The Caves of Androzani (TV story)

The Caves of Androzani was the sixth and penultimate serial of season 21 of Doctor Who. It was the final regular appearance of Peter Davison as the Fifth Doctor and introduced Colin Baker as the Sixth Doctor in the closing moments of part four.

It was also Graeme Harper's first credited Doctor Who directorial job. Widely praised by fans, Caves was voted the single best televised Doctor Who story in a 2009 poll conducted by Doctor Who Magazine. (DWM 413)

As a regeneration story, it offered many unusual elements. Perhaps the most obvious was that it was written by Robert Holmes. Although the most prolific writer of the 1963 version of the programme, this was his only regeneration story. Caves was also the first regeneration story to allow for a brief scene with the incoming Doctor. Unlike any of his predecessors, the new Doctor was given the final words of the story — something that would happen in regeneration stories of the revived series. It was also the first time the Doctor willingly and explicitly underwent a regeneration solely to save a companion, which would later be repeated by the Ninth (TV: The Parting of the Ways) and Tenth Doctors. (TV: The End of Time) Furthermore, it was the first time since 1966's The Tenth Planet that the Doctor regenerated before the end of the then-current series, and the first since The Tenth Planet that occurred inside of the TARDIS. It was also the final time in the classic series that a Doctor would regenerate at the conclusion of their own story, rather than at the beginning of the new Doctor's introductory story. The practise of giving the departing Doctor a swansong was also revived by the modern series, following particularly in the template set by this and Logopolis where the entire story will be building up to the regeneration at the end of it.

From a behind-the-scenes perspective, Harper's direction was hailed by those involved with the production as highly innovative. Particularly noteworthy were Harper's more free use of camera movement than usual at the time and his direction from the studio floor. Harper's energetic and more personal directorial style sharply contrasted most who preceded him. Unlike Harper, most directors of the 1963 version of Doctor Who generally preferred to work in the booth and relay their messages to the actors and crew through the production assistant stationed on the floor. Peter Davison, in particular, found Harper's more direct style much to his liking. He lamented he had waited until his last story to receive this bolder style of direction, and that he would've stayed on the series longer if this directorial style was present during more of his tenure. (DCOM: The Caves of Androzani)

Another unique aspect of the production was its use of Shakespearian. Morgus, the principal villain of the piece, sometimes turned away from the characters and spoke his thoughts aloud, often appearing to break the fourth wall in the process by gazing into the camera. Though apparently the result of a mistaken impression about the script by actor John Normington, Harper kept the asides in, feeling they effectively ramped up the dramatic tension. (DCOM: The Caves of Androzani)

Synopsis
Arriving on the barren world of Androzani Minor, the Doctor and Peri find themselves embroiled in a long running war, fought between the ruthless General Chellak and the sinister Sharaz Jek. At the heart of the conflict is a substance called Spectrox - both valuable and deadly! The Doctor and Peri end up being poisoned by the material, which is killing them slowly and painfully, and there is no cure.

As the conflict heats up and the situation gets more desperate, and with death just hours away, how far must the Doctor go in order to save his friend's life?

Part one
The TARDIS lands on Androzani Minor, one of the twin planets in the Sirius star system. The Doctor and Peri find a spaceship has arrived, carrying a strange cargo. They decide to explore a set of tracks that lead into some nearby caves.

Deep in the caves, a soldier is killed by a Magma Beast. In another part of the caves, Peri catches her foot in an unknown, sticky and stringy substance. As the Doctor pulls her leg free, he gets some of the substance on his hand. Despite noticing that the substance has a strange stinging sensation to it, something Peri also complains about, he is unconcerned. As they keep exploring deeper into the cave system, Peri asks why the Doctor wears a stick of celery. He explains that it is a safety precaution. He is allergic to certain gases in the praxis range of the spectrum; in their presence, celery turns purple. They discover a hoard of weapons and hear several footsteps. Soldiers capture them and take them to their leader, General Chellak. As the two explain their innocence to Chellak and Major Salateen, there is a call from Trau Morgus, a business conglomerate leader on Androzani Major and CEO of the Sirius Conglomerate. Believing the two to be working for gunrunners Stotz and Krelper, he loses all interest in them and orders their deaths after seeing that Chellak's "gunrunners" are not his own men over holographic communication.

Deep in the caves, the masked madman Sharaz Jek has monitored the broadcast between Morgus and Chellak. He is delighted at Peri's beauty. Meanwhile, Chellak tries to reason with Morgus in an attempt to get him to relent on his decision to execute the prisoners, telling him that Peri and the Doctor have been fully cooperative and might give them more information if they are kept alive. But Morgus refuses, telling Chellak that there can be no negotiations with traitors.

In their cell, the Doctor and Peri await their deaths. The Doctor ponders what they have stepped into, noticing how Morgus lost all interest in them once he had had his look at them and his talk of fighting against android rebels. Peri comments that it hardly matters; the authorities seem hell bent on making the two of them scapegoats for whatever is going on. The Doctor apologises to Peri for getting them into this mess, telling her that curiosity has always seemed to be his downfall. Their conversation then turns to the strange fungus Peri stepped in; Peri complains that the rash on her leg is starting to develop into blisters, and the Doctor tells her that the same is happening to his hand, noticing that the substance must have some highly toxic properties. Peri grimly points out that whatever it was, it probably will not manage to kill them before the executioners can.

