Series 16: The Armageddon Factor

In their search for the final segment of the Key to Time, the Doctor and Romana arrive on the planet Atrios, which has endured a recent bombing by their neighbouring planet Zeos, with whom they are at war. The Marshal of Atrios is about to launch a counterstrike on Zeos, but the Doctor finds that Zeos is deserted save for the giant computer Mentalis, which is controlling the war. He also discovers that the true opponent is a third planet called the Planet of Evil, ruled by "the Shadow". The Shadow, an agent of the Black Guardian, has Princess Astra of Atrios captive, threatening to torture her if she doesn't give him the location of the final segment of the Key to Time (which she doesn't know).

After disabling Mentalis, with the assistance of Romana and K-9, the Doctor creates a substitute sixth segment out of chronodyne, which gives the Key enough power to create a time loop in which to trap the Marshal's ship (armed with missiles for the final strike) as well as the Mentalis control room (engaged in an automatic self-destruct sequence). On the Planet of Evil, the Doctor encounters an old Academy mate, a fellow Time Lord named Drax, who has been employed under duress by the Shadow but agrees to help the Doctor.

With K-9 and Astra now under his control, the Shadow wants the Key for himself, and forces the Doctor to retrieve it for him. The Doctor leads the Mute to his TARDIS and opens the door, but is suddenly shrunk to tiny size by Drax, using the dimensional stabilizer from his own (in-need-of-repair) TARDIS. (Originally, as implied by the Doctor's reaction, Drax was supposed to use the shrinking beam on the Mute, but deliberately misaims and shrinks the Doctor instead. Episode 5 ends on this scene, and it's only at the beginning of Episode 6 that Drax shrinks himself as well, having misinterpreted the Doctor's plan.)

The Mute returns to the Shadow with the Key, but the Doctor realises why the Shadow has requested it: Astra is the final segment, and is transformed in front of everyone. Using their diminished size, the Doctor and Drax smuggle themselves into the Shadow's lair inside of the now-restored K-9. Drax again uses the stabilizer, this time to return them to their normal size. The Doctor snatches the partially assembled Key and the final segment, and disappears with Romana and K9 in the TARDIS, assembling the Key after dealing with the Mentalis self-destruct (with the help of Drax) as well as the Marshal's missiles (using the TARDIS to deflect them onto the Planet of Evil).

The White Guardian appears to congratulate the Doctor on finding and assembling the Key to Time, and requests that it be sent to him. However, the Doctor, realising that it is actually the Black Guardian in disguise, orders the Key to re-disperse. Enraged, the Black Guardian, now reverted to his true form, threatens him with death. In an attempt to shake him off, the Doctor fits a randomiser into the TARDIS console, sending it to an unknown location in time and space, and leaving the Doctor and the Guardian with no idea of where they are headed.

Cast
Doctor Tom Baker (Fourth Doctor)
Companions John Leeson (K-9 Mk. II)
Mary Tamm (Romana I)
Guest stars
Lalla Ward — Princess Astra
John Woodvine — The Marshal
Davyd Harries — Shapp
Ian Saynor — Merak
Ian Liston — Hero
Susan Skipper — Heroine
William Squire — The Shadow
Barry Jackson — Drax
Valentine Dyall — The Guardian
John Cannon, Harry Fielder — Guards
Iain Armstrong — Technician

Production
Writer Bob Baker
Dave Martin
Director Michael Hayes
Script editor Anthony Read
Douglas Adams (uncredited)
Producer Graham Williams
David Maloney (uncredited)
Executive producer(s) None
Production code 5F
Series Season 16
Length 6 episodes, 25 minutes each
Originally broadcast January 20–February 24, 1979

source: wikipedia

Series 16: The Power of Kroll

In the far future on one of the moons of Delta Magna, Delta Three, sits a vast methane and protein collection and manufacturing refinery. The staff of four – the bullying leader Thawn, and his technical support Fenner, Harg, and Dugeen – are in charge of the operation. A green-skinned humanoid native called Mensch, one of the Delta Magnans, serves them. These servile people were once the inhabitants of the main planet but were moved to Delta Three when the Earth Empire identified Delta Magna as commercially valuable; sadly for the green-skinned natives, known as Swampies, this is now also the case on Delta Three. Thawn becomes concerned about the possibility of insurrection when he learns both that the environmentalist group Sons of Earth has taken an interest in Delta Three and that the gun-runner Rohm Dutt is rumoured to be journeying there. Thawn and Fenner head outside the refinery to see if he has arrived, suspecting a mysterious spacecraft which has touched down nearby is Rohm Dutt’s.

