TARDIS Index File

The Krotons (TV story)

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The Krotons
Krotons title
Novelised as: The Krotons
Doctor: Second Doctor
Companion(s): Jamie, Zoe
Main enemy: Krotons, Eelek
Main setting: Gond planet
Key crew
Writer: Robert Holmes
Director: David Maloney
Producer: Peter Bryant
Release details
Story number: 47
Number of episodes: 4
Season/series: Season 6
Premiere broadcast: 28 December 1968 - 18 January 1969
Premiere network: BBC1
Format: 4x25-minute episodes
Production code: WW
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Official trailer
Doctor Who - The Krotons - DVD trailer01:19

Doctor Who - The Krotons - DVD trailer

Memorable moment
Great Jumping Gobstoppers! - The Krotons - Doctor Who - BBC03:51

Great Jumping Gobstoppers! - The Krotons - Doctor Who - BBC

The Krotons was the fourth story of Season 6 of Doctor Who. It was the first story penned by future script editor Robert Holmes, whose prolific contributions to the series would create or contribute to many key elements of the programme's mythology.

Synopsis Edit

The TARDIS arrives on the unnamed planet of the Gonds, who are ruled and taught in a form of self-perpetuating slavery by the alien Krotons — crystalline beings whose ship, the Dynatrope, crash-landed there thousands of years earlier after being damaged in a space battle.

The Krotons are in suspended animation, in a crystalline slurry form, awaiting a time when they can be reconstituted by absorption of mental energy. Periodically, the two most brilliant Gond students are received into the Dynatrope, nominally to become "companions of the Krotons", but in truth to have their mental energy drained, after which they are killed.

When the Second Doctor and Zoe take the students' test, their mental power is sufficient to reanimate the Krotons. The Doctor discovers that their life system is based on tellurium. With help from the Gond scientist Beta, he destroys them and their ship with an impure form of sulphuric acid.

Plot Edit

Episode one Edit

On the planet of the Gonds, a ceremony is underway. The two brightest students, Abu and Vana, have been selected to become "companions" of the Gonds' unseen masters, the Krotons. As Abu eagerly dons his selection robes and enters the Krotons' machine, Thara objects desperately begs Vana not to go. The Gonds argue with him. She has been selected for the highest honour. Those companions who have gone before have never been seen nor heard from again. The Gond leader Selris, Thara's father, is resolute, stating that Kroton law dictates that she must.

The Doctor's TARDIS lands in a desolate area nearby. Jamie immediately notes the strong odour of sulphur whilst the Doctor states that the planet has twin suns. Zoe suggests that they depart, but the Doctor opts to explore. From a clifftop they see the Gond city below. They encounter a metallic crystalline structure with a hatchway similar to the one in the city. Jamie noticed that the smell is stronger. The Doctor is cautious. He identifies the structure as a machine and wants to head back to the TARDIS. As they head off the door opens and they hide as a dazed and weary Abu emerges from the hatchway. Before their horrified eyes, he is evaporated by blasts of energy.


Jamie and Zoe are less than impressed by the Doctor's sunny outlook for their landing spot.

Thara and Selris argue over Vana’s selection. Thara questions if the Krotons even exist. Thara draws a weapon and is soon surrounded by Gonds. The Doctor, Jamie and Zoe enter the city. They are regarded with suspicion; the Gonds have never met strangers before and the area where they landed, the Wasteland, is believed uninhabitable. Meanwhile the stand off between Thara and the Gonds continue. Vana wants to go through the door in order to protect Thara. He relents. The Doctor, Jamie and Zoe watch this and the Doctor tries to stop it, thinking it some kind of sacrifice. The Gonds seize the Doctor and his colleagues for stopping their ritual. As a particularly hotheaded young man named Axus fights with Jamie, Vana rushes into the Kroton machine. Jamie wins the fight with Axus. Selris interrogates the Doctor and his colleagues. The Doctor’s description of the death of Abu shocks the crowd. As does the revelation that they have been in the Wasteland. The Doctor, Jamie and Zoe rush back to the Wasteland to rescue Vana, followed by Thara.

