The TARDIS materialises in what appears to be an alien jungle. Jago and Litefoot are excited about their first trip to a strange locale. But Jago is quick to complain about the tumultuous journey he endured in the TARDIS and wishes to never set foot inside again. Litefoot is quick to reprimand his friend as they still have a return journey to London. Jago presumes The Doctor has taken them to Borneo, Asia. But Litefoot corrects him as he has been to India and knows it’s sky isn’t purple. So, it isn’t Earth…The Doctor reveals to his companions that they have set foot on Venus and the tiny white dot in the sky is Earth. Jago quietly suggests to Litefoot that they should claim Venus in the name of the British Empire, but when Litefoot questions whether or not he has a British flag on his person, he dismisses the notion. Suddenly, an animalistic roar echoes through the jungle, and a huge rhinoceros like creature emerges from the bushes. The Doctor identifies it as a Shanghorn, a native lifeform. The Shanghorn suddenly becomes aggressive and charges through the jungle. The Doctor curiously states that the Shanghorn are usually quite passive, but this one is noticeably distressed. He wishes he had a musical instrument to calm it down as the Shanghorn can be pacified by music. The Shanghorn notices the trio and begins to chase after them until it is suddenly shot in the head by a laser weapon, incapacitating it. The trio hide in the shrubbery to determine the creature’s assailants. A ship touches down nearby and two Amazonian women clothed in alien skins and pelts, Vulpina and Felina emerge. Felina congratulates ‘her Highness’ for a spectacular shot and Vulpina fires another shot into the Shanghorn to confirm the kill. Vulpina orders Felina to transfer the corpse to her sky yacht. Litefoot is amazed to find intelligent life on another world, Jago on the other hand is amazed to find intelligent women. But The Doctor is furious that the women have murdered a defenceless creature in cold blood. Vulpina spots the trio, Felina asks if she would like them killed. But The Doctor declares there’s no need and surrenders willingly. Vulpina and Felina are fascinated by the new arrivals, theorising that they must be a new breed of ‘Thraskin’. Vulpina orders Felina to restrain them with a hunting mesh, she does so, and the trio are caught. Vulpina demands to speak with ‘the loud, colourful one’ about why he accused her of being a killer. The Doctor retorts the creature posed no threat to her, but Vulpina reveals the creature only an hour ago savaged her chief scientists to death. The Doctor doesn’t believe her, but before he can offer an explanation, Vulpina orders Felina to imprison them in her sky yacht. They’ll be taken to Amtor where they’ll be kept as hunting trophies…
On the yacht, Jago is quick to complain about their incarcerators, The Doctor tells him to look on the bright side: They’re still alive when they could’ve easily killed them. He’s lacking knowledge about the Venusians in this time period as the last time he met them was several centuries in the future during his second incarnation with Jamie Mc Crimmon and Victoria Waterfield. Jago suggests they try to find a way to escape, but The Doctor advises against it and tells them to look through the porthole. The trio look in awe at what appears to be a ginormous floating city suspended in the air by hot air balloons with factories littered as far as the eye can see – Amtor.
The Doctor, Jago and Litefoot are detained in a cage along with many other alien animals in a zoo – much to the distaste of Jago. Litefoot notices a group of man-sized lemurs sitting in the adjacent cage, The Doctor identifies them as Thraskins, which is strange as they shouldn’t be caged up and suspects something very wrong is going on. The cage guard orders The Doctor and Litefoot to come with her, and chains them together with manacles before escorting them away, leaving Jago alone, much to the supposed amusement of the animals he’s sharing the cage with.
The Doctor and Litefoot are led to a laboratory. The guard introduces herself as Ursina – the lead scientist of Amtor. Litefoot mistakes her for the chief scientist that was mentioned to have been killed by the aggressive Shanghorn. She corrects him by stating the deceased was the previous chief – Corvina. She reveals that she wants to examine them to ‘see what makes them tick’ and requires only a few bodily cells – so she extracts a saliva sample from each of their mouths. She reveals that it is her duty to catalogue all the species of the world. Litefoot corrects her by telling her that he and Jago are travellers from Earth, hence they are not native to Venus – they arrived on Venus via their own ship. Ursina finds this difficult to believe, as she casually states that Earth is classed as a dead world! The Doctor quietly reminds Litefoot that his TARDIS not only travels through space but time as well. They are on Venus in the distant future…
Jago attempts to befriend the captive Thraskins with a parlour trick involving a coin. What Jago doesn’t know is that he is being watched by Vulpina and Felina through a security camera. Vulpina takes interest in Jago’s trickery and commands Felina to have him brought to her.
