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The Fourth Doctor (1974-1981)
Season 
Twelve (1974-75) Season Twelve (1974-75): Bohemian Rhapsody
First appearances of Harry and the creator of the Daleks, Davros.

Season Sixteen (1978-79): The Quest For The Key To Time
First appearances of Romana and the Black and White Guardians.
Season 
Sixteen (1978-79)
Season 
Thirteen (1975-76) Season Thirteen: A Gothic Aspect (1975-76)
First appearance of the Zygons.
Season Seventeen (1979-80): The Time Traveller's Guide To The Galaxy
Romana regenerates into her second incarnation.
Season 
Seventeen (1979-80)
Season 
Fourteen (1976-77) Season Fourteen (1976-77): Savagery
First appearances of Leela, Borusa and the skeletal Master.
Season Eighteen (1980-81): Change And Decay
First appearances of Adric, Nyssa, Tegan and the revitalised Master.
Season 
Eighteen (1980-81)
Season 
Fifteen (1977-78) Season Fifteen (1977-78): A Lighter Touch
First appearance of K-9.

Season Twelve (1974-75): Bohemian Rhapsody

The Doctor
The Fourth 
Doctor Tom Baker played the Doctor from Robot in December 1974 to Logopolis in March 1981. He returned for Dimensions In Time in November 1993.

Companions and Recurring Characters

Harry Sullivan was a Surgeon Lieutenant attached to UNIT.

Ian Marter played Harry from Robot in December 1974 to Terror Of The Zygons in September 1975. He also returned for The Android Invasion in December 1975. Marter passed away in 1986.

Harry 
Sullivan

Davros was a scientist on Skaro who created the xenophobic Daleks.

Davros was played by Michael Wisher in Genesis Of The Daleks (March to April 1975); by David Gooderson in Destiny Of The Daleks (September 1979); by Terry Molloy in Resurrection Of The Daleks, Revelation Of The Daleks and Remembrance Of The Daleks (February 1984 to October 1988); and by Julian Bleach in The Stolen Earth / Journey's End and The Magician's Apprentice / The Witch's Familiar (June 2008 to September 2015).

Davros

The Production Team
Terrance Dicks had departed from Doctor Who at the end of the previous season, and was replaced by veteran Who scriptwriter Robert Holmes. Barry Letts remained in the producer's chair for just a single story during Season Twelve in order to ease the transition to his successor, Philip Hinchcliffe. Hinchcliffe and Holmes quickly discovered they shared a unique vision of Doctor Who. Having tired of the UNIT format, they sought to return the Doctor to his original role as a wanderer in time and space. They also wanted the programme to appeal to a more mature audience, and their adventures emphasised suspense and thrills, often cribbing from classic science-fiction and horror films and literature.