The Fourth Doctor and Romana have also arrived on Delta Three, searching for the penultimate segment of The Key to Time. However, the Tracer they are using to locate the segment is giving some very strange readings that makes their quarry difficult to pinpoint. They are ambushed by Swampies and Romana ends up getting taken away with Rohm Dutt and a Swampie patrol, while the Doctor is found by Fenner and Thawn and returned with them to the refinery. There he displays a bewildering familiarity with the methane catalyzing process, with the refined protein then shot into space for delivery to Delta Magna. The Doctor is also intrigued by the position of Mensch, whom the refinery workers do not even regard as a properly sentient being. The Doctor slips away to try and find Romana, but she has meanwhile got herself into a degree of trouble. The Swampies have tied her to a rock and are prepared to sacrifice her to Kroll, a giant squid creature that lives beneath the swamps and which they worship as a god. When it appears from the waters, Kroll is a vast squid – or rather a Swampie dressed as one. The Doctor unmasks the fake monster and rescues Romana.

Back at the refinery, Dugeen has detected a vast living creature some two miles wide inside the swamp. The Doctor and Romana have meanwhile found reference to the real Kroll in a Swampie testament, which says the enormous creature ate a previous Swampie High Priest and has made three appearances with a fourth due soon.

Rohm Dutt has supplied the Swampies with weapons but when they are used against Thawn, who is searching the swamps for the Doctor, they are found to be defective and explode whenever fired, resulting in the death of one of the Swampies. Seconds later, a huge tentacle erupts from the water and seizes Mensch, dragging him to his death. In the confusion, Rohm-Dutt calls out to Thawn; his cries go unnoticed however, as everyone's eyes are drawn to the vast squid-like creature that emerges from the swamp, towering above the horizon (as shown in the picture above). Kroll is very real, very large and very hungry. Ranquin attempts to mollify it with prayer, and Kroll disappears beneath the surface of the swamp. Despite Ranquin's belief that Kroll has spared his believers, the monster has simply failed to notice the Swampies, and it is soon drawn to the refinery. One of its tentacles enters a pipeline and soon smashes its way inside, dragging crewmember Harg to his death.

The gun-runner is taken as a prisoner back to the Swampie camp, where the Doctor and Romana arrive and introduce themselves to the tribe and its leader Ranquin. The elder decrees all three "dry-foots" will die by the seventh ritual of Kroll: a cumbersome and painful affair involving the stretching of the victims on creepers and wood that will eventually snap their backs. In fear, Rohm Dutt admits Thawn paid him to sell the faulty weapons to the Swampies as a means to discredit the environmentalist Sons of Earth movement. All three are secured and their punishment begins as a violent storm starts on Delta Three. The Doctor rescues himself, Romana, and Rohm Dutt with "high pitched vocal vibrations", which shatter a window above, allowing the rain to pour in on the vines. This relaxes them enough for the trio to escape, pursued by the Ranquin and his tribe.

The three refinery crew now decide to redirect the orbit shot against Kroll. They note the creature is now on the move towards the Swampie settlement. When it reaches there its first victim is Rohm Dutt. The Doctor deduces that the creature hunts by vibration, and uses this knowledge to keep himself and Romana safe from the tentacles. The enormous Kroll now rises to the surface of the swamp and destroys the Swampie settlement, killing many Swampies before submerging again.

The Doctor and Romana now sneak back into the refinery and are horrified that Thawn calculates the missile strike will destroy the creature and the Swampies. Dugeen is equally appalled, and when he tries to stop the missiles being fired, Thawn kills him. The Doctor, however, is more successful and manages to disconnect the firing mechanism in the rocket silo. Thawn investigates and finds the two culprits, more convinced than ever that they are Sons of Earth spies too. The tables are turned, however, when the Swampies attack the breached refinery and kill Thawn. Ranquin, who has led the assault, believes the deaths of the “dry foots” will help atone to Kroll, but the creature is now above the swamp again and hurling itself against the bulk of the refinery.

While Ranquin fruitlessly prays to Kroll in an effort to stop the attack, the Doctor orders that all the refinery's equipment be activated, in order to try and confuse Kroll. It has the desired effect, and the attack stops. Ranquin refuses to let his faith in Kroll be shaken however, and upon finding one of Kroll's tentacles, begs his god to destroy the "dry foots." Instead, Kroll simply grabs hold of Ranquin and drags him away to his doom. The remaining Swampies realize the creature is beyond appeasement. It is not, however, beyond science. The Doctor has worked out that Kroll has been magnified to giant proportions by a segment of the Key to Time, disguised as a Swampie relic which the squid creature swallowed along with a previous High Priest. He uses the Tracer to eliminate the giant Kroll and retrieve the fifth segment of the Key.