They all reach the door. The Doctor sets about finding stones and starts blocking the energy beams with rocks. They hide. Soon Vana appears and swoons. The Doctor swoops in with his umbrella up to save her. The gas knocks the stones free which causes the Doctor's umbrella to disintegrate but everyone is safe. Vana is near-catatonic. They all set off for Selris' house. Back in the city, the Doctor tends to Vana through hypnosis. Selris tries to make sense of what is happening. Have they always been murdering the selected Gonds. The Krotons, he says, have not been seen for thousands of years.The Kroton machine landed on the planet thousands of years earlier and the ensuing war nearly annihilated the Gonds and ruined the landscape. Since then, the Krotons have never left their machine.

Thara and a band of students sneak into the Learning Hall and interrogate the Curator for information about the Krotons. The Curator states he is forbidden to tell and that they only communicate through messages and, very occasionally, voice. They decide to fetch the Krotons out by smashing their teaching machines.

The Doctor and his colleagues learn that the Krotons created the teaching machines to train the Gonds on the laws, science and culture that require their top students to become companions; the Doctor notes this is a form of self-perpetuating slavery. Selris panics about what this means for his society. Beta, their chief scientist, arrives and tells Selris of Thara's actions. Selris worries he will not reach the Learning Hall in time; however the Doctor states that they can cross through the Wasteland. Selris is reluctant but soon relents.

Thara and his gang vandalise the Kroton teaching machines to force them to emerge. They are stopped by a bellowing, mechanical voice ordering them to leave the hall. Thara wants to push on to bring the Krotons out. The Doctor, Selris and everyone else arrive and unarm the vandals and reason with them.

Somewhere inside the machine, a check is run on the Doctor.

In the Learning Hall a portal opens and a metallic, snake-like object emerges and moves towards the group.

Inside the machine all screens display an image of the Doctor.

The probe homes in on the Doctor who backs away. The Doctor falls and covers his face as the machine bears in...

Episode two Edit


The Krotons take notice of the Doctor.

The device stops when the Doctor shields his face. Zoe notes that the device must use pattern recognition. This is confirmed when the Doctor deliberately lowers his hands momentarily and it comes back to life. A student attacks the device, which vaporises him and then retracts into the Kroton machine. The Doctor notes the apparently limited logic of the device's programming; it seems to think it has completed its task of destroying him. Thara wants to continue destroying the machines but Selris stops him. The bellowing mechanical voice returns, ordering them to leave the hall. Selris orders the Gonds back.

The Doctor checks up on Vana. She is getting better. The Doctor and Zoe note the large gaps in the Gonds' knowledge. They have a great knowledge of chemistry and medicine but no knowledge of electricity. The Krotons apparently are training the Gonds for a specific purpose. They leave Jamie to care for Vana to go and look round the Learning Hall. Selris says he will come with them.

The Doctor, Zoe and Selris enter the Learning Hall. The Doctor investigates a closed-off chamber running under the Kroton machine and he and Selris go to investigate. Left alone, Zoe's curiosity forces her to experiment with the learning machines. She becomes enthralled as she operates it. The Doctor and Selris come back saying it is only the foundations of the machine; however the Doctor has noticed something is peculiar. Before he has a chance to explain what he notices Zoe on the machine and pulls her off it and berates her. Zoe has a big smile on her face and says that the Krotons are happy with her. The Doctor tries to snap her out of this brainwashed state. Selris notices that she has registered twice as high as the record for a Gond score.

Vana wakes up. She begins to babble about a "burning ball." Thara tries to calm her but she continues to talk about "flashing lights" and her "burning mind." She briefly recognises Thara but then goes back into her reverie. Jamie gives her some pills the Doctor gave him which send her back to sleep. Jamie leaves to tell the Doctor of the situation.