The Stories
Robot
Robot by Terrance Dicks, directed by Christopher Barry
When the secret plans to a disintegrator gun are stolen by what appears to have been some kind of giant robot, the newly-regenerated Doctor is quickly called in to investigate. The trail leads to a group of right-wing scientists at the Thinktank facility, who are seeking to use the robot and the disintegrator gun to impose their edicts on humanity. As the situation escalates, Sarah Jane may prove to be the Doctor's only means of influencing the robot.
Surgeon Lieutenant Harry Sullivan of UNIT leaves in the TARDIS with the Doctor and Sarah.
The Ark In 
Space
The Ark In Space by Robert Holmes, directed by Rodney Bennett
The TARDIS brings the Doctor, Sarah and Harry to the Nerva Beacon in the far future, where the remnants of humanity have been placed in suspended animation because of the risk of deadly solar flares on Earth. The humans have overslept by millennia, however, due to the incursion of the insect-like Wirrn. More Wirrn are gestating within Noah, the Beacon's leader, and as Noah starts to succumb to the alien influence, the human race faces imminent extinction.
The 
Sontaran Experiment
The Sontaran Experiment by Bob Baker and Dave Martin, directed by Rodney Bennett
The Doctor agrees to transmat down to Earth to make sure everything is okay before the Nerva survivors begin to reclaim their planet. There, he, Sarah Jane and Harry discover the presence of a Sontaran named Styre, who is performing cruel experiments on a band of captive humans. Styre's goal is to discover the weaknesses of the human body -- weaknesses the Sontarans will then exploit in their quest to dominate the universe.
Genesis Of 
The Daleks
Genesis Of The Daleks by Terry Nation, directed by David Maloney
The Time Lords intercept the Doctor, Sarah and Harry as they transmat back to Nerva, and send them to Skaro in the distant past in order to prevent the creation of the Daleks. There they discover the planet's two native races, the Kaleds and the Thals, are nearing the climax of the Thousand Year War. As the conflict reaches its terrible conclusion, Sarah discovers that a disfigured Kaled scientist named Davros has already accomplished what the time travellers were sent to stop: the genesis of the Daleks.
Revenge Of 
The Cybermen
Revenge Of The Cybermen by Gerry Davis, directed by Michael E Briant
The Doctor, Sarah and Harry return to the Nerva Beacon, but inadvertently appear thousands of years before they left. Whilst awaiting the arrival of the TARDIS, they discover the Beacon -- at this point in time used to direct interstellar traffic -- is overrun by a plague which has wiped out most of the crew. The culprits are the Cybermen, on a vendetta to destroy the deciding factor in humanity's war against them: Voga, the Planet of Gold.

Making History
With the introduction of the Fourth Doctor and the beginnings of the highly successful Hinchcliffe/Holmes tandem, Doctor Who saw its viewing figures reach new heights. For the first time ever, the start of a season was pushed forward, with Season Thirteen due to start in the fall rather than the subsequent winter. As a result, Season Twelve lost one story, Terror Of The Zygons, which was held back to the start the next season.

Season Thirteen (1975-76): A Gothic Aspect

The Stories
Terror Of 
The Zygons
Terror Of The Zygons by Robert Banks Stewart, directed by Douglas Camfield