The Doctor finally saves the refinery from destruction by aborting the automatically scheduled orbit shot, which would have resulted in an explosion, and then tells Fenner, the only survivor of the refinery crew, to use his time wisely until a rescue mission arrives from Delta Magna, and to try to understand the Swampie culture. The Doctor and Romana head back for the TARDIS with another segment of the Key in their possession.

Cast
Doctor Tom Baker (Fourth Doctor)
Companion Mary Tamm (Romana I)
Guest stars
Neil McCarthy — Thawn
Philip Madoc — Fenner
John Leeson — Dugeen
Grahame Mallard — Harg
Glyn Owen — Rohm-Dutt
John Abineri — Ranquin
Carl Rigg — Varlik
Frank Jarvis — Skart
Terry Walsh — Mensch

Production
Writer Robert Holmes
Director Norman Stewart
Script editor Anthony Read
Producer Graham Williams
John Nathan-Turner (uncredited)
Executive producer(s) None
Production code 5E
Series Season 16
Length 4 episodes, 25 minutes each
Originally broadcast December 23, 1978–January 13, 1979

source: wikipedia

Series 16: The Androids of Tara

The society of the planet Tara is a mix of the feudal and the futuristic, with a rigid social monarchical hierarchy developed alongside a skill in advanced electronics and android making, which is an ability endowed on the lesser orders. Centuries earlier a plague wiped out nine tenths of the population and the peasants, abandoned by the nobles at that time, began building androids to deal with labour shortages. The planet is now troubled by a struggle for the crown and the power on Tara. The rightful heir, Prince Reynart, is facing a challenge to his rule and coronation from his cousin, Count Grendel of Gracht, a suave but deadly villain who has kidnapped Reynart’s sweetheart, the Princess Strella, and is holding her captive to persuade Reynart not to take the throne.

The Fourth Doctor and Romana arrive on Tara in search of the fourth segment of The Key to Time and, for once, the quest is simple. While the Doctor goes fishing, Romana identifies and transforms the fourth segment alone – it was disguised as a segment of a Grachtian statue – though her luck does not last. She is attacked by a native Taran bear and only saved by Count Grendel, who confiscates the segment as an unregistered mineral and insists that the injured Romana accompanies him to his castle. Once there, it become apparent that Grendel believes she is an android. This assumption is based on her exact physical resemblance to the captive Strella — and Romana too is imprisoned like the Princess.

The swordsmen Zadek and Farrah have meanwhile recruited the Doctor to the party of Prince Reynart. He agrees to help repair an android copy of the Prince which is to be used to help him reach his throne and crown by diverting the attention of Grendel’s men while the real Prince slips into the coronation chamber through a back way. This plot looks plausible, but Grendel strikes first, drugging the Prince’s retinue and kidnapping Reynart himself. When the Doctor and the swordsmen recover they decide to change the original plan and crown the android Reynart instead. The party move through the tunnels beneath the royal castle to get to the throne room so that the facsimile Reynart can be crowned, for if he is not there at the correct moment then Grendel may be chosen under the law to claim the crown. The real Reynart was wounded in his capture and has been imprisoned with Romana at Castle Gracht to prevent any legitimate succession. By their elaborate ruse, the Doctor and his party succeed in getting the android Prince to the throne room and the coronation begins. However, the android Prince is damaged and it is clear the ruse will not hold for long. After the Prince is crowned King, Strella appears and swear loyalty to the King. Although struck by her resemblance to Romana, the Doctor realizes she is an android and hits her on the head with the King's sceptre.

K-9 is enlisted from the TARDIS to provide armed support and scanning intelligence that confirms that the Count has the Prince, the Princess, and Romana in his castle. Shortly afterward, Till, Grendel’s manservant, arrives at the Reynart estate and offers the Doctor a chance to collect Romana from the Pavilion of the Summer Winds, a nearby gazebo. It is, as ever, a trap. Grendel knows the Doctor is the man who has deprived him of the throne and has persuaded his android maker Madam Lamia, who is in love with him, to make an android in the image of Romana that is programmed to kill. While this is happening, the real Romana manages to escape from Castle Gracht and heads off to find the Doctor. She arrives at the Pavilion in the aftermath of Grendel’s attack, which has left Lamia dead, and helps the Doctor flee. The situation is soon reversed as Grendel succeeds in destroying the Reynart android and then recapturing the errant Romana. The evil Count now wishes Romana (as Strella) to marry the real King, who will then be killed, leaving Grendel free to take her hand himself and be declared the legitimate King of Tara.