Meanwhile, in his lair, Sharaz Jek keeps the military base under close surveillance through hidden cameras. Looking at the Doctor and Peri in their cell and the soldiers preparing for the execution outside, he starts issuing orders to his androids.

In the cell, the Doctor's thoughts turn to the "spectrox," which both Chellak and Morgus were discussing during their interrogation of them. He wonders what it is and why Morgus named it the "most valuable substance in the universe". Peri asks him if he really does not know, and the Doctor answers that even his knowledge is not limitless. As they talk, a secret door in the back of the cell opens and a figure steps inside...

A business conversation between Morgus and the President of Androzani Major reveals the full picture of the Spectrox crisis. Spectrox is a powerful drug produced by bats in Androzani Minor's caves, which is the only known source of the drug. Spectrox is highly valued by the people of nearby Androzani Major for its ability to extend life and keep one's youthful looks somewhat intact.

The spectrox mines are controlled by Morgus, but the operation is threatened by the masked Sharaz Jek and his army of androids, causing public tension on Androzani Major over limited supplies. Morgus has funded a military operation by Androzani Major's government against Jek's androids. He has also secretly backed a gunrunning group to deliver weapons to Jek to profit from the war.

As Morgus and the President watch on a monitor, the Doctor and Peri are brought to the execution squad, dressed in red to hide the blood of their impending wounds. General Chellak asks if they have any last words; the Doctor tells him the whole thing is a mockery of justice, while Peri tells him just to get it over with. The soldiers step forward and take aim. On command, they blast bullets into the Doctor and Peri.

Part two
Chellak has the soldiers check their weapons. As the bodies are cut free of the execution posts, Morgus switches off the monitor. The President tells him that the people are not going to want to wait for their spectrox, especially considering most of them are unemployed. Morgus tells him that anyone without a valid work permit should be been sent to Eastern labour camps to reduce crime. The President points out to Morgus he has been closing plants in the West, which is why so many people are unemployed, and opening them again in the East. Meaning, if he accepts that suggestion, the same people will be working for Morgus again; this time without pay. Morgus innocently claims that he had never thought of that and the President sternly replies "No of course you hadn't" and leaves.

It turns out that the Doctor and Peri have been rescued by Sharaz Jek, who was watching them and had prepared android duplicates to take their place in the execution. They are taken to his base to become his companions in exile. Chellak and Salateen go to look at the bodies. When they turn out to be androids, Chellak realises his career is at risk. He decides to not let anyone know about it. Meanwhile, the Doctor asks Jek if he could show him and Peri the way to the surface, but Jek explains that he intends to make them stay with him and keep him company. He assures them, with a hint of threat in his voice, that he will take care of their every need. Meanwhile, Stotz is having trouble. Krelper is getting fed up with the lack of pay and their recent string of failures and wants to leave the gunrunning enterprise. But when Stotz threatens with killing him, Krelper relents and Stotz decides to let him live for the time being.

At Jek's base, the Doctor and Peri complain of rashes and cramps where they touched the sticky substance in the caves. Jek returns, and Peri asks him why he wants to keep them prisoners here. Jek answers that he is attracted to her beauty and that he likes the idea of having the Doctor as an intellectual sparring partner. He then tells the Doctor that he sees him as the most expendable person in this arrangement and he, therefore, expects him to be obedient towards him, warning him if he does not submit, then he will kill him. Peri, on the other hand, he intends to keep alive forever.

When Peri answers that eternal life is impossible, Jek explains that refined spectrox can extend someone's life, forever if need be, and he now owns all of it. "Until the army takes it away from you," comments the Doctor dryly, but Jek angrily retorts it will not happen. Thanks to his monitoring equipment, he knows the army's every move, and so far their fight against his androids have been slow and very costly in manpower for them; at the current rate it will take five years for the army to actually threaten his operations and by that time he expects the people of Androzani Major to have already risen up and forced the Presidium to agree to his terms: they can have all the spectrox they want once the head of Morgus lies at his feet.

Meanwhile, at Morgus' headquarters, Morgus is surprised to hear from Timmin that the copper mine has exploded. This takes care of overproduction and makes the price of copper rise. Morgus wants every employee to leave their place and stand in silence for a minute but then changes his mind and says half a minute.

Back at Jek's base, the Doctor meets Salateen. He has been a prisoner here, too. Jek captured him months ago and replaced him with an android that looks like him. The real Salateen resignedly realises Jek will probably kill him now he has them for company. When the Doctor suddenly gets another cramp and Peri remarks that she is having more as well, Salateen asks them if they touched a spectrox nest. Unsure, they describe the sticky substance and Salateen realises they did to which he breaks into a bitter laugh. He tells them that they are in the early stages of spectrox toxaemia, a very serious form of poisoning contracted from exposure to unrefined spectrox. He explains that cramps is the second stage (a rash being the first) and next their thoracic spinal nerves will slowly paralyse until they reach thermal death point, giving them only a matter of hours left to live. He also confirms there is an antitoxin, which was discovered by Professor Jackij: the milk of the queen bat. However, due to the mining activity, all the bats have fled to deeper levels of the caves, where there is no oxygen, making it next to impossible to acquire the milk. Worse still, Salateen tells them there is a carnivorous creature down there which has brutally killed and devoured several of Chellak's soldiers. He remarks that it probably lives in the deeper levels and comes up to the surface to hunt; adding that all anyone has ever found of it are "its table leavings".