The Doctor and Zoe are inspecting one of the walls in the Gond city and find it covered in some kind of crystalline substance. The Doctor states that underground he found that the machine's foundation had a root structure; suggesting the Kroton machine may be organic. A gong sounds and a message from the Krotons is delivered. Zoe has been summoned to be a companion of the Krotons. The Doctor takes the test himself so as to accompany her. He does not perform as well as Zoe; scoring higher but requiring more questions. The Doctor comes away from the machine stating that he is happy he has pleased the Krotons; before realising he too is becoming brainwashed. The gong sounds again and the Doctor has been summoned also. The door opens. The Doctor and Zoe have lost a bit of their bravery but edge their way in. As the door closes, Jamie enters and sees his two friends enter the dangerous machine.


Zoe and the Doctor inside the teaching machine.

The Doctor and Jamie find the interior chamber empty, save for two chairs. They sit and are subjected to a force generator that keeps the, glued to the spot. The Doctor asks Zoe to hold onto the other end of a chain which may equalise the power load and save them. The machine lights up and bears down on them.

Jamie is furious with Selris for allowing the Doctor and Zoe to enter the machine. He tries to get in.

The Doctor and Zoe struggle against the machine. They succeed and awake. Zoe notes that the device must convert mental power into energy. They see some bubbling tanks and realise that whereas the Gonds' mental energy was insufficient, their mental energy set the tanks into operation. The Doctor takes a sample and realises that it is a crystalline slurry for making life. Zoe discovers some pipes on the floor, similar to an astronaut's airlines. They notice something forming in the tanks. As it starts to climb out the Doctor and Zoe escape. As they do two Krotons, crystalline bipeds, plug themselves into the airlines and watch them on their scanners.

Outside Jamie is still trying to get in. He moves off in search of a crowbar.

The Krotons wander why the Doctor and Zoe are not following the same pattern as the other Gonds. They speculate as to whether the conditioning is failing.

The Doctor and Zoe make their way through an elaborate series of pipes and find a photo-electronic circuit that should open the door, however it has been disabled. The Doctor uses a piece of metal he has with him to complete the circuit manually. They door opens but they realise that they are on the cusp of where the deadly gas vaporises the Gonds.

The Krotons watch the reasoning of these Gonds in shock.

Zoe decides to risk it but they should drop down the side of the ramp and escape that way. They do so.

The Krotons decide to keep monitoring the Doctor and Zoe whilst also ordering the Gonds to bring them back. They speculate that they are not Gonds. They look in the Learning Hall and see Jamie attempting to enter. He is also not a Gond but another Gond, Selris, is watching on. They speculate the Gonds are working in alliance with a new race. They decide to take Jamie.

The door opens. Jamie, armed with the crowbar enters. He is immediately gripped by a Kroton. They test his mind. The machine starts and Jamie is paralysed. He tries to resist. The Krotons realise he has a primitive brain. They state that the machine will destroy him if he does. Jamie slumps to the ground...

Episode three Edit


Jamie undergoes Kroton mind probe.

One of the Krotons determines that Jamie may be able to provide information about the Doctor and Zoe and turns off the mind probe.

The Doctor decides to head back to the TARDIS. Zoe questions the safety of Jamie but the Doctor perseveres.

The Krotons question Jamie as to where he and his friends come from. They ask about the TARDIS and Jamie is forced to answer truthfully by the mind probe. They watch as the Doctor and Zoe enter the TARDIS. Jamie questions if they are heading off without him. The Krotons deliberate whether to destroy the TARDIS.

A group of Gonds, led by Security chief Eelek, approaches scientist Beta about how to attack the Krotons now that the Doctor and Zoe are presumed dead. Beta is reluctant, not out of fear as Eelek infers, but out of a lack of knowledge. The Krotons have taught the Gonds only what they want for them to know. Beta bemoans the inability of the Gonds to think for themselves and think they are just as unprepared and primitive as their ancestors. Eelek is impatient to act against the Krotons. He reveals there has been a vote amongst the counsel of the Gonds and that he has been announced the new leader.

They decide not to fire. They question Jamie about the operating principle and the transference interval of the TARDIS but Jamie cannot answer any of those questions. A Kroton is sent out to investigate.

