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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?[1]



While Commander Koenig is investigating some asteroids that show some potential for colonization, a ship transmitting the universal plague warning signal is detected as it changes course for Alpha. The Alphans receive a request for permission to land. Tony refuses. Sahala explains that one of her crew is dead and another injured. When Helena asks about the universal plague warning, Sahala assures her that the plague is contained, and the Alphans are in no danger of exposure. Tony grants her permission to land. After Helena confirms that there is no danger to Alpha, Sahala's injured crewmate, Yesta, is put on a travel tube bound for Medical Centre. En route, Helena asks how she was hurt. Sahala tells her that they were transporting a criminal to exile on Theselena, the furthest planet in the Croton system, when he escaped, and injured Yesta. They exit the travel tube. Sahala sees Maya, and for no discernable reason fires her stazer at her, putting her into stasis.

Act One[]

She is put in detention until Tony can come interview her. She says that she did it because Maya is a Psychon. As she tried to justify her actions, Tony got angrier, telling her that she would spend the rest of her life in detention if Maya did not pull through. He leaves Alan, who seems more sympathetic, to talk with her. Sahala tells him that a Psychon ship approached Norvah asking for refuge. They accepted them, but soon Dorzak began to incite, to violence, a people that had been peaceful for thousand of years. Alan Tells Sahala that Tony will not bend unless Maya recovers. She tells him that Crotons don't kill, and that she can bring Maya back. Sahala is brought to Medical Centre and successfully revives Maya, who, rightfully, is panicked at the site of her attacker.

Tony has Sahala returned to detention. He tells Maya that a Psychon ship did make it to their world, and tells her of the trouble that Sahala claims was caused at the hands of Dorzak. Maya knew Dorzak, and is certain she is lying. She asks Tony to let her see and speak to Dozrak, a man she remembers as peaceful, a poet and philosopher. Sahala says, to repay Alan's kindness, she must continue warning him just how dangerous Dorzak can be. She tells him how she came to need the Alphans help.

Even in stasis, Dorzak was able to take over Clea, who was on watch as Sahala and Yesta slept. Under his control, she released the force field on his cell, then shorted out their ship's long range communication systems before releasing him from stasis.

Yesta woke to find Clea in the arms of Dorzak. She used the stazer on Dorzak, and brought Clea a drink to help clear her head. As Yesta set the drink down, Clea, still under Dorzak's control, hit her in the head with a heavy object. Sahala woke for her watch to find Clea and Dorzak in stasis, and Yesta bleeding to death. Once revived, Clea was so overcome with guilt, she threw herself out into space. That was when Sahala set course for Alpha to seek help.

Tony sends for Sahala to get permission to board her vessel. Alan accompanies her. Sahala tries to warn them that reviving Dorzak is too dangerous, but Tony won't listen. Sahala knocks out a security guard and takes his stun gun.

Act Two[]

She directs them away from the entry port at gunpoint. As she moves to board her ship, Alan grabs the gun from her hand. Tony has her taken to detention, and boards the ship anyway. He finds a small object that doesn't fit with the general decor of the ship and decides to have it analyzed to determine it's use. Maya finds the control to open the chamber where Dorzak's cell is located. Helena, Tony, Alan, and Maya debate whether Sahala was telling the truth about Dorzak and the potential dangers of waking him. Helena is called to Medical Center to operate on Yesta. Maya convinces Tony to let her revive Dorzak as long as the force field stays up. Tony is called to speak to Yesta, who should be awake soon, to verify or refute Sahala's story. Dorzak wakes and asks Maya if he is to remain a prisoner. She tells him that he will be freed when Yesta confirms that Sahala is lying. Yesta wakes in Medical Centre as Sahala arrives. Yesta, under Dorzak's control becomes hysterical upon seeing Sahala, claiming that she killed Clea. Yesta dies moments later.