Worried by the length of time a siege would take, the Doctor resorts to other means to get his friends back from Castle Gracht. K-9 is used to help them gain access to the castle by means of the moat and underground tunnels. The Doctor reaches the throne room just in time to stop the sham Reynart marriage to Romana. He then engages the Count in a deadly fight with electro-swords, defeating him and forcing the villain to jump into his own moat and swim for his survival.

Romana has meanwhile freed Strella and the royal party is united, with Grendel disgraced and presumably on his way to exile. It is a time of reunions: Reynart with his love Strella; and the Doctor and Romana with the fourth segment of the Key and the TARDIS – once K-9 has been retrieved from a boat in the moat.

Cast
Doctor Tom Baker (Fourth Doctor)
Companions John Leeson (K-9 Mk. II)
Mary Tamm (Romana I)
Guest stars
Neville Jason — Prince Reynart
Peter Jeffrey — Count Grendel
Simon Lack — Zadek
Paul Lavers — Farrah
Lois Baxter — Lamia
Martin Matthews — Kurster
Declan Mulholland — Till
Cyril Shaps — Archimandrite

Production
Writer David Fisher
Director Michael Hayes
Script editor Anthony Read
Producer Graham Williams
Executive producer(s) None
Production code 5D
Series Season 16
Length 4 episodes, 25 minutes each
Originally broadcast November 25–December 16, 1978

source; wikipedia

Series 16: The Stones of Blood

The Doctor and Romana are about to embark in search of the third segment of the Key to Time when an aural warning tells them to "Beware the Black Guardian." At this prompt the Doctor reveals Romana was not sent on this quest by the President of the Time Lords, but rather by the omni-powerful White Guardian, who wishes them to gather the Key to maintain galactic stability. They venture outside to find themselves near the Nine Travellers, a group of gromlech or standing stones in Boscombe Moor, Cornwall. Also interested in the location is aged archaeologist, Professor Amelia Rumford, who is surveying the stones along with her friend, Vivien Fay.

Alerted to the activities of a local druidic sect, the Doctor heads off to meet its implied leader, de Vries, who lives in a large property nearby, Boscombe Hall, built on the site of the Convent of the Sisters of St Gudula. Inside, de Vries and his maid Martha are incanting to the Cailleach, the Druidic goddess of war and magic. The Doctor interrupts and is entertained briefly by de Vries until his host sees the opportunity to knock him out. De Vries and his mistress, dressed in a hideous bird costume, aim to sacrifice him to the Cailleach, but are disturbed by Professor Rumford, who helps the Doctor get free.

At the same time Romana is wandering by the cliff edge when an apparition of the Doctor confronts her and she nearly falls over the edge. When the real Doctor saves her she is somewhat confused, but the newly arrived K-9 calms her by assuring Romana it is indeed the Doctor – and he is convinced of the existence of a projected doppelganger. He determines that de Vries can answer some questions, and sets off for Boscombe Hall. When he gets there he finds the owner and his maid dead, crushed to death and the place under attack by a pair of mobile giant stones like those from the Moor. The Doctor and K-9 repel the attack, though the robot is badly damaged and needs repair work in the TARDIS. Some more curious facts come to life: the Doctor works out that the stones are depend on globulin and therefore need blood to survive; and Romana has pieced together that the owners of the Hall and the preceding convent were all women. It soon becomes clear they all had the same face too – that of Vivien Fay.

Meanwhile the woman in the bird costume has brought more stones (or Ogri, as she calls them) to life using poured blood. Romana ventures back to the stone circle and there finds Miss Fay in the costume. When challenged, she fires a weapon at Romana which sends her to hyperspace. After destroying one of the stones which is pursuing them, the Doctor and Professor Rumford reach the stone circle they are told by Miss Fay that Romana will be safe providing the Doctor stops interfering, and then disappears. The Doctor now identifies the stones as Ogri, a life form from Ogros in the Tau Ceti system, and there are two of them still missing and moving around the countryside. Two innocent campers help quench their taste for blood.