The Brigadier summons the Doctor back to Earth to investigate mysterious goings-on around Loch Ness in Scotland. The Doctor, Sarah Jane and Harry discover that the Loch Ness Monster is no myth -- in fact, it is really the Skarasen, a cybernetic reptile used as a servant by shape-shifting aliens known as the Zygons. The Zygons are paving the way for an invasion of Earth, and have already used their powers to infiltrate the local authorities.
Harry decides to stay behind on Earth.
Planet Of 
Evil
Planet Of Evil by Louis Marks, directed by David Maloney
The Doctor and Sarah land on Zeta Minor, at the very edge of the universe. A scientific team led by Professor Sorenson is being terrified by an anti-matter monster, a situation which deteriorates when Sorenson takes a sample of anti-matter off-planet. The Doctor must stop Sorenson, who has begun mutating into a Jekyll-and-Hyde-like anti-man, and restore the balance on Zeta Minor before death comes calling for them all.
Pyramids Of 
Mars
Pyramids Of Mars by Lewis Griefer, directed by Paddy Russell
It is 1911, and the TARDIS lands in the home of sibling scientists Laurence and Marcus Scarman. Laurence desperately needs the Doctor's help, since his brother has been behaving very oddly ever since returning from an archaeological dig in Egypt. To confuse matters further, Laurence has begun detecting strange radio signals from the surface of Mars. The Doctor discovers that Marcus has become the avatar on Earth of Sutekh, a powerful alien Osirian imprisoned centuries earlier by his people for his terrible crimes. Now Sutekh is using Marcus to regain his freedom, and herald the end of the world.
The Android 
Invasion
The Android Invasion by Terry Nation, directed by Barry Letts
The TARDIS seems to have returned the Doctor and Sarah Jane to modern-day England, but it quickly becomes apparent that something is very wrong: the people behave oddly, the calendar has just one day on it, coins are all minted from the same date. The time travellers soon realise that they are not on Earth at all, but on a simulacrum created by the Kraals, who are using the replicated village to help them prepare for their imminent invasion of Earth.
The Brain Of 
Morbius
The Brain Of Morbius by Robin Bland, directed by Christopher Barry
The Time Lords divert the Doctor and Sarah to Karn. The planet is home to the Sisterhood of the Flame, whose sacred fire -- which provides an elixir granting them eternal life and is used by the Time Lords to aid in regenerative crises -- is slowly dying. The Sisterhood believes the Doctor has come to steal the vestiges of the elixir and has him captured. Also on Karn, meanwhile, is the mad Doctor Solon, who has covertly taken possession of the brain of Morbius, an evil Time Lord thought to have been executed. Solon is trying to build a new body for Morbius, and is lacking only a suitable head: the head of a Time Lord.
The Seeds Of 
Doom
The Seeds Of Doom by Robert Banks Stewart, directed by Douglas Camfield
An Antarctic expedition unearths two pods which the Doctor recognises as Krynoids. Once germinated, the pods will infect humans, turning them into giant carnivorous plants which will quickly overrun the world. The Doctor and Sarah Jane manage to destroy one Krynoid, but the other is stolen by an insane botanist named Harrison Chase, who intends to use the alien entity to help plants take over the world.