Back in the Gond city Thara tends for Vana. Selris comes and tells of the fact that the Doctor, Zoe and Jamie have entered the machine and that he is going to call a counsel meeting to discuss what to do. Thara is resentful of Selris's apparent inaction and tells him of Eelek's power grab.

The remaining Kroton tells Jamie he is to be killed.

Thara tells Selris that the Gonds are fed up with talking and want war. Although Selris considers the Krotons enemies, he is more cautious about how to fight back than Eelek. He doubts Eelek's intentions and sees his ambition as more of a power grab.

Jamie questions what the Doctor and Zoe are needed for. The Kroton explains that high ability brains are needed for transferring power into the Dynatrope, the Kroton's name for their machine.

At the council meeting Beta openly argues with Eelek.

The Kroton tells Jamie that there is no way of destroying a Kroton. They can be rendered into molecular form but will always survive. Jamie is edging towards a weapon that he saw the other Kroton arm himself with.

Meanwhile the Doctor and Zoe have analysed the substance that they found in the tank and have discovered that it is Tellurium and they have also discovered that the smell in the air is Hydrogen Telluride. The Doctor wants to extract some of the sulphurous rock that is producing this gas. Zoe fears they are being watched.

They are, by a Kroton. Jamie watches on the screen and implores the Doctor and Zoe to get back in the TARDIS.

Zoe sees the Kroton and it orders them to return to the Dynatope.

Jamie attacks the other Kroton, it is disoriented.

Not being able to see in the light and after having lost contact with the other Kroton the Doctor and Zoe are able to escape. The other Kroton must ignore Jamie to provide directional data and instructs the Kroton to destroy the TARDIS. The Kroton fires a dispersion jet. Zoe is horrified when the mist clears and the TARDIS is gone, but soon after the Kroton returns to the Dynatrope, the TARDIS re-materialises. The Doctor turned on the HADS (Hostile Action Displacement System) before leaving, and they return to the Gond city.

Eelek and his men prepare to attack the Dynatrope directly. Selris enters and demands Eelek stop. Eelek ignores and leaves with his supporters. Selris has his own plan, which he shares with Beta, to attack the support pillars under the Dynatrope (accessible via the closed chamber in the Learning Hall). He hopes the attack will force the Krotons to emerge so they can be attacked directly.

The Kroton tells Jamie that, without high ability brain power, the Dynatrope will expire in three hours. Jamie escapes.

The Doctor and Zoe return to find Thara with the recovered Vana, preparing to leave the evacuated city. The Doctor is alarmed when Thara informs him of Selris's plan. He hurries off to the learning hall.

Selris is putting his plan into operation.

The Doctor stops off at Beta's lab to leave the sulphur and instructions. His alarm heightens when he realises Jamie may still be in the Dynatrope. The Doctor and Zoe rush off but Thara and Vana stay with Beta.

The Krotons notice that their Dynatrope is unbalancing.

Selris watches as cracks begin to form in the roof of the base unit of the Dynatrope. The Doctor enters the underchamber yelling for them to stop. Their efforts cause a massive rockfall. Some of the rubble falls on the Doctor...

Episode four Edit

The Doctor is shaken but otherwise unhurt, though several Gonds are injured, including Thara. The Krotons struggle to stabilize the Dynatrope, which is damaged slightly, while Jamie attempts to escape. Vana provides the Doctor with a small sample of Beta's sulphuric acid. The Doctor is horrified to learn that Jamie is indeed in the Dynatrope, though he escapes by his own ingenuity, to the Doctor and Zoe's delight. Jamie assists Beta with making sulphuric acid.


The Doctor and Zoe come up with a chemical plan.