Stotz contacts Jek and tells him his ship is in good shape and it wasn't his fault that the androids didn't show up. Before Jek leaves to meet with Stotz and the gunrunners, Peri asks why he wears a mask. Jek flies into a rage. Shaking with anger, he explains that he was once Morgus' business partner in the spectrox business. One day when he was working on Androzani Minor, a mud burst erupted, but Morgus had betrayed him by giving him faulty detection instruments, so he had no warning of the burst. Though Morgus left him to die, Jek managed to survive but was horribly scalded and disfigured. Ever since, he has tried to exact revenge on Morgus. Done with his explanation, he leaves them under the watch of his androids as he ventures out to meet up with Stotz.

In the lower levels of the caves, Jek meets up with Stotz and the gun-runners and announces that he will only hand over half of the promised spectrox, as they have failed to deliver the shipment. This greatly angers Stotz who demands all of the payment he was promised, but Jek refuses, telling him that it is their own fault they lost the weapon shipment. Fuming, Stotz threatens to stop doing business with Jek for good, but Jek says he fully well knows the value of spectrox and can very easily find himself another weapon supplier.

In Jek's HQ, the Doctor manages to get close to and reprogram the android guarding the entrance to the lair. Him, Peri, and Salateen then use this opportunity to make their escape. Meanwhile, Stotz pretends to relent to Jek's offer, but as Jek leaves to get the spectrox, he points out to his fellow gun runners that they can just follow Jek back to his base, walk past his androids, kill him and steal his spectrox. The Doctor, Peri and Salateen head into the lower levels of the caves to find the queen bat. Unfortunately, they encounter one of Jek's android guards who opens fire at them. One shot grazes the Doctor on the temple which knocks him unconscious. Salateen, using Peri as a human shield, fires back at the android and destroys it, he then forcibly drags her away from the Doctor despite her protests. The Doctor regains consciousness and discovers Peri has vanished. He goes to find her. Jek returns to his base but flies into a rage when he discovers that Peri has gone. The Doctor takes cover behind a rock as Stotz and the gun runners enter. The Magma Beast (the creature Salateen described) then appears and kills one of the gun runners. The other gun runners open fire on the beast. It ignores the bullets and approaches the rock where the Doctor is crouching.

Part three
The beast is distracted by the gun runners and turns on them again, killing another one of them. The Doctor escapes as the gun runners retreat. Meanwhile, Peri is taken by Salateen to General Chellak. They both explain to him what has happened, making Chellak realise the Salateen who has been at his side for months was an android, explaining how Jek was able to outwit the army so easily. Stotz and the gun runners encounter Jek who again offers half of the agreed amount of spectrox and this time they agree. The Doctor arrives back at Jek's base. He asks where Peri is but the Doctor tells him that he doesn't know. Jek does not believe him and gets the androids to torture him until he finally tells him that Peri is with Salateen, making Jek realise that Chellak will now know about the Salateen android. Stotz then arrives to collect the spectrox and wants to take the Doctor to Androzani Major, believing him to be a government spy. Jek allows them to but clearly isn't bothered. The Doctor is in the third stage of spectrox toxaemia and is feeling unwell, but Stotz doesn't care; the Doctor will live long enough to be questioned. In the army base, Peri also isn't feeling well, but General Chellak is also uninterested; she and the Doctor have been working with Jek which is a punishable offence. Chellak orders an assault on Jek's base. Salateen agrees to tell Morgus about the assault and to throw Jek off guard when he broadcasts a message.

Jek discovers the real Salateen is free to walk around the caves, leaving Peri unguarded. Meanwhile, Stotz chains the Doctor in the bridge of his spaceship and calls Morgus. As Stotz discusses the situation with Morgus, the businessman sees the Doctor still alive. He tells Stotz that Chellak faked the attack on Jek's base. Morgus is worried the President will see his double dealings. He tells Stotz to remain in orbit and Stotz, furious, leaves the Doctor on his own. When Stotz is gone, the Doctor tries to escape. He pulls himself free of the wall and uses the power core in the centre of the ship's bridge to sear the chains from his hands. He is still very weary from the Spectrox but programs the spaceship to land or "crash" on Androzani Minor.

Meanwhile, Morgus, fearing deception, invites the President into his office and opens his private lift so the President can leave. The President doesn't realise it's just an empty shaft. Morgus pushes the President into the lift and he falls to his death. Morgus then swiftly calls Timmin about the "terrible accident", telling her that he will assume command, and makes his own plans to travel to Androzani Minor to put the situation right himself. As Timmin is walking out, Morgus tells her to have the lift maintenance engineer shot.