Act Three[]

Tony contacts Maya to tell her that Dorzak is innocent, and she may release the force field and give him better accommodations. Tony takes the device he found on the ship to be analyzed, and learns that it jams "organic psycho-waves". He is told there was a transmission at the time of Yesta's death. He tells Maya, and suggests that if Dorzak and "Sahala" were to be left alone, the truth would come out. Tony announces to the base that Sahala has kidnapped Helena, and is moving towards her ship. Dorzak hears, and offers to trade himself for Helena. "Sahala" contacts Command Center and demands a trade, stating she will ignite her ship's photon drive, killing everyone on Alpha if he does not accept her terms. Tony agrees and Dorzak is brought to the boarding tube attached to her ship. The exchange is made, and "Sahala" takes Dorzak into her ship. Maya learns that he is no longer the peaceful man she remembered. But not before he realizes that she is not Sahala. He forces her to change back.

Act Four[]

She asks if there is some flaw in the nature of Psychons that turn them into monsters, as she recalls her father's misdeeds. Dorzak claims that it is the struggle for survival that makes monsters of them all. Maya replies that the Alphans have not been warped by their struggle. He replies that they are a "pathetic example of the lingering process of extinction". He forces her to teach him the art of molecular transformation when she refuses to help him. Tony, Helena, and Alan, who have been waiting outside the airlock enter to make sure everything is ok. They find Maya standing outside the force field with Dorzak in stasis. She tells them that he was not the man she remembered.

Alan leaves to tell Sahala that she is free. Maya is clearly upset, and Tony tries to cheer her up by offering her some beer. She says she would love some. He then suggests they go for dinner afterward. She says yes, but wants to stay and apologize to Sahala first. Tony tries to gather everyone else to leave but Helena says she wants to learn about stasis from Sahala before she leaves. "Maya" tells her she has an operation she wants her to perform. Helena, clearly under the influence of "hypno-suggestion", agrees. Alan tells Sahala that she is free to go, and that Dorzak is back in stasis. She thanks him for his friendship, and they return to her ship.

Dr. Ed Spencer contacts Tony to tell him that Helena was acting oddly when she returned to Medical Center, and left with a surgical case without a word. Tony realizes something was wrong when Maya said she'd love some beer, and meets him in Medical Center. On Sahala's ship, Dorzak disarms Alan, and has Helena prepare to remove the device that protects Sahala from Dorzak's psychic control. Tony shows up, and Dorzak commands him to hand over his weapon. Tony moves towards Dorzak, and knocks the stun gun from his hand. Dorzak makes a run for the airlock, but Tony stuns him, releasing everyone under his power. Tony drops the force field, freeing Alan, and then releases Maya from stasis.


Helena removes the neuro-pulsonic jammer from Tony's head, as Alan sees Sahala off. She asks him how his species says goodbye. He shows her by kissing her. He asks how they say goodbye on Norvah. She replies his way is better.[2]


Chris Penfold wrote (probably) two drafts. The script was completely rewritten (by Fred Freiberger): Penfold says the only thing he recognised was his name on the cover. The overall story was the same so Penfold decided to keep his name on the episode.

Shooting script dated 4th August 1976. Revised 3 November 1976.

A "Double Up Helena" script, filmed simultaneously with Devil's Planet

Filmed Tuesday 2nd November- Tuesday 16th November 1976.

Jill Townsend was sick throughout filming, with suspected flu. It turned out to be appendicitis. She insisted on carrying on and having the operation after filming.[1]

International Titles[]

Country Title Translation
Belgium (Flemish) Dorzac
Spain Dorzak
France/Canada Dorzak
Germany (DVD) Gestaltenwandler Shape Changer
Italy Dorzak
Japan Dorzak, An Uninvited Guest
Portugal Dorzak



  • Int. Command Centre
  • Int. Medical Centre
  • Int. Detention
  • Int. Dorzak's Quarters
  • Int. Technical Lab
  • Int. Alpha Corridor
  • Int. Boarding Tube
  • Int. Croton ship[1]


The Croton ship was a Brian Johnson design, made by Martin Bower. One of the SFX crew put a lampshade on it as it made a good light stand.

The Croton ship lands in front of a large photo of Moonbase Alpha, not the actual model.