Making History
Amidst Doctor Who's soaring popularity, a new problem reared its head in the form of Mary Whitehouse and her National Viewers And Listeners Association (NVALA). A self-appointed media watchdog, Whitehouse had at times spoken out against violence and horror in Doctor Who in the past. With the Hinchcliffe/Holmes formula encouraging these very elements, Whitehouse went on the offensive, ultimately contributing to the break-up of the successful production team.

Season Fourteen (1976-77): Savagery

Companions and Recurring Characters

Leela was a far-future human whose culture had regressed to prehistorical standards, and who assisted the Doctor in defeating the mad computer Xoanon.

Louise Jameson played Leela from The Face Of Evil in January 1977 to The Invasion Of Time in March 1978. She returned for Dimensions In Time in November 1993.

Leela

The Stories
The Masque Of 
Mandragora
The Masque Of Mandragora by Louis Marks, directed by Rodney Bennett
The TARDIS accidentally transports the Mandragora Helix, a malevolent energy being, to Italy during the Renaissance. There, the Doctor and Sarah Jane become embroiled in court intrigue between the wicked Count Federico and his nephew, Giuliano. Meanwhile, the Helix gains the loyalty of the twisted astrologer Hieronymous, and plans to return humanity to the Dark Ages by murdering the great thinkers of the fifteenth century.
The Hand Of 
Fear
The Hand Of Fear by Bob Baker and Dave Martin, directed by Lennie Mayne
An explosion in a quarry unearths a calcified hand, which is inadvertently discovered by Sarah. The hand contains the consciousness of a silicon-based alien called Eldrad, who seizes control of Sarah's mind and compels her to break into a nuclear reactor, where he is able to regenerate his entire body. Eldrad then convinces the Doctor to return him to his homeworld of Kastria, from which he claims to have been wrongfully exiled. But there is far more to Eldrad's past than he is letting on...
The Doctor receives an urgent summons to Gallifrey and is forced to leave Sarah behind on Earth.
The Deadly 
Assassin
The Deadly Assassin by Robert Holmes, directed by David Maloney
The President of the High Council of the Time Lords is assassinated, and the Doctor, newly returned to Gallifrey, is the prime suspect. But the Doctor knows someone is framing him, and must rely on the help of the reluctant Castellan Kelner to unveil a traitor in the High Council. Ultimately, the trail leads to the dying, vengeful Master, who wishes to harness the powers of Rassilon's greatest discovery, the mythical Eye of Harmony. But to do so would mean the destruction of Gallifrey, and to prevent this, the Doctor must risk his life in the surreal landscape of the Matrix.
The Face Of 
Evil
The Face Of Evil by Chris Boucher, directed by Pennant Roberts
The TARDIS lands on a planet where the population is divided into two warring factions: the barbaric Sevateem and the brilliant Tesh. The Doctor himself is regarded as a demon by the Sevateem, and to the Time Lord's consternation, he discovers that a giant carving of the Evil One is in fact a replica of his own head. With the help of a Sevateem warrior named Leela, the Doctor discovers that the Sevateem god, Xoanon, is really a schizophrenic computer, whose malfunction is the fault of the Doctor himself.
Seeking adventure, Leela leaves with the Doctor.
The Robots Of 
Death
The Robots Of Death by Chris Boucher, directed by Michael E Briant
The TARDIS brings the Doctor and Leela to a Sandminer, a giant mining ship. The crew of the Sandminer is slowly being killed off one by one, and the time travellers are the obvious suspects. But the Doctor discovers that the impossible is coming true: the Sandminer's robot workers and manservants are responsible for the deaths, having fallen under the influence of the crazed scientist Taren Capel, who wishes to supplant the human race with his robotic creations.
The Talons Of 
Weng-Chiang
The Talons Of Weng-Chiang by Robert Holmes, directed by David Maloney
The Doctor and Leela find themselves in Victorian London. Girls are being kidnapped off the street, ghosts have been sighted in the opera house run by Henry Jago, and giant rats haunt the London sewers. At the centre of the chaos is a mysterious Oriental magician named Li H'sen Chang. Chang serves a man he believes is the god Weng-Chiang, and is searching for a cabinet lost by his master. The Doctor uncovers the truth, however -- Weng-Chiang is actually Magnus Greel, a tyrant from the 60th century whose escape back through time has transformed him into a disfigured monster.

Making History
As Doctor Who's ratings escalated, so too did criticism from the persistent Mary Whitehouse. After episode three of The Deadly Assassin concluded with a twenty-second-long freeze frame of the Doctor being drowned, Whitehouse finally won an admission from the BBC that the sequence had been excessively horrifying. Behind the scenes, it was decided that Philip Hinchcliffe should move on from the series, and that his successor should approach Doctor Who with a more light-hearted vision.

Season Fifteen (1977-78): A Lighter Touch

Companions and Recurring Characters

K-9 was a mobile computer in the shape of a dog, invented by Professor Marius.

K-9 appeared from The Invisible Enemy in October 1977 to Warriors' Gate in January 1981. He returned for The Five Doctors in November 1983, Dimensions In Time in November 1993, School Reunion in April 2006, and Journey's End in July 2008. K-9 was voiced by John Leeson in all stories except those between The Creature From The Pit and Shada, when he was voiced by David Brierley.

K-9

The Production Team
With Philip Hinchcliffe shifted off of Doctor Who onto more hard-hitting dramas which, it was perceived, would make better use of his talents, Graham Williams was brought in to both replace Hinchcliffe and to find a way to rework Doctor Who. Williams was under direct orders to tone down on the horror and violence, and as such replaced them with the only element he felt was remaining to him: humour. Robert Holmes, meanwhile, was also expressing a desire to leave so that he could return to scriptwriting full time. His mid-season replacement was Anthony Read.