Ursina explains that the Thraskins were at first believed to be savages, but some exhibit traits of rudimentary intelligence. The Doctor isn’t impressed by the fact that the Venusians use them as slave labour, while Ursina states that they don’t protest – in fact they seem to enjoy their menial tasks. Ursina reveals that Venus was once a desert world hence why the Venusians lived in the clouds, until six years ago when plant life such as the jungle began to spring up across the planet, followed by insect life and just recently, reptilian and arthropods began to appear. The Doctor is sceptical about the idea of creatures appearing essentially out of nowhere and asks if Corvina was alone before the Shanghorn attacked. Ursina confirms this. The Doctor further probes that if Corvina was alone when she died…who can say that the Shanghorn was the culprit? Ursina reveals the grizzly fact that the Shanghorn was discovered eating Corvina’s corpse. The Doctor isn’t convinced, because not only are the Shanghorn shy, placid creatures, they are strict vegetarians…Litefoot offers to examine Corvina’s remains to determine what truly caused Corvina’s death.
Jago is brought before Vulpina. He is quick to try and charm her, but she cuts to the chase and reveals that she has been watching his antics and demands to know why he was entertaining the Thraskins with his tricks. Jago states he was simply trying to pass the time, plus they seemed to enjoy his antics. Vulpina then orders Jago to entertain her the same way he entertained the Thraskins or risk being either sent back to the zoo or have his head mounted on her wall. Put on the spot, Jago presents the Empress with a riddle ‘What’s the difference between Joan of Arc and an oak tree?’ Felina enters and informs Vulpina of the affairs concerning The Doctor, Jago and Ursina. Jago provides the answer as ‘One is maid of Orleans; the other is made of wood’. Vulpina requests an explanation of the answer, but before Jago can do so, Vulpina turns her attention to a security monitor observing The Doctor, Jago and Ursina carrying out an autopsy on Corvina’s corpse…
Litefoot concludes his autopsy and declares that Corvina wasn’t killed by a Shanghorn. The bite marks on her body were inflicted after she died, in fact the Shanghorn only took a small sampling bite and left her alone afterwards. He shows a scorch mark on her body and deduces it to be the cause of death, and he and The Doctor know they’ve seen a weapon that can inflict such injuries quite recently…
Vulpina angrily demands Felina to lead a squad of soldiers to the lab and execute Ursina for treason, and have The Doctor and Litefoot killed as well, much to Jago’s horrified pleas. Vulpina concludes that they now know too much and threatens to kill Jago for protesting against her wishes. Jago begs Vulpina to spare him, she surprisingly does so…as long as he becomes her pet…
The Doctor suspects that Vulpina had Corvina killed, as Corvina had discovered the truth about the origin of the new life sprouting across Venus. Corvina’s theory was the new lifeforms were a biproduct from a change in the atmosphere due to the oxygen pollution from Amtor’s factories – the factories pump oxygen into Venus’ atmosphere. The Doctor presses Ursina for anything that may have Vulpina warranting Corvina’s death. Ursina realises that Corvina had a theory about a location called ‘The Forbidden Caves’ being the source of the new lifeforms. Before she died, she was planning an expedition to the caves. Ursina further reveals that Vulpina had decreed that anyone who set foot in the caves would be immediately executed…
Jago desperately shouts at the monitor for The Doctor and Litefoot to run, as Felina’s Royal Guards are closing in. Vulpina amusedly tells Jago they can’t hear him. Felina radios to Vulpina that they are converging on the lab, and she’s instructed her men to shoot on sight. Desperate to warn his friends, Jago randomly begins to press buttons on the monitor until he manages to activate a loudspeaker system, he shouts for The Doctor and Litefoot to run as the guards are closing in on them. Before he can say more, a loud thud is heard over the system. Jago has been knocked out by Vulpina. The Doctor and Litefoot wisely decide to heed their companion’s warning, much to Ursina’s disbelief. She knows an escape route through the zoo they can use to get free. But before they make their escape, The Doctor requests that she removes the manacles binding him and Litefoot together.
Vulpina has been watching the lab, and coldly remarks that her chief scientist will die for her treachery…She instructs Felina to ambush the group in the zoo.
