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...

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.

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.

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.

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.

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...

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.

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 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.

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.

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.

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.

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.

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.

Whilst Koenig and Maya are exploring a planet called Luton,which is lush in vegetation, she picks a flower and he helps himself to some fruit. As a result they are put on trial for murder by three talking trees, the Judges of Luton. The trial is by combat and the pair must face three aliens, one with superstrength, one which can render itself invisible and one which can teleport.

Some subterranean miners start chanting for a planet that will cause the Moon to pass through a nebula deadly to those living at Moonbase Alpha.

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.

When exploring a habitable planet, members of the Alphan survey party vanish without a trace. Are they the victims of an indigenous tribe of Stone Age humanoids? The mystery deepens when a dead caveman is found to have capped teeth. Others soon notice the primitive cave chief and his mate bear an uncanny resemblance to the missing John Koenig and Helena Russell.

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 Alpha Moonbase needs a rare ore known as Milgonite, which is detected on an extremely dry planet. Koenig leads a small landing force and discovers a glowing rock formation which comes alive and cuts off the party's links with the base. It is a trap - the planet needs water to survive and has lured the travellers there for the water in their bodies.

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.

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.

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.

A technician falls under an alien influence, accessing classified information before mysteriously dying. Soon after, the Moon is stopped in space by the powerful rays of an alien spacecraft. The aliens' only interest in Alpha is the data held in its computers, information they now plan to obtain through the possessed eyes of their next agent: Helena Russell.

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.

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.