Part 1 While flying an Eagle, Commander Koenig takes leave of his senses and starts performing daredevil stunts near Moonbase Alpha's atomic waste domes. Controller Verdeschi fears that a crash will cause a nuclear explosion. Koenig hits a dome and suffers grave
concussion. Arriving in a rescue Eagle, Captain Carter and scientists Bartlett and Ehrlich retrieve Koenig and return him to Alpha. Dr Russell places Koenig in an experimental neuromedical device – the Ellendorf Quadrographic Brain Complex – to prevent coma. Alpha's sensors detect a vessel approaching faster than the
speed of light. It is a Superswift, an Earth ship theoretically capable of
interstellar travel. Its appearance surprises the Alphans, who understood that the Superswift project had been cancelled. They are even more shocked when the vessel lands and the crew reveal themselves to be long-lost family and friends. The captain, Guido, is Verdeschi's brother. Russell embraces Dr Shaw, her mentor from medical school. Sandra Benes and Dr Vincent are reunited with their fiancés, Peter and Louisa. Bartlett greets fellow scientist Professor Hunter. The new arrivals are an advance party; transport ships are en route to take the Alphans back to Earth, which at
faster-than-light (FTL) speeds is just hours away. Peter and Hunter slip away to Medical and psychically manipulate an orderly, Sandstrom, into sabotaging the device treating Koenig. Seeing this over a video monitor, Vincent forces Sandstrom away, though he is briefly detained by the mental control of Louisa, which puts him in a trance. Russell sedates Sandstrom. Koenig awakes with no memory of recent events. When he sees the Earth visitors, he reacts violently, perceiving them as terrifying alien creatures. Russell is forced to stun him with her laser sidearm. Shaw scolds Louisa for failing to restrain Vincent, which has allowed Koenig to live. Louisa asks Shaw why their group fears Koenig when they could just manipulate him like the others. Shaw says that something is blocking their psychic link to him. Guido and Shaw work together to take over Kander, a records clerk with a resistant mind. Finally succumbing to the aliens' control, he is compelled to start a fire and is consumed by the flames. As the Alphans extinguish the fire, Guido and Shaw tell Verdeschi that he must dispatch a return party before the Moon's course takes it out of range of Earth. They manipulate Verdeschi into choosing Carter, Bartlett and Ehrlich for the mission. The three men depart in an Eagle, imagining it to have been upgraded for FTL travel. However, their destination is not Earth, but the waste domes. Shaw enters medical and begins to smother the defenceless Koenig.
Part 2 Shaw's attempt to kill Koenig is thwarted by the arrival of Maya and Russell. Koenig realises that his crashing the Eagle was the aliens' first attempt to kill him through mind control. He speculates that as the only person treated with the Ellendorf device, he has a unique perception of what is happening that allows him to see the visitors for what they really are. He tries to convince the other Alphans that the visitors cannot be who they appear – they are projecting disguises based on the Alphans' memories. Furthermore, considering
time dilation, any FTL journey to the Moon would equate to centuries on Earth, meaning that their real family and friends are long dead. Maya completes an Ellendorf session and gains the ability to see the aliens. Transforming into one of them to learn their motives, she discovers that they absorb radiation to sustain themselves. The radioactivity of their planet has been exhausted and they are searching for a new supply, obtainable by blowing up Alpha's
atomic waste domes. As they have low
kinetic energy, they must use illusions to trick the Alphans into performing the act themselves. At the domes, Carter and Ehrlich procure an atomic fuel core as a catalyst for the nuclear explosion. Koenig, Maya and Russell stall them by remotely locking them inside the fuel storage facility. To break the alien's hold over the Alphans, the trio blast
white noise over the Moonbase's public address system. Their true forms revealed, the aliens vanish. However, they are not defeated. Carter and Ehrlich cut through the lock and proceed to the domes in a Moon buggy, under the illusion that they are back on Earth partaking in leisure activities. Koenig, Maya and Verdeschi take off in an Eagle to stop them. Realising that the aliens are now focusing on Carter and his accomplices, Koenig has all of Alpha's non-vital systems shut down to deprive the aliens of
electromagnetic radiation. As there is electrical activity in the human brain, he also has anaesthetic gas released into the ventilation system to render the personnel unconscious. The Eagle crew catch up with Carter, Ehrlich and Bartlett. In the ensuing struggle, Ehrlich's spacesuit is breached and he is evacuated to Alpha. Carter and Bartlett are about to force the fuel core into the storage chamber when Koenig tackles Carter and Bartlett breaks free of the aliens' control. The alien leader appears, admitting that its people deceived the Alphans but asking whether their struggle to survive in space is truly preferable to the joys that the aliens offered them. Carter, still under control, tries to set off the explosion but is thwarted by Koenig. As the alien leader curses Koenig for condemning the Alphans to a futile existence, the aliens and their spacecraft vanish for good. ==Regular cast==