zamara and her race are androids, who, it turns out, want the Alphans to teach them warfare.

The tall and imposing Magus arrives on the base. He claims god-like powers, namely that he effected the Creation. But he is now disillusioned with the way that Life has progressed and wishes to start again. He plans to mate Helena and Tony and Maya with Koenig. But of course he is not God but a renegade cosmic sorcerer, and quite an illogical one at that, who needs to be controlled.

The latest extra-terrestials to be rescued by the Moon Alpha Base crew are Pasc and his young son Etrec. They are from the usually peaceful planet of Archaron and they claim that they are victims of a rebellion, engineered by Pasc's wife Lyra. However, Helena discovers that they have both been infected with a virus which makes them considerably less friendly and more deadly than their initial claim.

Several crew members explore the planet Sunin, including botanist Shermeen Williams, who appears to have visionary gifts. She links up with an alien, called Vindrus, who wants her help in transferring his body and that of his race, into solid matter, giving them proper human form so that they can join the universe as real matter. However, for every one of his race made flesh, an Alphan must lose their matter.

A pretty, young Alpha technician dies a horrible and unexplained death. Dr. Russell's experiments reveal that one of the crew is possessed of paranormal mental powers and is trying to take control of Moonbase Alpha....