Meanwhile, Jek kidnaps Peri and takes her back to his headquarters, where he finds the Doctor has gone. He is now insane and needs Peri's beauty to forget the trouble that Morgus has put him in. Peri tells him the army will attack soon, but Jek already knows that - he has changed the recognition code for the belt buckle. General Chellak and his men are in for a shock...

The Doctor is in the centre of the ship's bridge. Suddenly an extreme tiredness overtakes him, and his vision becomes distorted. However, he manages to shake it off and return to clarity as he hears shouting at the door. It is Stotz, who has been alerted by the loud, rumbling noise from the landing procedure. He demands the Doctor unlocks the door, but the Doctor refuses. Stotz shouts for something to cut the door open with and tries to coax the Doctor into opening the door willingly, but the Doctor rebuffs him, warning him that they'll be touching down shortly, or more likely crashing due to the fact that he's "a bit out of practice with manual landings" and advises Stotz to find something firm to hang onto. Stotz's men proceed to cut a hole in the door with a blowtorch, but the edges of the cutout is too hot for Stotz to reach the door controls, so instead, he points his weapon at the Doctor and threatens to shoot him. The Doctor notices that it is hardly a persuasive argument since he will die soon anyway unless he can cure his toxaemia. Stotz gives him to the count of three to surrender, but the Doctor is unmoved by this, and he tells Stotz that he owes it to Peri to find the antidote as he got her into danger in the first place. "So you see," shouts the Doctor defiantly as Stotz finishes his countdown, "I'm not gonna let you stop me now!"

Part four
The ship's rocket pods fire at the last moment, throwing Stotz's aim off and allowing the Doctor to violently land the ship on the surface of Androzani Minor. Still experiencing the effects of the Spectrox poisoning, the Doctor escapes from the spaceship. Krelper and another gun runner chase after him. Meanwhile, General Chellak plans the real assault on Jek's base, making him believe an attack lies elsewhere. As the assault force, guided by Salateen, heads towards the base, they come to a hold as they run into an android. Salateen assures them that there is nothing to fear, as the belt buckles will protect them, but as he moves towards the android to prove this, he is immediately gunned down. Panic erupts in the ranks as the soldiers realise that the signal is not working, and they frantically return fire. They eventually manage to disable all of Jek's androids, but at a very high cost of lives. Meanwhile, Krelper and his cohort are still chasing the Doctor. He approaches a cliff and falls from it. Rendered helpless for a moment, he is unable to get up as Krepler and the other gunrunner approach him, but just as they are about to kill him, a mudburst begins and they decide to leave the Doctor be and retreat to the safety of the ship. The Doctor gets to his feet and makes his way into the caves to save Peri.

Chellak and the few remaining soldiers have no choice but to push against the mudburst. Chellak sees Jek and chases him to his base. Once there, he struggles with Jek until he pulls his mask off. He is so horrified at Jek's scalded face that Jek is able to push him outside into the path of the mudburst. Jek goes to Peri. She screams at the sight of Jek's face and Jek himself lets out a cry of agony.

Morgus arrives on the planet. He finds Timmin has betrayed him and taken his dirty dealings to the government, which means he is now deposed from power and isolated from his wealth. Morgus declares that he is not beaten yet, and quickly works out a deal with Stotz. Krelper and his friend, however, have decided to cut their losses and want no part in it. Stotz pretends to accept this only to shoot and kill them as soon as their guard is down. Morgus and Stotz continue on ahead, plotting to secure Jek's private stash of spectrox so they may disappear quietly to another planet.

The Doctor arrives at Jek's base, struggling to hold off the effects of the Spectrox poisoning, and the regeneration that would rid him of the infection. When the Doctor explains that he can hold his breath much longer than a human and therefore has a better chance to survive in the lower parts of the caves, Jek provides him with an oxygen tank and directions, so he can find the queen bat and milk it. The Doctor then departs to get the milk. While wandering through the caves he comes across the Magma Beast lying dead. He briefly squats down to inspect the creature and remarks "It's not your lucky day either" and carries on.

Morgus and Stotz make their way to Jek's base, lured by extractor fans that Jek is using to keep the base temperature cool for Peri. Morgus orders Jek to give him the Spectrox. Jek sees Morgus and, consumed by rage, forgets all about Peri and everything else. He pulls off his mask, showing Morgus his scalded face. As Morgus looks at Jek in shock, Jek throttles him. Stotz opens fire on Jek, but the Salateen android returns and kills him. With his last ounce of life, Jek pushes Morgus' head into his extractor fans. Morgus dies in seconds and the extractor fans short circuit and burst into flames. Jek dies in the arms of the Salateen android, giving it his last orders to hold him. The Doctor arrives just after the battle and escapes, but the Salateen android stays where it is as the fire destroys Jek's base.

The Doctor takes the unconscious Peri back to the surface and the TARDIS, but a mud burst is on its way. While he unlocks the TARDIS, the Doctor spills some the bat's milk in the sand. He manages to open the door, get himself and Peri inside the TARDIS and dematerialise as the planet's surface explodes in boiling mud.

