Inside a city a graduation ceremony is in progress. The two brightest students have been selected - Abu Gond and Vana Gond - to receive the highest honour a Gond can receive. They have become companions of the Krotons. Abu receives his gown, but another student - Thara - tries to prevent Vana for getting hers as Abu goes into the Krotons' chamber.
The TARDIS materialises outside on the planet's surface. Jamie and Zoe have bad feelings about the place - there is a smell of ozone and sulphur - but the Doctor is keen to explore, taking an umbrella against the heat of twin suns. There isn't much to see as the planet is very rocky and appears dead, until they come across a city. Jamie makes his way down side of a hill towards an entrance to the city. The Doctor and Zoe have to follow.
The entrance appears to be metal, but is covered in moss and lichen. Now the Doctor begins to have a bad feeling and suggests they get away. It is not the entrance to a building but to a machine. As they are about to leave the door opens and Abu staggers out. The Doctor, Jamie and Zoe watch from behind rocks as two gas jets appear and Abu is engulfed in deadly gas.
Inside the city Thara is still trying to convince his father, Selris, not to let the Krotons take Vana, even though it is the law of the Krotons that the top two students become companions. The Doctor, Jamie and Zoe have made their way into the city, and the Doctor announces his presence and is met by three Gonds. The Doctor tries to tell them about Abu's death, but the Gonds are suspicious of them and refuse to listen. As this is going on Thara realises he has no choice and has to let Vana go. Zoe realises Vana has a gown like Abu, and the Doctor tries to stop interrupt the ceremony.
The three Gonds try to restrain them, and Jamie decides to fight. He turns down the offer of an axe weapon, preferring to fight bare handed. Jamie disarms the Gond, but the delay means Vana goes in to the Gond chamber. Selris then demands to know who the Doctor, Jamie and Zoe are. The Doctor wants to know what is behind the door that Vana went through, and is told that is where the Krotons are. The Doctor wants to know how to open the door, and tells them he saw a Gond dressed like Vana come out and get vaporised. The Gonds back away when the realise that the Doctor, Jamie and Zoe have been outside - into the poisonous wasteland.
Zoe realises that if the same thing happens again Vana will be killed. The Doctor, Jamie and Zoe, along with Thara, head out into the wasteland. The Doctor jams in two rocks where the gas jets emerged, and when Vana staggers out the Doctor drags her out of the way before the gas jets emerge. Vana is almost completely catatonic. Jamie and Thara take Vana to Thara's father's house. Thara tells the Doctor that the Krotons have always been their friends, but seeing Vana makes him think differently. In the past many students have joined the Krotons, and as the gas dissolves the bodies it is possible they have all been murdered by the Krotons. When Zoe asks what they look like Selris says they have never come out. Legend says that silver men came from the sky. The Gonds attacked them, and the silver men made poisonous rain fall from the skies. There was a war, but the Gonds learned to live in peace with the Krotons. The Krotons even gave the Gonds learning machines that everyone uses. All the Gonds' knowledge and culture comes from the Krotons. Now that the Gonds know what happens to students that join the Krotons Selris is worried this may start a new war with the Krotons.
In the Learning Hall the Custodian is attacked by four Gonds, including Thara, who want to know more about the Krotons. As the servant of the Krotons he knows how to get to them, and the Gonds say they just want to see the Krotons for themselves. The Custodian says they never come out, not even at night. Thara says they must get the Krotons to come to them, and smashing the learning machines should do that. Inside the Krotons' chamber the damage to the learning machines has been reported. As Thara and the students prepare to smash more machines they hear a voice telling all Gonds to leave the hall. Selris has been given a message about what Thara was planning, and he, the Doctor, Jamie and Zoe cut through the wasteland. They get there in time to stop Thara and the students from smashing more machines. A probe emerges from the Kroton's chamber and heads for the Doctor, Jamie and Zoe, looking for the Doctor.