While Eelek and Selris argue over leadership, a Kroton emerges from the Dynatrope, demanding the two high-brains (the Doctor and Zoe) be returned. Their minds are needed to produce energy to repair the drive mechanism and the Dynatrope is quickly running out of energy. The opportunistic Eelek realises that if they are captured, the Krotons will leave, though Selris suspects that the Krotons will destroy the Gonds regardless. Eelek and his men capture the Doctor and Zoe and force them into the Dynatrope. Selris takes a bottle of Beta's acid and leaps through the closing hatchway, passing it to the Doctor before being blasted out of existence by a Kroton.

The Doctor realises that if the Dynatrope's energy is exhausted, the resulting explosion will destroy the city as well. While he stalls them, Zoe dumps the acid into the crystal slurry tank, poisoning the Krotons. Meanwhile, Beta and Jamie reach the clifftop and pour the vat of acid over the Dynatrope, dissolving it. The Gonds rejoice at their freedom. Thara intends to fill his father's hereditary post as leader instead of the disgraced Eelek. Beta anticipates learning more from the Doctor. However, he finds that the travellers have left.

In the Wasteland, the TARDIS dematerialises.

Cast Edit

Crew Edit

References Edit

The Doctor Edit

  • The Doctor flatly states he isn't a doctor of medicine.

Science Edit


Story notes Edit

  • A preliminary outline for the story, then entitled The Trap, was submitted for season 2. It was rejected because the robots were deemed too similar to the Mechanoids, then set to feature in The Chase. Three years later, Holmes re-submitted the outline as The Space-Trap to a new, more receptive production team. The script — under the name The Space Trap — was actually commissioned for delivery in 1969, probably for the penultimate story of Season 6. However, because Holmes had completed the scripts early, the story went into production in late 1968 when a Dick Sharples story, Prison in Space, fell by the wayside.
  • All episodes of this serial exist in 35mm telerecording negative.
  • This story was repeated on BBC2 on consecutive evenings from Monday 9 to Thursday 12 November 1981 as part of the repeat season The Five Faces of Doctor Who as it was, at that time, the only complete four-part Patrick Troughton story available in the BBC Archives.
  • This is the first collaboration between writer Robert Holmes and script editor Terrance Dicks. It was only Dicks' second story in that capacity. In a neat bit of symmetry, Horror of Fang Rock was one of script editor Robert Holmes' last stories, written by Terrance Dicks.

Ratings Edit

  • Episode one - 9.0 million viewers
  • Episode two - 8.4 million viewers
  • Episode three - 7.5 million viewers
  • Episode four - 7.1 million viewers

Myths Edit

  • The Krotons were the winning entry in a Blue Peter 'design a monster' competition. (One of the winning entries in a Blue Peter 'design a monster competition, the 'Aqua-Man', resembled a cardboard box with legs and arms - similar to the Krotons' appearance.)

Filming locations Edit

Production errors Edit

If you'd like to talk about narrative problems with this story — like plot holes and things that seem to contradict other stories — please go to this episode's discontinuity discussion.
  • Beta is simultaneously in his lab and underneath the Learning Hall at the end of episode three.
  • Jamie collides with Zoe whilst climbing in episode one, and in the same scene her knickers are briefly visible.
  • The first shot is of a sliding door refusing to open.

Continuity Edit


Is this act of hypnotism a sign of psychic times to come?

Home video and audio releases Edit

DVD releases Edit

Digital releases Edit

  • Released in non-continental iTunes stores (Australia, Canada, UK and US) in standard definition as a collection of Doctor Who: The Classic Series.
  • On 4 November 2013, this story was released in standard definition in iTunes stores (Australia, Canada, France, Germany, UK and US) as part of the Doctor Who: The Classic Series collection Doctor Who: The Best of The Second Doctor, which additionally includes The Tomb of the Cybermen, The Ice Warriors, and The Seeds of Death.
  • This story was released in BBC Store, opened for UK residents on 5 November 2015.
  • The story is available for streaming in the US through Hulu Plus as Episodes 19-22 of Season 6 of ''Classic Doctor Who'' collection.
  • It is also available for streaming on Amazon Instant Video in the UK.

VHS releases Edit

  • This story was released on video as The Krotons in episodic format in 1991.

External links Edit

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