Inside the TARDIS, the Doctor feeds Peri all of the remaining bat's milk, then collapses on the floor of the TARDIS, now so close to death that he is starting to doubt that regeneration is possible, saying aloud "Is this death?". Peri recovers to find the Doctor lying in pain on the floor. The Doctor quickly explains he cured her with the bat's milk, but he only had enough for her. He tells Peri that there's nothing she can do, that he will be going soon, and it's time to say goodbye. Peri encourages him not to give up and pleads that he can't leave her now. He then says that he "might regenerate", but he doesn't know for certain that he will be able to, because the process "feels different this time".

A bright glow surrounds the Doctor as his image distorts; he begins hallucinating his previous companions urging him to live, telling him the universe still needs him. He is particularly affected by the vision of someone who died, and his final word is, "Adric?" A vision of appears, laughing at the Doctor and telling him to die. The visions of his companions begin to swirl, all their voices overlapping together and drowning out the taunts of his foe. The glow grows brighter and covers the Doctor. As the visions subside all at once, it fades to reveal the Doctor's new incarnation, a man with a sharp gaze and curly blond hair atop his head. Peri moves toward the regenerated Doctor and addresses him by name. The Doctor, now sitting up and fully alert, challenges his now-detoxified assistant with the words, "You were expecting someone else?" Speechless, she trips up, "I, I, I..."

He ironically scolds her, "That's three I's in one breath. Makes you sound a rather egotistical young lady." Peri asks, "What's happened?" He grandly declares, "Change, my dear, and it seems not a moment too soon," staring forward with a proud grin and a glint in his eye.

Cast

 * The Doctor - Peter Davison
 * Peri Brown - Nicola Bryant
 * Sharaz Jek - Christopher Gable
 * Morgus - John Normington
 * Salateen - Robert Glenister
 * Stotz - Maurice Roëves
 * Chellak - Martin Cochrane
 * Krelper - Roy Holder
 * Timmin - Barbara Kinghorn
 * President - David Neal
 * Soldier - Ian Staples
 * - Anthony Ainley
 * Adric - Matthew Waterhouse
 * Nyssa - Sarah Sutton
 * Tegan Jovanka - Janet Fielding
 * Turlough - Mark Strickson
 * Voice of Kamelion - Gerald Flood
 * The Doctor - Colin Baker

Uncredited cast

 * Salateen android - Robert Glenister
 * Gun-runners - Les Conrad, Robert Smythe, Gerry O'Brien (DWM 279)

Crew

 * Assistant Floor Manager - Sue Hedden
 * Camera Supervisor - Alec Wheal
 * Costumes - Andrew Rose
 * Design Effects - John Peyre
 * Designer - John Hurst
 * Film Cameraman - John Walker
 * Film Editor - Roger Guertin
 * Film Sound - Malcolm Campbell
 * Incidental Music - Roger Limb
 * Make-Up - John Nethercot, Shirley Stallard
 * Producer - John Nathan-Turner
 * Production Assistant - Juley Harding
 * Production Associate - June Collins
 * Production Managers - Elizabeth Trubridge, Corinne Hollingworth
 * Script Editor - Eric Saward
 * Special Sounds - Dick Mills
 * Studio Lighting - Don Babbage
 * Studio Sound - Scott Talbott
 * Technical Co-ordinator - Alan Arbuthnott
 * Theme Arrangement - Peter Howell
 * Title Music - Ron Grainer
 * Videotape Editor - Steve Newnham
 * Video Effects - Dave Chapman
 * Vision Mixer - Dinah Long
 * Visual Effects - Jim Francis, Stuart Brisdon

Planets

 * Androzani Major and Androzani Minor are "twin planets."
 * Androzani Major and Androzani Minor are located in the star system of Sirius.

Individuals

 * Morgus is or was, rather, before being deposed by Timmin, "the richest man in the Five Planets," chairman of the Sirius Conglomerate and a descendant of the first colonists.
 * The Doctor claims to be able to store oxygen for several minutes.
 * The Doctor confesses to Peri he tried to keep a diary, but he never finds the time to update it.
 * Salateen explains that the cure for Spectrox toxaemia was discovered by Professor Jackij.
 * Boze is one of the people killed by the Magma Beast. Rones was killed in a gas attack.
 * The Doctor's last word before regenerating is "Adric?"

Technology

 * Peri mentions a reticular vector gauge.
 * In the smugglers' cave, the Doctor and Peri find gas carbines, bombs and poison volatisers.
 * Analysing traces of fused silica on the ground of Androzani Minor, the Doctor deduces a small spaceship had recently landed.
 * The Doctor also demonstrates tracking skills by studying monoskid tracks and deducing it had departed with a heavy load and returned unloaded.
 * Sharaz Jek's androids come in various models; some of them are simple soldiers that can follow orders but are programmed to shoot humans on sight. More specialist models include the duplicates of the Doctor, Peri and Salateen.
 * Belt plates are used by Jek and the gun runners to protect themselves from the androids. Salateen gets hold of one and they're mass-produced by the army. Jek changes the frequency code before the army attacks so the androids attack them.