The Doctor sets a trap in the zoo by opening the cage of the Venusian Spore Beetles, hoping that they will sting their pursuers with their paralyzing venom, so they have time to escape. Felina and her squad as predicted fall prey to the trap and the group manage to escape.
Jago watches in delight as his friends manage to get away, but Vulpina is less than amused. She radios Felina and demands her to prepare her sky yacht. Now they know where they are headed, she’ll persue them herself…and Jago will come with her…
On Ursina’s yacht, Ursina warns the Doctor that another sky yacht has launched from Amtor. The Doctor knows its Vulpina in hot pursuit, but Ursina reassures the group they should make it to the caves first. Ursina’s DNA genetic decoder (the device she used to get saliva samples from The Doctor and Litefoot) beeps to confirm it’s finished its analysis. She looks at her device visibly perplexed by the results. The Doctor’s results confirm he’s extra-terrestrial, but Litefoot’s results assert that he is Venusian! The Doctor makes a shocking deduction, the Venusians are descended from Humans! The Doctor explains that after Earth became uninhabitable due to lack of resources, humans had to flee the planet and look for a new homeworld - Venus. Unfortunately for humanity, they found that Venus’ atmosphere wasn’t hospitable for human life. In a desperate attempt at survival, the humans genetically modified themselves to evolve to the planet’s atmosphere, hence the new eyes, ears, lungs and…green fur.
On Vulpina’s yacht, Vulpina asks Jago if humans are just like him on Earth. Jago, a man of the Victorian era, makes a thinly-veiled comment that he is of the finer specimens (i.e. a man). He asks if Venus has men, to which Vulpina confirms but they are little more parasitic breeding stock to reproduce more Venusians until they grow old and die, much to Jago’s shock. Vulpina offers to introduce Jago to her husband. She lifts up her fur dress to reveal a small round creature the size of a pomegranate mumbling on her stomach…
While walking through the jungle, Ursina questions what the factories have to do with Venusians being the descends of humans. The Doctor answers that the humans were trying to change the atmosphere, so it was breathable for humans. They arrive at the Forbidden Caves and walk into the entrance. Litefoot notes that the cave is shaped like a Persian rug rolled up. The Doctor agrees that it does look more artificial than natural – implying that the caves were made for a purpose. And the only way they’ll find out is if they venture inside…
Felina informs Vulpina that they are approaching Ursina’s sky yacht, but nobody is on board and she deduces that they are approaching the caves on foot. Vulpina orders her to set the yacht down and inform the guards that they are going on another hunt…
The Doctor, Litefoot and Ursina find a large open space inside the caves, where they find walls made of an ice like substance with creatures frozen inside! They’ve found a clue to where the new specimens have been emerging from. A laser shot rings out and narrowly misses the group. Vulpina enters the caves and warns them it was a warning shot. Ursina angrily calls Vulpina an unfit empress and accuses her of murdering Corvina. Vulpina admits to her murder, and she’ll do the same to traitors. She orders Felina to eradicate the trio, but before she and her guards open fire, Jago runs out in front and stands between them and The Doctor’s group. Vulpina warns him to stand aside before she chooses to kill him too. The ice containing the creatures begin to shimmer and a forcefield suddenly pops up, separating The Doctor and Ursina from Felina’s squad, unfortunately Jago and Litefoot are still in the grasps of Felina’s men. Vulpina begins to panic and orders a retreat, but not before ordering Felina to seize Jago and Litefoot. Ursina is puzzled as to why she is leaving with the prisoners rather than killing them. The Doctor assumes she needs them alive for something. Whatever it was, something has Vulpina scared…Ursina directs The Doctor’s attention to something. A polite sounding voice addresses them ‘Welcome to the last resting place of the Cytherians’
Once outside the cave, Vulpina instructs Felina to have her guards place explosives around the cave entrance – she plans to seal it off once and for all. Litefoot protests the idea as The Doctor and Ursina will be buried, but Vulpina doesn’t care – it’s a fitting fate for traitors. She forces Jago and Litefoot to help place explosives, otherwise they will be shot for treachery.
The shrivelled-up, ape like creature identifies itself as Vepaja - a Cytherian, and they were the original inhabitants of Venus. The Doctor deduces that they made the caves. Vepaja explains that they weren’t very good at managing their planet’s ecosystem, as they used too much carbon dioxide that eventually rendered Cytheria (The Cytherian’s name for Venus) uninhabitable – creating storms and acid rain. They thus placed themselves in suspended animation to hopefully awaken at a time when the planet’s ecosystem becomes habitable again, along with samples of plants and animals so that they can effectively restart from scratch. And their young have started to walk on the surface of Venus once more. Ursina comes to a horrifying conclusion, the Cytherians are Thraskins, and the Thraskin children Vepaja mentions are the slave labour the Venusians have been using!