The Stories
Horror Of 
Fang Rock
Horror Of Fang Rock by Terrance Dicks, directed by Paddy Russell
The TARDIS materialises near a lighthouse on an island in the English Channel, where a boat carrying several high-society passengers has just capsized. The lighthouse itself has suffered mysterious energy drains and the death of one of its technicians. The Doctor and Leela discover that a shapeshifting Rutan has infiltrated the island and is about to summon its mothership to Earth. As the lighthouse's occupants are killed off one by one it appears that, this time, the Doctor may be too late to save anyone.
The Invisible 
Enemy
The Invisible Enemy by Bob Baker and Dave Martin, directed by Derrick Goodwin
A parasite infects the Doctor whilst the TARDIS is hovering in space, and begins to slowly take over his mind. While the Doctor places himself in a coma to stall the organism, Leela takes the Time Lord to a medical facility on Titan in the far future. There, with the help of Professor Marius and his robot dog K-9, Leela has miniaturised clones of herself and the Doctor created, so that they can travel into the Doctor's brain and take the battle to the parasite itself.
Professor Marius gives K-9 to the Doctor and Leela.
Image Of The 
Fendahl
Image Of The Fendahl by Chris Boucher, directed by George Spenton-Foster
The activation of a time scanner draws the Doctor, Leela and K-9 to modern-day Earth, where a team of scientists has uncovered an ancient skull. The skull is that of the Fendahl, a creature which thrives on death and which was thought to have been destroyed by the Time Lords. One of the scientists, Thea Ransome, is converted into a host for the Fendahl, and she creates minions -- the deadly Fendahleen -- to deliver her lethal message across the planet.
The Sun 
Makers
The Sun Makers by Robert Holmes, directed by Pennant Roberts
The TARDIS lands on Pluto in the far future, where the Doctor is astonished to find the planet inhabited by humans and heated by a number of miniature suns. He, Leela and K-9 discover that the human race has been moved off Earth to do the bidding of the Company, a ruthless intergalactic conglomerate. It is up to the Doctor to uncover the secret of the Company's head, the Collector, while Leela is sentenced to death by steaming.
Underworld
Underworld by Bob Baker and Dave Martin, directed by Norman Stewart
The Doctor, Leela and K-9 find themselves in a spacecraft piloted by the last of the Minyans, a race which destroyed itself using technology given to them by early Time Lords. Now the remaining Minyans are on a desperate search for their race banks, lost centuries earlier, which represent the only hope for the survival of their civilisation. With the Doctor's help, the race banks are located. But in order to retrieve them, the time travellers must confront an insane computer and its robotic servants, or the Minyans will be forever doomed.
The 
Invasion Of Time
The Invasion Of Time by David Agnew, directed by Gerald Blake
The Doctor returns to Gallifrey, having become President of the High Council following an illicit deal with aliens known as the Vardans. He has Leela exiled to the wastes beyond the Capitol, where she allies herself with outcast Time Lords living as savages. Leela believes the Doctor has turned traitor, but in fact he is masterminding an elaborate plan to unveil the identity of the Vardans' masters, and foil a scheme to invade Gallifrey itself.
Leela remains on Gallifrey to marry a Chancellery Guard named Andred. K-9 stays with her, while the Doctor activates K-9 Mark II.

Making History
Season Fifteen saw an attempt not to just to lighten the atmosphere of Doctor Who but also to turn it back into more of a family show than it had been during the Hinchcliffe/Holmes era. This is most apparent in the introduction of K-9, designed to appeal mostly to younger children. With the measures taken by Williams this year, the attacks from Mary Whitehouse finally abated, and such criticisms would not plague Doctor Who again in any serious form until 1985.

Season Sixteen (1978-79): The Quest For The Key To Time

Companions and Recurring Characters

The first incarnation of the Time Lady Romanadvoratrelundar -- called Romana for short -- was despatched by the White Guardian to assist the Doctor in his quest for the Key to Time.

Mary Tamm played Romana from The Ribos Operation in September 1978 to The Armageddon Factor in February 1979.

The 
First Romana

The White Guardian was a cosmic force that strove for order and balance in the universe.

Cyril Luckham played the White Guardian on a recurring basis from The Ribos Operation in September 1978 to Enlightenment in March 1983.

The White Guardian

The Black Guardian was the White Guardian's antithesis, embodying chaos.

Valentine Dyall played the Black Guardian on a recurring basis from The Armageddon Factor in February 1979 to Enlightenment in March 1983.