Substances

 * The Doctor wears a stick of celery because he is allergic to certain gases in the praxis range of the spectrum, the presence of which causes the celery to turn purple.
 * When refined, Spectrox can slow the ageing process of the taker. When unrefined, it causes Spectrox toxaemia on contact.

Illnesses

 * Spectrox toxaemia causes a rash, cramp, spasms, slow paralysis of the thoracic spinal nerve and finally thermal death. Milk from a Queen Bat is the only known cure besides regeneration (though the latter is unique to Time Lords).

Story notes

 * Despite the title, the Doctor notes that the caves are in fact blowholes.
 * The maps of the caves shown on screen bear an superficial resemblance to the video game Dig Dug.
 * This story had the working title of Chain Reaction.
 * The regeneration sequence features specially recorded cameos by Matthew Waterhouse, Janet Fielding, Sarah Sutton, Mark Strickson, Gerald Flood and Anthony Ainley. Because Waterhouse & Sutton had left the show in previous seasons, special contracts had to be written for their cameos. Furthermore, Nyssa's appearance in the episode required the producers to pay her creator, Johnny Byrne, royalty fees.
 * The closing credits for Part 4 were altered specially for the incoming Doctor. As the credits started rolling, it fades directly from the close up of Colin Baker having just delivered his line, to a multi-coloured image of him with a similar expression superimposed over the regular credit sequence before his credit as the Doctor appears, followed by Davison's credit. The face moves back along the screen and fades out as soon as Davison's face in the regular credit sequence disappears and it then continues as normal.
 * This was the second instance where Peter Davison is credited second in a regeneration story. The first being the ending of TV: Logopolis, which was Tom Baker's final appearance in the lead role.
 * This is the first time an explanation has been given for the Doctor wearing celery on his lapel.
 * This story marks the first occasion since 1980's TV: The Keeper of Traken or 1977's TV: Horror of Fang Rock if Nyssa's pre-companion role in Season 18 is discounted that the Doctor has spent a complete adventure with only a single incumbent companion, and the first time since 1977's TV: The Invisible Enemy or, again, Horror of Fang Rock if K9 Mark I's pre-companion role is discounted, that the Doctor has travelled without any non-human companions.
 * In DWM 400, The Caves of Androzani was voted the readers' favourite televised story. Conversely, The Twin Dilemma, the very next serial, bottomed out at #200 as the least favourite, effectively bookending the charts.
 * The only characters who do not die during this story are Peri and Timmin, who are also the only female characters: counting the Doctor's regeneration as the death of his fifth incarnation, every male character dies. The Salateen android is not destroyed on-screen, but it is not definitely shown as surviving the story's events and it's debatable whether an android would count as being "alive" in the first place.
 * This story was rife with on-screen mishaps that ended up causing minor injuries to Peter Davison; Davison himself would later jokingly claim that the staff were actually attempting to kill him. Among these accidents are two notable instances:
 * During a scene in which Sharaz Jek backhands the Doctor, the mask Christopher Gable was wearing impaired his vision enough to make him legitimately strike Davison by mistake.
 * As the Doctor carries Peri back into the TARDIS at the end of the story, he flinches at a nearby mud burst. This is because the explosion was prematurely triggered by the technicians, shooting sand into Davison's eyes and forcing him to recoil in pain.
 * The effect used for the Doctor's distorted vision near the end of Part 3 is the same effect used for his regeneration at the end of the serial. It was also used in Resurrection of the Daleks for the destruction of the space station.
 * This story is notably one of few where the eventual outcome negates the importance of the plot. The Doctor's role provided no historical accomplishments and instead caused an inadvertent massacre, a gigantic power collapse, and even his own "death", all of which could've been prevented had the Doctor never been involved or even went to Androzani Minor, for that matter.
 * This story was chosen by fans to represent the Peter Davison era by fans to be rebroadcast for Doctor Who @40.
 * This is the first regeneration story to include the new Doctor's first words, rather than waiting until their first full story. This practice would become the standard in the revived series.
 * Graeme Harper recalls in the DVD commentary that he and Christopher Gable had worked together on numerous occasions in the past but never with Harper as a director. Over the years they knew each other, Gable affectionately called Harper 'Twinkle' and had even embarrassed him by calling him it at a public event. Harper made Gable promise not to call him the name on the set of this story for fear of what it might do to his reputation. Peter Davison admitted he would have found it very hard to take Harper seriously if he had heard Gable use the name.
 * A concrete date was finally made in Diamond Dogs, which takes place in the 51st century and refers to Sharaz Jek as being an active criminal.
 * Peter Davison has since stated that he felt that his performance during the regeneration sequence was overshadowed at the time by the obvious visibility of Nicola Bryant's cleavage during the shot. (DOC: The Ultimate Guide)
 * The story was the last of three consecutive serials, along with Resurrection of the Daleks and Planet of Fire, that saw the departure of one of the season's regular cast members. In this serial, Peter Davison departs as the Fifth Doctor.
 * Christopher Gable was originally offered the role of Salateen. Graeme Harper wanted him for Jek but didn't think he would accept, as he'd be hidden behind a mask for the whole story, but Gable wanted the challenge and the larger role.
 * Peter Davison named this as his favourite serial (claiming that if he'd gotten more stories of this quality earlier in his run he would have wanted to stay on longer), Nicola Bryant named it as her favourite from her first series and John Nathan-Turner named it as one of the highlights of his tenure.
 * Eric Saward wrote two scenes - the Doctor's explanation as to why he wears celery and the Sixth Doctor's scene.
 * Recording was interrupted by a strike, which caused a serious delay in the filming of the serial. As a result, two sequences had to be cut. The first scene would have featured the Doctor and Peri at the opening of the story in the TARDIS. The Doctor was to explain to Peri the reason for their visit to Androzani Minor. Apparently, as a boy, the Doctor had started a "blown glass bottle collection", which was made from the sand of different planets. He had lost his Androzani bottle and decided to return there to retrieve some more sand. It was in this scene Peri was to say "You're such a pain, Doctor." However, when the final cut of the serial was made, it had been discovered that certain lines of dialogue (like the Doctor professing that "I am not a pain" and Peri's comments about needing sand to "make some glass") alluded to the cut sequence. To rectify this, Peter Davison and Nicola Bryant voiced over part of their conversation while the TARDIS materialises from outer space to the planet. The second scene to be cut would have featured the Doctor battling with the magma beast in episode four.
 * Peter Davison and Robert Glenister previously co-starred in the sitcom Sink or Swim.
 * Robert Glenister is best known for his role in Hustle. Colin Baker guest-starred in the episode "Tiger Troubles".
 * The scene where Morgus faces the camera directly and speaks out his inner thoughts came about from John Normington misunderstanding the stage directions he was given. However, everyone liked the theatrical feel of it and that take was left in the episode.
 * Tim Curry, David Bowie and Mick Jagger were offered the role of Sharaz Jek. Also considered were Derek Jacobi and John Hurt. Of these five, Bowie is the only one whose refusal we actually know the reason for: the scheduled taping dates conflicted with his Serious Moonlight tour. Patrick Allen, Nicholas Ball, Steven Berkoff, Brian Cox, Michael Gambon, Julian Glover, Martin Jarvis, Michael Jayston and Oliver Tobias were also considered.
 * Steven Berkoff, Michael Gambon and Julian Glover were considered for the role of General Chellak.
 * Joss Ackland, Patrick Allen, George Baker, Ian Bannen, Julian Glover, Ian Holm, Martin Jarvis and Michael Jayston were considered for the role of Morgus.
 * Nicholas Ball, Ralph Bates, Christopher Cazenove, Tom Chadbon, Nicholas Clay, Brian Cox and Donald Sumpter were considered for the role of Salateen.
 * Patrick Allen, Alun Armstrong, Nicholas Ball, Steven Berkoff, Warren Clarke, Kenneth Cope and Michel Elphick were considered for the role of Stoltz.
 * Graeme Harper hoped to bring Michael Craze back to play Krelper, only to be vetoed by John Nathan-Turner.
 * In the original script, the Doctor did not regenerate after succumbing to spectrox toxaemia, but simply because of the damage his body sustained in combating Stotz and his gunrunners.
 * Eric Saward thought it was an above average script that was elevated by Graeme Harper's direction.
 * The Praxis range reference to the allergic gasses came from Eric Saward's Praxis 35 typewriter.
 * Eric Saward came up with the magma beast, which displeased John Nathan-Turner.