The Doctor moves out of the way and covers his face, confusing the probe. One of the students attacks the probe and is dissolved by gas. The probe, having killed, thinks it has completed its task and retracts. The voice once again tells everyone to leave the learning hall. Back at Selris's house the Doctor checks up on Vana, who is still unconscious. The Doctor is eager to have a look at the learning machines with Zoe. Selris insist on going with them. Jamie is left behind to look after Vana. In the learning hall the Doctor finds a trap door leading to an unused underhall. As the Doctor and Selris explore Zoe is left in the hall. She starts to use on the unbroken machines. When the Doctor and Selris return the Doctor is angry she has been using the machine. Zoe says the questions were easy, and she felt they wanted to see her. Zoe registers the highest score on the tests.
Back at Selris's house Vana awakes, but is traumatised by what she has seen, talking about burning in her head and flashing lights. Jamie gives here pills the Doctor had left, and as she rests goes to get the Doctor.
The Doctor and Zoe examine the door to the Krotons' chamber. It appears metal but is in fact crystalline. And underground the foundations appear to be more like a root structure, meaning the Krotons' chamber is organic. A gong sounds, and the Krotons send a message to Selris saying they have chosen Zoe as a companion. The Doctor doesn't want to let Zoe go in alone and decides to take the test himself to go in with her. The Doctor is panicking. Lacking concentration he makes mistakes on the tests. After calming down the Doctor starts to answer correctly. Soon afterwards the Krotons ask for Doctor Gond to join them, and both the Doctor and Zoe enter the chamber. Jamie arrives just in to see them go.
The Doctor and Zoe find themselves in a spaceship with no signs of any crew. There is a chair and they both sit down. Seeing a force chamber the Doctor tells Zoe to hold on to a chain to equalise the load as the force chamber starts to transfer mental power from them and into raw power. After they recover the Doctor and Zoe see a vat containing a solution of crystals in suspension. As something starts to form in the solution the Doctor takes a sample and he and Zoe run to a different area of the ship before the Krotons in the solution can fully form. The Doctor and Zoe find their way to the exit. They make their way outside and make their way back to the TARDIS.
The Krotons realise that the Doctor, Jamie and Zoe are not Gonds. Jamie is trying to break in, and the Krotons let him in for study. Once inside Jamie is caught by a Kroton and his mind is tested. Normally the machine would kill someone who not intelligent, but they spare Jamie for questioning about the Doctor and Zoe. Using a scanner the Krotons locate the TARDIS and see the Doctor and Zoe go inside. One of the Krotons leaves the spaceship - the Dynatrope - to fetch them back.
Inside Selris's house more Gonds are starting to talk about war against the Krotons. They try to get Beta, the Gond scientist, involved but he thinks that there is no way they can defeat the Krotons by themselves. After a vote Eelek takes over the council from Selris and promises revenge for the Gonds.
Inside the Dynatrope Jamie is learns that the Krotons need mental energy from the Gonds. The Gond energy is not sufficient, but the Doctor and Zoe have more that the Krotons need. The Kroton tells Jamie that Krotons cannot be killed. They can exhaust, a reversion to basic molecules, but after this they can be reanimated.
Outside in the wasteland the Doctor and Zoe emerge from the TARDIS after analysing the solution sample. The Krotons' life system is based on tellurium. The Doctor starts to collect samples of sulphur that are close to the TARDIS. Zoe thinks they are being watched, and looking round sees a Kroton. It order the Doctor and Zoe to return to the Dynatrope. Inside the Dynatrope Jamie attacks the other Kroton, causing the Kroton with the Doctor to loose its direction point. Seizing the chance the Doctor and Zoe run past it to a high up ledge. The first Kroton recovers. As the scanners can't locate the Doctor or Zoe it orders the other Kroton to destroy the TARDIS. When the Kroton fires the TARDIS disappears. As the Kroton starts to return to the Dynatrope the TARDIS re-materialises on a higher ledge. The Doctor tells Zoe that he had remembered to set the HADS (Hostile Action Displacement System) which means the TARDIS moves when threatened.
The Doctor and Zoe return to Selris's house to find Thara and a recovered Vana packing for evacuation. Thara tells the Doctor about Selris's plan to attack the Krotons from underneath. The Doctor asks Thara to take him to Beta. The Doctor gives the sulphur and some instructions to Beta. Zoe realises Jamie is missing, and the Doctor and Zoe go looking for him, thinking he may have tried to get into the Dynatrope.