Under duress, Jago and Litefoot begin to lay down the explosives in the cave entrance. Jago apologises to Litefoot for their predicament, claiming it to his own fault. But Litefoot rebuffs his friend’s apology as he came of his own volition and is rather enjoying their adventure – plus they’ve got a story and a half to tell Ellie and Quick when they return. They both notice more of the crystal-like substance poking through the ceiling. Felina calls from the entrance they are to place the charges or die. Jago passes Litefoot a small pebble as he theorises that from where the Venusians are standing, they can’t tell the difference. He has a rather cunning plan…
Vepaja states the Cytherians intended to educate the young Thraskins when they had matured, but they were taken by Vulpina. She was the first to encounter the Cytherians and promised to help them, but she betrayed them instead. Vepaja then reveals that he is in fact a psychic collective of the greatest Cytherian minds, one that could act as a teacher and ambassador. Ursina reminds The Doctor of Vulpina, who has been waiting outside the caves…
Felina confirms that explosive charges have been placed around the cave entrance. Without further delay, Vulpina demands the explosives be detonated, but Jago sheepishly reveals that in his work – he misplaced one of the explosives. He immediately reveals that he has it in his mouth! As Jago cannot speak with the bomb in his mouth, Litefoot explains to the Empress and her cohorts that if they don’t do as they say, Jago will detonate the bomb and kill everyone with him. Vulpina sees his bluff and raises hers - Jago will hand over the explosive or Felina’s guards will execute Litefoot. Vulpina believes that Jago doesn’t have the courage to sacrifice himself to save everyone, even going as far as offering Jago to take her life if he can…Jago relents at the challenge and begrudgingly hands the explosive to Felina. They watch on sorrowfully as Vulpina laughs maniacally as the explosives are finally detonated, burying the cave entrance with The Doctor and Ursina inside…
The cave begins to come down around The Doctor and Ursina as the explosives detonate. Vepaja saves them by creating a forcefield to protect them from the debris, but they are trapped inside the caves. Vepaja begins to panic and reveals that the collective consciousness of the Cytherians believe this attack to be an act of war and he is sorry for what he is about to do. He shows a projection of Amtor and using his psychic abilities conjures a storm that destroys the elevation balloons keeping the city afloat. The Doctor and Ursina try to reason with Vepaja, stating that there are innocent people in the city and he can help find a way for both Cytherians and Venusians to coexist peacefully, but Vepaja is beyond reason…now is the time for war!
Vulpina demands Felina to return her to Amtor immediately as the storm rages around them. Felina is hesitant as lightning may strike their ship, but Vulpina doesn’t listen and threatens to kill her if she doesn’t obey. They notice that Amtor is beginning to fall out of the sky. Vulpina angrily let’s slip that Vepaja is punishing her for betraying him. Felina is horrified that her Empress is responsible for all of the misfortune happening around them, but Vulpina is dismissive and threatens swift retaliation upon Vepaja…
The Doctor angrily states that because of Vepaja, thousands of innocent lives will be lost. But Vepaja responds by stating that Amtor still holds the Thraskins. The Venusian jungle trees will cushion the impact of the city crashing into the planet, preserving any life on board. Vepaja reveals that the Cytherians will take revenge on the Venusians for enslaving their children and hunting their wildlife for sport. The Doctor deduces that Vepaja has psychic control over the Shanghorns, and he is sending a stampede of them to the city to kill any survivors!
Amtor crashes into the planet in a colossal cloud of smoke. From the sky yacht, Felina confirms that the city is mostly intact. Vulpina requests she set them down beside the palace, as she has to reassure her public. Jago dismays over the death of The Doctor, and if the Venusians don’t kill them, they’ll be playthings for Vulpina. Litefoot notices something outside the window and insists Jago to look as well – thousands of Shanghorns are rampaging towards the city!
Vepaja confirms that the Shanghorns have surrounded the city, all that’s left is the command to rampage through the city and kill everyone in sight. The Doctor knows that Vepaja is beyond reason, but instead asks for a favour. Vulpina has his friends Jago and Litefoot in the city, and he asks that he may speak with them one last time before they are undoubtedly killed in the ensuing carnage. Vepaja agrees to allow him to talk with the two gentlemen.