The Black Guardian

The Stories
The Ribos 
Operation
The Ribos Operation by Robert Holmes, directed by George Spenton-Foster
The Doctor is called upon by the White Guardian, the embodiment of order and light, to find the six disguised segments of the Key To Time -- scattered throughout time and space -- so that the Guardian can restore the faltering universal balance. To this end, the White Guardian provides the Doctor with a new assistant in the form of the young Time Lady Romana. Their first destination is Ribos, a mediaeval-style planet which a con man named Garron is trying to sell to the megalomaniacal Graff Vynda-K. When the Graff uncovers Garron's treachery, the crook's assistant, Unstoffe, flees into the monster-infested Catacombs, little realising that amongst his possessions is the first segment of the Key To Time.
The White Guardian sends Romana to aid the Doctor.
The Pirate 
Planet
The Pirate Planet by Douglas Adams, directed by Pennant Roberts
The Doctor and Romana head to the planet Calufrax in search of the second segment of the Key To Time. Inexplicably, however, the TARDIS lands on Zanak. The Doctor discovers that Zanak is a pirate planet, materialising around other worlds and reaping their mineral wealth. The leader of this operation is the crazed Captain, who is prepared to take Zanak onto its next conquest: Earth.
The Stones Of 
Blood
The Stones Of Blood by David Fisher, directed by Darrol Blake
The quest for the third segment of the Key To Time takes the TARDIS to modern-day Earth, near a stone circle called the Nine Maidens. The circle has been the site of renewed worship of a Druidic goddess called the Cailleach, and has also attracted the interest of archaeologist Emilia Rumford. When someone tries to kill Romana, the Doctor realises that something is amiss at the Nine Maidens, and that the Cailleach may not be quite as mythical as he believed.
The Androids 
Of Tara
The Androids Of Tara by David Fisher, directed by Michael Hayes
While the Doctor has a rest, Romana finds the fourth segment of the Key To Time on Tara, only to be kidnapped by the villainous Count Grendel. It transpires that Romana is an exact double of Tara's Princess Strella. Grendel has aspirations to the Taran throne, and has kidnapped Strella in an attempt to force her to marry him; now he believes he can make Romana pose as Strella and accomplish the deception that way. But the Doctor allies himself with Reynart, Strella's true love, in a desperate attempt to stop the throne from falling into Grendel's cruel grasp.
The Power Of 
Kroll
The Power Of Kroll by Robert Holmes, directed by Norman Stewart
For the fifth segment of the Key To Time, the Doctor and Romana travel to the marsh moon of Delta Magna. There, the time travellers become enmeshed in tensions between the barbaric native Swampies, the gun-runner Rohm-Dutt, and the crew of a refinery which is trying to drive the Swampies away. In the midst of all this, the Swampie god, a gargantuan squid named Kroll, is beginning to stir, and even the Doctor will be defenseless in the wake of the destruction wrought by Kroll.
The 
Armageddon Factor
The Armageddon Factor by Bob Baker and Dave Martin, directed by Michael Hayes
The Black Guardian, the embodiment of evil and darkness, is closing in as the Doctor, Romana and K-9 go in search of the sixth and final segment of the Key To Time on the wartorn planet Atrios. Atrios is in a state of perpetual conflict with its neighbour, Zeos, and the planet's entire civilisation is being held together only through the tireless efforts of Princess Astra. But it soon becomes clear that there is more to the Atrios-Zeos war than meets the eye, and discovering the key to the mystery may become the deciding factor in the Doctor's quest for the Key To Time.

Making History
An idea Graham Williams had tried and failed to implement during his first year as producer was that of an overarching theme running through every story of the season. This finally came about during Season Sixteen, with the Doctor's quest for the Key playing a greater or lesser role in all six adventures.

Season Seventeen (1979-80): The Time Traveller's Guide To The Galaxy

Companions and Recurring Characters

Despite having completed the quest for the Key to Time, Romana chose to continue travelling with the Doctor in a regenerated body.