The Doctor calculates Romana and her captor must be in hyperspace, and builds a projecting device which he uses to transmit himself there. He arrives on a hyperspace craft which appears to be a prison vessel. He soon breaks a lock on a sealed door, releasing two floating globes. They are Megara, justice machines - dispensing the law as judge, jury and executioner. They contend that as the Doctor broke the seals he has transgressed the law and should be eliminated.

K-9 and Amelia have meanwhile been tasked with protecting the projector used by the Doctor to cross the dimensions, but find themselves under attack from two of the Ogri. Vivien returns to Earth and destroys the device but spares her friend. She takes the Ogri back to the hyperspace vessel with her and there tells the Doctor and Romana she has destroyed their linking device between the dimensions, leaving them trapped in hyperspace though she, with her wand, can cross the dimensions easily. The Megara destroy one of the Ogri when it threatens them.

The Doctor now faces trial by the Megara, an abrupt and unfair process dependent on the word but not the spirit of the law. Conducting his own defence, he attempts to draw Vivien Fay into the trial and to get the Megara to subject her to truth indicators, surmising she is one of the criminals from the prison ship. He finds out that one of the prisoners the ship was carrying is Cessair of Diplos, a criminal wanted for murder and the removal and misuse of the Great Seal of Diplos, which had the powers of transmutation, transformation, and the establishing of hyper spatial and temporal coordinates.

Amelia and K-9 have meanwhile repaired the projector and use the device to beam Romana back from the hyperspace vessel – plus the one surviving Ogri, which pursues them. They find some incriminating data at Miss Fay’s cottage and then Romana and the Ogri return to the spacecraft to await the verdict.

At the close of his trial, the Doctor is convicted and the Megara fire executing beams at him. He quickly drags Vivien into the beams’ focus, forcing the Megara to examine her to see if she is badly hurt. On doing so they find that she is indeed Cessair of Diplos. She is charged with her crimes when she awakes and the last Ogri is confined in a cell aboard ship to be returned to its own planet. Cessair is sentenced to confinement for 1500 years and perpetual imprisonment, both to run consecutively, and is turned into stone on Boscawen Moor.

After further questioning by the Megara on the matter of his delayed execution, the Doctor, K-9 and Romana return to the TARDIS, thanking Amelia for her great assistance. As he suspected the Great Seal of Diplos – removed from the Cessair’s neck before she was turned to stone - is the third segment of the Key to Time and he translates it to its proper form.

Cast
Doctor Tom Baker (Fourth Doctor)
Companions John Leeson (K-9 Mk. II)
Mary Tamm (Romana I)
Guest stars
Beatrix Lehmann — Professor Rumford
Susan Engel — Vivien Fay
Nicholas McArdle — De Vries
Elaine Ives-Cameron — Martha
James Murray, Shirin Taylor — Campers
David McAllister, Gerald Cross — Megara Voices

Production
Writer David Fisher
Director Darrol Blake
Script editor Anthony Read
Producer Graham Williams
Executive producer(s) None
Production code 5C
Series Season 16
Length 4 episodes, 25 minutes each
Originally broadcast October 28–November 18, 1978

source: wikipedia

Series 16: The Pirate Planet

The Key to Time tracer points the Doctor and Romana to the cold and boring planet of Calufrax, but when they arrive they find an unusual civilisation that lives in perpetual prosperity. A strange band of people with mysterious powers known as the Mentiads are feared by the society, but the Doctor discovers that they are good people but with an unknown purpose. He instead fears the Captain, the planet's leader and benefactor. After meeting the Captain on the bridge he learns that they are actually on a hollowed-out planet named Zanak, which has been materialising around other planets to plunder their resources.

After repairing Zanak's engines, which were damaged when the planet materialised in the same place as the TARDIS, the Captain plans to take Zanak to Earth. The Doctor finds the true menace controlling the Captain is the ancient tyrant Queen Xanxia, disguised as the Captain's nurse, who uses the resources mined from planets in an attempt to gain immortality. Despite the Captain's apparent insanity, he is a calculating person who plans to destroy Xanxia. The Mentiads learn that their psychic powers are strengthened by the destruction of entire worlds beneath their feet.

Throughout Zanak, the Key to Time locator has been giving odd signals that seem to indicate that the segment is everywhere. Once the Doctor and Romana see the Captain's trophy room of planets, they conclude that Calufrax is the segment that they are looking for. They use the TARDIS to once again disrupt Zanak's materialisation around Earth while the Mentiads sabotage the engines. Xanxia kills the Captain when he finally turns against her. The Doctor, Romana, and the Mentiads destroy Zanak's bridge and Queen Xanxia, ending the devastation caused by Zanak's travels.