Felina reports to Vulpina, stating that Amtor’s guards have tried to kill off the Shanghorns to no avail. Vulpina commands that she and her guards are to stand outside and prevent them from breaching the throne room. Felina notes that will result in their deaths, but Vulpina rebukes her for not willing to lay down her life for her empress. With her faith in Vulpina finally broken, Felina aims her rifle at Vulpina, but she is defiant and threatens to have her eradicated for her treachery. But Felina reveals that the guards feel the same way she does, and demands they escort Vulpina to the royal chambers and have her imprisoned there – much to Vulpina’s shock. Felina addresses Jago and Litefoot, stating that they have no quarrel with them and they are free to leave. The Doctor’s voice suddenly sounds through the P.A. system of Amtor. Jago and Litefoot are overjoyed to discover The Doctor is still alive. The Doctor immediately apologises to the two gentlemen and he should have never brought them here. He bids them farewell but before signing off, he tells them if they plan to die…go out on a song! Litefoot realises that The Doctor was trying to tell them something and remembers the Shanghorns can be put to sleep with music. Felina is confused as Venusians don’t have any concept of music, much to the confusion of Jago and Litefoot. Litefoot realises that the two of them now have to put on the performance of their lives in order to pacify the Shanghorns – the two of them will have to sing! Felina grants the two men use of the P.A. system in order to amplify their voices so the hordes of Shanghorns can hear it. Unfortunately, Jago doesn’t know any appropriate songs…and they’d better be quick as the Shanghorns could rampage any second. Without any time left, Jago begins to sing God Rest Ye Merry, Gentlemen. Felina is amazed, the singing is working. She begs the two to continue their ‘strange noises’. The Shanghorns begin to slow down and fall asleep.
Vepaja is incredulous. The Doctor reveals that the Venusians have discovered a way to stop the Shanghorns and that declaring war is fruitless now. He appeals to Vepaja once more to reconsider his plans, as no doubt the Venusians will retaliate for the damage done to their city. This is a second chance to try and make amends. Ursina agrees to vouch for Vepaja. Vepaja agrees to the terms and wants to apologise to the Venusians for the Cytherian’s actions. Ursina apologises in turn for mistreating the Thraskins and promises to release them into the wild. With all the disputes settled, The Doctor asks they now try and find a way out of the caves.
Litefoot is feeding the Shanghorns some of the jungle vegetation. He muses about the idea of keeping one as a pet, much to Jago’s vexation. With the Venusians now living on the surface of Venus rather than on Amtor, Ursina tells The Doctor that with the jungle’s natural produce – they no longer need the oxygen factories and now dedicate themselves to furthering Cytherian science. The two species now have an understanding. The Cytherians will help to expand the knowledge of the Venusians, and the Venusians will help to raise the Thraskins. As for Vulpina, she is kept inside the cages of the unused zoo as a pet. But without a zoo, Jago and Litefoot ask Ursina what she will do now as she is effectively without a job. She isn’t worried as she plans to pursue the art of music. The group eventually reach the TARDIS. Ursina isn’t so sure about this blue box, but The Doctor assures her that looks can be deceiving! The trio bid Ursina goodbye and prepare to enter the TARDIS. Jago asks where they plan to go next, as he is feeling rather thirsty after their adventure and requests they head for the nearest public libation or pub. The Doctor is rather taken aback by the request. With the possibilities of space and time at their disposal, all they want to do is go to a pub? Luckily, he knows of a such a place, where the food and drinks are to die for! The Red Tavern!
The TARDIS materialises and the trio step out onto what appears to be a beach. Jago and Litefoot are rather confused, and The Doctor tells them not to tell him that it isn’t a pub. Jago decides that they should all get a portion of chips. The Doctor isn’t sure that it will be possible, as they’ve landed in the 1590s, years before the fried potato or the paper bag. Before they can figure out where they are, they hear a group of men aggressively pointing them out and approaching them fast. Before they can run back inside, a man drops down from the top of the TARDIS between them and the doors. Before they can be surrounded, Henry makes a run for it but The Doctor and Litefoot aren’t so lucky and are captured. The leader of the group approaches them and claims them to be filthy Englishmen who have come to deceive them like the other group of Englishmen. But soon they’ll share their fate…in the grave!
