[3][4] It is 2,409 days after leaving Earth orbit, and Moonbase Alpha is tracking an unidentified powered object following the Moon.
Sensors detect no life forms and the craft is emitting an energy field highly sensitive to matter.
As John Koenig orders defensive measures, the object projects a ray at Alpha that not only penetrates the defence screens but underground into Command Centre.
As attempts to contact the inert survey device fail, technicians examining Computer discover damage to its data-bank.
Sensors detect activity from the alien object—it is losing molecular cohesion, transforming into a gaseous mass of raw matter.
Knowing Maya's death would suit his ambitious nephew's desire to ascend to the throne, the Archon supports Varda's recommendation to employ diplomatic methods.
It is Varda, presenting her credentials; Koenig is angered by the attack on Maya and the Dorcon woman offers a gracious apology.
Alpha is at red alert; combat Eagles rise on the launch pads, laser batteries are deployed, non-combatants move to underground shelters and security forces guard the airlock stations.
She informs him Dorcons do not die in the manner of most humanoid races: their brain-stems cease to function at an advanced age.
Alpha's main batteries return fire but the laser beams bounce off the Dorcon ship's hull.
The man is disarmed but a desperate Maya pleads with Helena to use the weapon to kill her—if taken, the surgery will leave her nothing more than a living husk.
Maya is nowhere in sight (having disguised herself in the form of a co-worker) and Varda resorts to using the mind-probe ray to flush her out.
He orders Maya taken to the medical unit, where she is placed under a paralysing beam while the Imperial surgeon prepares for the brain-stem transfer.
As the Archon withdraws, the Commander is secured in a force-field until the meson converter's antimatter coils recharge; the attack has temporarily drained its power.
Malic contacts Varda, telling her the escaped alien commander has gone berserk, killing soldiers in his search for her.
When trapped in a blind alley with pursuers just around the corner, he pulls open a grille and hides in a ventilation duct.
After waking his uncle to gloat on the end of his reign, he activates a surgical instrument that projects an intense energy beam on the Archon's forehead.
The sociopathic youth enjoys watching his uncle beg for mercy as the beam slowly fries his brain.
Just then, Koenig jumps out of the air vent; in a scuffle, Maya transforms into a lizard beast to subdue Malic.
He removes the badge of office from his uncle and places the medallion around his own neck, mocking the corpse with a sarcastic salute.
Her dying move is to fire her own weapon at the meson converter, intentionally damaging the magnetic shield to expose the antimatter coils.
The insane Malic hysterically shouts for the converter to obey its Archon as the ship blows apart with a blast that seems to set space itself ablaze.
With much of the same scene structure and dialogue, several differences exist: (1) The script notes the title 'Archon' should be pronounced the same as 'march on' to avoid confusion with the episode title "The Mark of Archanon"; (2) Helena is relegated to the underground shelters with her patients before the attack and is not seen until the epilogue; (3) Maya transforms into a potted plant to hide from Varda and threatens to shoot herself with Verdeschi's gun when outed.
When left alone, Koenig and Helena reflect that 'What's in the past has gone...fate has played us some strange hands but we've won through in the end.
[5] The Dorcon vessel's sets were constructed out of pre-existing flats and set-dressings from previous episodes.
Attentive viewers would recognise actor Laurence Harrington (playing Stewart) from his previous role as Tom Jackson in "Journey to Where".
This instalment would fulfill first-season script editor Johnny Byrne's three-script commitment to producer Fred Freiberger.
After seeing his scripts "The Biological Soul" and "The Face of Eden" (later "The Metamorph" and "The Immunity Syndrome") extensively re-worked (for the worse by his reckoning) for new series format, he gave the man a 'Freddie Freiberger/Johnny Byrne' action adventure story which would revolve around Maya, but done in such a way she would be rendered helpless.