Lalla Ward played Romana from Destiny Of The Daleks in September 1979 to Warriors' Gate in January 1981. She returned for Dimensions In Time in November 1993.

The 
Second Romana

The Production Team
Anthony Read left Doctor Who at the end of Season Sixteen. His replacement was the inexperienced but creative Douglas Adams, who had scripted The Pirate Planet the previous year. Remaining on the programme for just a single season, Adams would shortly gain great fame and prestige for his radio play/novel/TV series (and, posthumously, feature film) The Hitchhiker's Guide To The Galaxy.

The Stories
Destiny Of 
The Daleks
Destiny Of The Daleks by Terry Nation, directed by Ken Grieve
Having installed a Randomiser in the TARDIS to avoid the attentions of the Black Guardian, the Doctor and the newly-regenerated Romana find themselves on a bleak planet the Doctor is sure he has visited before. The two are separated in a cave-in, and Romana finds herself a captive of the Doctor's oldest foes, the Daleks. The Doctor encounters the Daleks' enemies, the ruthless android Movellans, who reveal that the planet is in fact Skaro. The Daleks are searching for their long-lost creator, Davros, in an attempt to shatter the stalemate in the Dalek-Movellan war.
Romana regenerates into her second incarnation.
City Of 
Death
City Of Death by David Agnew, directed by Michael Hayes
In modern-day Paris, the Doctor and Romana realise that someone is playing with time. They trace the disturbances to Count Scarlioni, who is actually one of several fragments of an alien Jagaroth named Scaroth. Scaroth's ship exploded on primordial Earth, scattering shards of his being throughout history. Now Scaroth has accumulated the funds and technology to send himself back in time to avert the accident. But the Doctor realises that this would prevent the evolution of life on Earth, which was instigated by the explosion.
The Creature 
From The Pit
The Creature From The Pit by David Fisher, directed by Christopher Barry
The planet Chloris is plentiful in vegetation but barren of metal. When the Doctor, Romana and K-9 arrive, Chloris' leader, the wicked Adrasta, has the Doctor thrown into a pit at the bottom of which an enormous green monster is supposed to dwell. The Doctor discovers that the monster is actually Erato, an ambassador from Tythonus who came to Chloris to trade metal for agriculture and was banished to the pit because Adrasta feared losing her monopoly on metal. But this revelation may come too late, as the Tythonians are en route to Chloris, ready to ravage the planet to avenge Adrasta's treatment of their envoy.
Nightmare Of 
Eden
Nightmare Of Eden by Bob Baker, directed by Alan Bromly and Graham Williams
Two spaceships collide in hyperspace, fusing the vessels together. Investigating the accident, the Doctor, Romana and K-9 meet Tryst, an eccentric scientist who is carrying samples of various planets within a machine called the Continuous Event Transmuter. The CET malfunctions, however, unleashing monstrous Mandrels onto both ships. Meanwhile, the time travellers discover that someone on board has been smuggling the illicit, addictive drug vraxoin -- and it becomes clear that the disastrous events are not unrelated.
The Horns Of 
Nimon
The Horns Of Nimon by Anthony Read, directed by Kenny McBain
The Doctor and Romana discover a stricken space vessel transporting seven young people from the planet Aneth to Skonnos. The Time Lords are forced to help repair the ship, even though the Anethans are fated to be sacrificed to the bull-like Nimon, who has promised the Skonnans great prosperity. On Skonnos, however, the Doctor learns that the Nimon is actually a member of a race of intergalactic locusts, who ravage each world foolish enough to believe their lies.
Shada
Shada by Douglas Adams, directed by Pennant Roberts
The Doctor, Romana and K-9 visit an old friend, a retired Time Lord named Professor Chronotis now living as a professor in Cambridge. There they encounter the evil scientist Skagra, who has come to steal a Gallifreyan text in Chronotis' possession. With the book, Skagra can locate Shada, the Gallifreyan prison planet, where he intends to force Salyavin, a Time Lord criminal with vast mental powers, to help him imprint his mind upon every being in the cosmos.