Underground Selris is supervising the Gonds as they fasten chains round the foundations. As the Dynatrope begins to move the Krotons inside detect the imbalance. The Dynatrope is approaching exhaust time. The Doctor and Zoe go underground to try to stop Selris but the Doctor is caught by falling debris. Thara helps the Doctor, but is caught in a second fall, and his leg is fractured. The Dynatrope manages to stabilise, and the Krotons realise they have been attacked by the Gonds.
Vana arrives to give the Doctor a small bottle of the sulphuric acid he had asked Beta to make. Realising they still hadn't found Jamie they run back to the Dynatrope to find him. Inside Jamie manages to find his way to the exit, and outside the Doctor and Zoe help him to get away from the gas jets. The Doctor tells Jamie to go back to Beta and make more sulphuric acid.
In the learning hall Selris and Eelek are arguing as the Dynatrope opens and a Kroton emerges, asking for the Doctor and Zoe. The Kroton tells Eelek if he gives up the Doctor and Zoe the Krotons will leave. Not knowing Eelek's plan the Doctor and Zoe return to the learning hall, and are captured by Eelek and his men. As the Doctor and Zoe enter the Krotons prepare from take-off. As the door to the Dynatrope closes Selris, with the small bottle of acid, jumps inside. He is killed by a Kroton, but the Doctor has the small bottle of acid.
The Krotons tell the Doctor he must help them before the Dynatrope exhausts. If the Dynatrope does exhaust the energy released will kill everyone and most of the planet. The Doctor agrees to help, but needs to know what various bit do. The Krotons show the Doctor a transfer device that runs on mental power. It needs four high brains. Two Krotons are not enough, but with the Doctor and Zoe they have four high brains.
Back in the learning hall Thara and Jamie arrive with a vat of acid. Inside the Dynatrope the Doctor hands Zoe the bottle without the Krotons seeing, and then subtly telling her what to do by telling the Krotons he knows that if their solution vat was contaminated they would die. The sulphuric acid takes time to act, and the Doctor plays for time by procrastinating and pretending the Krotons are making him nervous. Soon afterwards the Krotons begin to moan in pain as they begin to dissolve into their basic form. The Dynatrope also begins to melt.
The Doctor and Zoe escape to the learning hall to find Jamie and Thara pouring the acid into the Dynatrope roots underground. Beta surmised that if the Doctor had asked for this much acid then it must have been for a reason, and the Dynatrope continues to dissolve, destroying the Krotons and freeing the Gonds from control.
Regular castJamie McCrimmon: Frazer Hines; Zoe Heriot: Wendy Padbury;
Guest castSelris: James Copeland; Vana: Madeleine Mills; Thara: Gilbert Wynne; Eelek: Philip Madoc (1,3,4); Axus: Richard Ireson (1,3,4); Beta: James Cairncross (1,3,4); Abu: Terence Brown (1); Student: Bronson Shaw (1); Custodian: Maurice Selwyn (1); Kroton Voices: Roy Skelton, Patrick Tull (2-4); Krotons: Robert La Bassiere (2-4); Miles Northover (2-4);
Uncredited cast: Gonds: Keith Ashton, Ronnie Chance, Roger Charles, Justine Elliott, Robert Haywood, Alex Hood, Nick Hunter, Mark Johnson, Patricia Matthews, David Melbourne, Reg Nardi, Peter Rann, Nick Rutter, Sylvia Steele, Wendy Wilson;
|BBC 1||228||Episode 1||Sat 28 December 1968||5:15 pm - 5:40 pm||9.0M||55th|
|BBC 1||229||Episode 2||Sat 4 January 1969||5:15 pm - 5:40 pm||8.4M||54th|
|BBC 1||230||Episode 3||Sat 11 January 1969||5:15 pm - 5:40 pm||7.5M||61st|
|BBC 1||231||Episode 4||Sat 18 January 1969||5:15 pm - 5:40 pm||7.1M||68th|
Repeats (on the BBC)
Ealing Television Film Studios; Lime Grove Studio D;
Bloopers and mistakes
This programme has no bloopers or mistakes. It's probably not perfect, just that they haven't been found or pointed out yet.
Notes and trivia
This story has no incidental music.
This programme has no other working titles, or they have not been yet been entered.