The Moon approaches a solar system with two planets on opposites sides of its sun. The Alphans are trapped in an interplanetary conflict when warships from both worlds trespass on the Moon to fire missiles at their opponents' planets. After taking in a refugee from a destroyed gunship, the Alphans discover they have drifted into the middle of a literal war of the sexes.

The Alphans are visited by a bizarre spacecraft, whose request for supplies hides a deeper purpose. The ship, Gwent, is found to be sentient, the attempt of a vain alien genius to live forever. Powerful, unstable and craving companionship, Gwent intends for Koenig, Helena and Bergman to replace its aged, dying creator.

The automated Earth space probe Voyager One is approaching the Moon. With the radioactive exhaust from its engine certain to extinguish all life on Moonbase, the Alphans try to gain control and shut down the drive. Help comes when the probe's designer is found living on Alpha under an assumed name. However, Voyager is being followed by alien ships seeking revenge.

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.

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.

In September 1999, John Koenig reports to Earth's Space Research Centre at Moonbase Alpha as its new commander. A strange sickness is killing some of the Moonbase Alpha crew. Commander Koenig's investigation reveals that the source lies at Nuclear Waste Disposal Area 1 caused by excessive magnetic energy fields. The continuous build up of energy shortly causes massive explosion clusters that knocks the moon off orbit into deep space.

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...

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.

After an encounter with a space-time anomaly, the Alphans find their Moon back in the Solar System on a course to re-enter Earth orbit. The celebration ends when it becomes apparent Earth is an inhospitable wasteland. The mystery deepens when they discover a duplicate Moon already in orbit and a duplicate Moonbase Alpha lying empty and deserted.

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.

The wandering Moon suddenly changes course and comes to a halt in the vicinity of a dead world. As Alpha's power fails, the only hope for survival is to evacuate to the planet, which was ravaged by a nuclear war in the distant past. Searching for answers, a team is sent to the surface, where they discover the shocking truth of the origin of Mankind.

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.

The Alphans land on a planet seemingly devoid of any human existence but being run by a group of machines. The machines explain to the visitors that their human overlords are in a state of regeneration but the chief machine, the Guardian,sees the Alphans as posing a threat and it is down to two newly regenerated females known as A and B to decide their fates.

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.

A spaceship arrives on Moonbase Alpha carrying a prisoner, whom Maya is astonished to learn is Dorzak, a survivor from her planet, Psychon. But can he, a man of peace, really be guilty of the crimes of violence for which he is being exiled?

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....

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.

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.

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.

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.

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.

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.

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....

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.