The forcefield was simply coloured perspex bars, removed by bump cuts.

The kaleidoscope patterns shown to Clea are also seen in The Taybor and New Adam New Eve.


Koenig is investigating "a belt of asteroids which give us some hope for colonisation". Living on an asteroid would be less hospitable than the Moon.

The Croton computer knows about Earth as it identifies the Moon.

"Organic pyscho-waves" sounds like the lambda variant in The Lambda Factor.

Tony requires surgery to insert and remove the neuro-pulsonic jammer capsule into his skull. How did Clea remove her own capsule?

Croton is an entire galaxy of planets including Norvah.

A photon drive usually means a laser pushing the ship (the slight pressure of photons against a large sail slowly increases the ship's speed). Presumably the large sails are retracted at this point and the ship is coasting.

An alternative type of photon drive is the use of electron-positron annihilation to produce thrust, first proposed by Eugene Sanger in 1953 in an article titled The Theory of Photon Rockets. The popular 1972 book The Challenge of the Stars by Patrick Moore and David Hardy featured a beautiful painting of a photon ship arriving at the Orion nebula. (Thanks to Jorge Luiz Calife).


Chronology: 2009 days after leaving Earth orbit (Mon 14 Mar 2005)

Alpha Personnel: 0 fatalities.

Alpha Technology: Medical thermographic scans are used. They are also featured in Breakaway, Matter of Life and Death, Ring Around the Moon, Another Time, Another Place, Missing Link, Force of Life and Space Warp.

Note the use of the silver decontamination suits (also seen on firemen in various year 2 episodes).

Eagles: None

Maya transformations: Sahala, Dorzak, white hamster

Planets: None

Aliens: Dorzak from Psychon; Sahala, Yesta and Clea from Norvah, all humanoid

Props: Dorzak's costume was reused from Mentor's costume in Space Warp. Yesta's costume was reused from Maurna's costume in The Mark of Archanon.


The perspex "forcefield" has a small gap visible bottom right. Thanks to Martin

Why does Helena have a space helmet with her anti-contamination suit? The stretcher-bearers do not. Thanks to Thomas


Croton is a Calabrian port, an important city colony of Magna Graecia founded by Myscellus in 710 BC. It was famous for its medical school and success at the Olympic Games. Between 530 and 510 BC the philosopher Pythagoras and 300 of his disciples settled in the city. There he founded a religious, political, and philosophical movement known as Pythagoreanism. The more dictatorial aspects of his ideas led to them being ousted by democratic government. The poet and philosopher Dorzak seems to be based on Pythagoras.

Ed Spencer's role was scripted to be Ben Vincent. The character was originally named Ed Spandau in the call sheets. Richard Le Parmentier is named Sam in the script and episode, but credited as Ed Malcolm (the name used in script revisions).

Alan's description about his Australian cattle ranch and surf boards is cut.

Another cut was Maya telling Dorzak about the gastronomic delights on Alpha (he tells her "You have become very Earthly, Maya")

Another cut was Sahala explaining to Alan why she did not mention the neural jammer. "It was my only protection from Dorzak's powers. I feared in your ignorance you would try to remove it from me and leave me vulnerable Yesta."

The scripted ending was cut, where Tony asks if the jammer can be adapted so he doesn't hear Maya's voice. She asserts she will stay by him until he recovers and changes into Dorzak.

Maya turns into a Guinea Pig with black spots. In the script this was a white mouse with zebra stripes.



Season 2
The Metamorph I The Exiles I One Moment of Humanity I All That Glisters I The Mark of Archanon I Journey to Where I The Taybor I The Rules of Luton I New Adam New Eve I Brian the Brain I Catacombs of the Moon I The AB Chrysalis I The Beta Cloud I Seed of Destruction I A Matter of Balance I Space Warp I The Bringers of Wonder - Part 1 I The Bringers of Wonder - Part 2 I Dorzak I The Seance Spectre I Devil's Planet I The Lambda Factor I The Immunity Syndrome I The Dorcons
Episodes are listed in the order suggested by Andrew Kearley.