Influences

 * Frank Herbert's Dune: people fighting a war over a drug that extends life; the unstable "tripod of power" between the rulers of Androzani; the "mud bursts" and Androzani Minor's generally arid climate.
 * Gaston Leroux's Le Fantôme de l'Opéra]: a mentally unbalanced but brilliant recluse wears a mask to conceal his facial disfigurement; develops an obsessive fascination with an attractive young woman and eventually abducts her.
 * The New Testament: The Doctor uses up his supply of life-giving fluid to save someone else, and his fresh corpse is attended by a loyal female disciple. He is soon restored to life by the intervention of a higher power, and rises up in perfect health. Oddly enough, the name Peter Davison has connections to the New Testament story: Davison means Son of David, a title often applied to Jesus Christ, and Peter was one of Jesus' primary travelling companions.
 * I, Claudius: the Doctor seeing his former companions as he regenerates is similar to Claudius seeing the people in his life before he dies.
 * The Beatles: the sound effect used during the regeneration was inspired by "A Day in the Life".

Ratings

 * Part one - 6.9 million viewers
 * Part two - 6.6 million viewers
 * Part three - 7.8 million viewers
 * Part four - 7.8 million viewers

Filming locations

 * Masters Pit, Hansons Aggregates, Stokeford Heath, Dorset
 * BBC Television Centre (TC6), Shepherd's Bush, London

Production errors

 * Nicola Bryant, or her stunt double, visibly pushes herself off the ledge in order to fall from the ledge in part one. She then bounces, obviously having landed on a safety cushion of some kind.
 * In part one, Nicola Bryant accidentally lets slip her natural English accent, particularly when she says the word 'glass'.
 * The electronic device that Morgus uses in his office during his first scene in part one is obviously a TV/teletext remote control, with John Normington's thumb conveniently placed to hide the manufacturer's logo.
 * When Stotz cuts through the door of his ship, the polystyrene is visible on the fake door.
 * Androzani Minor is supposed to be barren, deserted and uninhabited. Yet in part four, shots of the Doctor being chased by the gunrunners show a house and tree-lined hills.
 * During the end of the scene in part four where Stotz shoots Krelper, a tiny sliver of the studio lights and the actual studio floor can be seen.
 * The background changes position as the TARDIS dematerialises.
 * The skin around Jek's right eye is shown to be normal colour throughout the serial but when he finally removes his mask in part four, his whole face is grey.