Cast
Doctor Tom Baker (Fourth Doctor)
Companions John Leeson (K-9 Mk. II)
Mary Tamm (Romana I)
Guest stars
Bruce Purchase — The Pirate Captain
Andrew Robertson — Mr Fibuli
Rosalind Lloyd — The Nurse
David Warwick — Kimus
David Sibley — Pralix
Ralph Michael — Balaton
Primi Townsend — Mula
Clive Bennett — Citizen
Bernard Finch — Mentiad
Adam Kurakin — Guard

Production
Writer Douglas Adams
Director Pennant Roberts
Script editor Anthony Read
Producer Graham Williams
Executive producer(s) None
Production code 5B
Series Season 16
Length 4 episodes, 25 minutes each
Originally broadcast September 30–October 21, 1978

source: wikipedia

Series 16: The Ribos Operation

The White Guardian recruits the Doctor to collect the six hidden and disguised segments of the powerful Key to Time. He assigns him an assistant Time Lady named Romanadvoratrelundar, whom the Doctor calls Romana (despite Romana's preference for "Fred" when given a choice by the Doctor). He warns him that the Black Guardian also seeks these segments, but for an evil purpose. The White Guardian provides them with a wand-like device which can locate the pieces and remove their disguise. When inserted into the TARDIS console, the locator reveals a segment to be on Cyrrenhis Minima, but then the signal moves to Ribos.

Ribos is an icy planet with late-medieval-type inhabitants who are unaware of alien cultures. A human from Earth named Garron tries to sell Ribos to an exiled tyrant called the Graff Vynda-K. The Graff is impressed by the planet's supposed quantity of jethrik, the rarest and most valued mineral in the galaxy. He believes the opportunity confirmed when he sees a piece of jethrik besides the Ribos crown jewels. This is all part of a ruse orchestrated by Garron; the jethrik was planted by Garron's assistant Unstoffe. The locator points the Doctor and Romana to the same jethrik, which must be the disguised segment of the Key to Time.

The Graff Vynda-K provides a large sum of money for the planet upfront that is to be kept safely in the room with the crown jewels, watched by Ribos guards by day and a shrivenzale beast by night. Later, Unstoffe distracts the shrivenzale, recovers their piece of jethrik, and takes the money from the safe. The Graff learns of Garron's deception when he discovers a covert listening device in his room. He takes Garron hostage with his "accomplices" the Doctor and Romana, and he starts the search for Unstoffe, who still has the money and the jethrik. Unstoffe hides with Binro, a homeless outcast who believes that Ribos is a planet orbiting a star, which Unstoffe confirms to be true. The Ribos guards summon a Seeker who locates Unstoffe's hideout. Using the listening device in the Graff's room, Garron warns Unstoffe about the Graff. Binro, thankful for Unstoffe's encouragement, leads him to the labyrinthine Catacombs under the city.

The Graff and his men enter the Catacombs without the Ribos guards, who fear the place. K-9 helps the Doctor, Romana, and Garron to escape from the Graff's quarters and go to the Catacombs. The Ribos guards destroy the entrance to the Catacombs causing the ceiling to collapse on the Graff's men. With the money and the piece of jethrik, the Graff gives his last surviving guard an explosive to kill himself with. The guard, actually the Doctor in disguise, swaps the explosive for the jethrik. The Graff walks off into the maze yelling like a madman before exploding. After leaving the Catacombs, the Doctor, Romana, and K-9 dematerialize in the TARDIS. Garron and Unstoffe are free to the Graff's deserted ship and the Doctor and Romana reveal the first piece of the Key to Time.

Cast
Doctor Tom Baker (Fourth Doctor)
Companions John Leeson (K-9 Mk. II)
Mary Tamm (Romana I)
Guest stars
Cyril Luckham — The Guardian
Iain Cuthbertson — Garron
Nigel Plaskitt — Unstoffe
Paul Seed — Graff Vynda-K
Robert Keegan — Sholakh
Timothy Bateson — Binro
Anne Tirard — The Seeker
Prentis Hancock — Shrieve Captain
Oliver Maguire, John Hamill — Shrieves

Production
Writer Robert Holmes
Director George Spenton-Foster
Script editor Anthony Read
Producer Graham Williams
Executive producer(s) None
Production code 5A
Series Season 16
Length 4 episodes, 25 minutes each
Originally broadcast September 2–September 23, 1978

source; wikipedia