Continuity

 * Speaking about the mud in the Androzanian landscape, Peri says it's "a change from lava". (TV: Planet of Fire)
 * Peri and the newly-regenerated Sixth Doctor quickly become immersed in another adventure. (TV: The Twin Dilemma)
 * AUDIO: Winter takes place during the Doctor's regeneration, which reveals that the Master's appearance as the Doctor dies is the result of him using his and the Doctor's old telepathic link to Kamelion to try and 'block' the Doctor's regeneration, requiring indirect support from the Fifth Doctor's other companions to keep him alive.
 * The Doctor survives in the vacuums of Androzani Minor's caverns through use of an oxygen cylinder, and later his respiratory bypass system. (TV: Pyramids of Mars)
 * Following this story, the Sixth Doctor goes through a brief period where he subconsciously blames Peri for his previous self's death. He tries to distance himself from her while telling himself that he is working towards a greater good, until he finally realises this in PROSE: Burning Heart.
 * In PROSE: Timewyrm: Revelation, it is revealed that after the Fifth Doctor dies, he becomes the mental personification of the Doctor's conscience, but is buried by the Seventh Doctor following his regeneration.
 * An alternative version of the Doctor never visited Androzani Minor. (PROSE: So Vile a Sin)
 * In PROSE: Matrix, an alternative timeline is referenced where the influence of the Dark Matrix, wielded by the Valeyard, the Doctor's dark future self, provokes the Fifth Doctor to take the bat's milk himself while leaving Peri to die, turning the Fifth Doctor into a wraith loyal to the Valeyard until this is undone by the Seventh Doctor.
 * Trees, technology, and soldiers from Androzani Major all play a major factor in a Christmas adventure for the Eleventh Doctor. (TV: The Doctor, the Widow and the Wardrobe)
 * The Doctor was stated to have died on Androzani Minor after the Great Intelligence had entered the Doctor's time stream. He was, presumably, saved by a version of Clara Oswald. (TV: The Name of the Doctor)
 * Due to her infection with spectrox toxaemia, Peri was rendered infertile. (AUDIO: The Widow's Assassin)

DVD releases
Released as Doctor Who: The Caves of Androzani, this release was the third of 2001 and the second to feature the Fifth Doctor. It features a different image of Peter Davison on the cover to later releases (in common with The Robots of Death, Vengeance on Varos and Remembrance of the Daleks, the first stories released for the Fourth, Sixth and Seventh Doctors).

Released:
 * Region 2 - 18 June 2001
 * PAL - BBC DVD BBCDVD1042


 * Region 4 - 7 January 2002
 * Region 1 - 2 April 2002
 * NTSC - Warner Video E1606

Contents:
 * Audio Commentary by actors Peter Davison (the Doctor), Nicola Bryant (Peri) and director Graeme Harper
 * Chain Reaction - Making of
 * Directing Who: Then and Now - with Graeme Harper
 * Behind the scenes - The Regeneration - Footage of final studio session, with commentary.
 * Behind the scenes - Creating Sharaz Jek - Interview with Christopher Gable.
 * BBC News - Report of Peter Davison's departure (28 July 1983).
 * South East at Six News - Peter Davison and John Nathan-Turner talk about the future of the series.
 * PDF materials - Radio Times Listings
 * Extended Scene
 * Music-only Option
 * Trailer
 * Photo Gallery
 * Production Subtitles

Rear Credits:
 * Starring Peter Davison
 * By Robert Holmes
 * Produced by John Nathan-Turner
 * Directed by Graeme Harper
 * Incidental Music by Roger Limb

Notes:
 * Editing for the DVD release was completed by the Doctor Who Restoration Team.

Special Edition release
This story was released as Doctor Who: The Caves of Androzani: Special Edition.

Released: Special Features:
 * UK 4 October 2011 Region 2
 * Australia 2 December 2010 Region 4
 * US 14 February 2012 Region 1
 * Chain Reaction - The making of The Caves of Androzani
 * Directing Who, Now and Then - Graeme Harper
 * Russell Harty - chat show excerpt with Peter Davison and Colin Baker
 * New Photo Gallery
 * All previously released bonus features

Notes:
 * It is only available in Australia as part of the Revisitations 1 box set, out in Region 2 on 4 October 2010. It was released with special editions of The Talons of Weng-Chiang and Doctor Who. It is additionally available in the UK, rather bizarrely, as part of the HMV-exclusive An Introduction to the Fifth Doctor box set, along with Castrovalva and Earthshock.