Making History
Although Doctor Who had been threatened by strikes before, never had a story actually been cancelled due to industrial action until Season Seventeen. Sadly, the loss of Shada also meant that the planned conclusion to the departing Graham Williams' production era would never see broadcast. It would, however, finally see the light of day as a video release in 1992.

Season Eighteen (1980-81): Change And Decay

Companions and Recurring Characters

Adric was a teenaged mathematical genius who stowed away aboard the TARDIS after helping the Doctor solve the mystery of his home planet, Alzarius.

Matthew Waterhouse played Adric from Full Circle in October 1980 to Earthshock in March 1982. He returned as a hallucination for Time-Flight in March 1982 and as a regenerative image for The Caves Of Androzani in March 1984.

Adric

Nyssa, the daughter of nobility on the planet Traken and a gifted scientist, joined the Doctor after her father was murdered by the Master.

Sarah Sutton played Nyssa from The Keeper Of Traken in January 1981 to Terminus in February 1983. She returned for Dimensions In Time in November 1993, and also as a regenerative image for The Caves Of Androzani in March 1984.

Nyssa

The evil Time Lord known as the Master was reinvigorated after stealing a human body, embarking on a new spree of mayhem across space and time.

Anthony Ainley played the Master on a recurring basis from The Keeper Of Traken in February 1981 to Survival in December 1989.

The Master

Tegan Jovanka was an airline stewardess for Air Australia who wandered into the TARDIS when it was parked in 1980s London.

Janet Fielding played Tegan from Logopolis in February 1981 to Resurrection Of The Daleks in February 1984. She returned as a regenerative image for The Caves Of Androzani in March 1984.

Tegan

The Production Team
As Doctor Who headed into the 1980s, an all-new production team was brought in to helm the series. The new producer was John Nathan-Turner, who would go on to serve in this capacity for the entire decade. His script editor for Season Eighteen was Christopher H Bidmead. The new team's philosophy was that Doctor Who had strayed too far into the realm of science fantasy rather than proper science-fiction in recent years; the new season would see a return to solid science more in line with this way of thinking.

The Stories
The Leisure 
Hive
The Leisure Hive by David Fisher, directed by Lovett Bickford
In search of a holiday, the Doctor and Romana travel to the famous Leisure Hive on Argolis, a planet ravaged by a nuclear war with the reptilian Foamasi years earlier. The main attraction of the Hive is a device called the Tachyon Recreation Generator, but when things start to go mysteriously wrong with the machine, the Doctor realises that evil is afoot in the Hive. He and Romana begin to unearth a tangled conspiracy which may lead to a new, deadlier war between the Argolins and the Foamasi.
Meglos
Meglos by John Flanagan and Andrew McCulloch, directed by Terence Dudley
The Doctor is summoned back to the planet Tigella, where the population is divided along religious and scientific lines. Something is going terribly wrong with Tigella's main power source, the Dodecahedron, but the Savants are prevented from investigating by the zealous Deons. To make matters worse, before the Doctor can solve the problem with the Dodecahedron, he is accused of its theft. The true culprit is Meglos, a shapeshifting Zolfa-Thuran, who intends to unleash the full might of the Dodecahedron upon the universe.
Full 
Circle
Full Circle by Andrew Smith, directed by Peter Grimwade
Romana is recalled to Gallifrey, but en route the TARDIS is drawn through a Charged Vacuum Emboitment into another universe, called E-Space. Landing on the planet Alzarius, the Doctor meets a group of humans who are trying to rebuild their spacecraft -- which crashlanded generations ago -- so they can return to their native Terradon. When Marshmen begin rising from the swamps during the dreaded time of Mistfall, however, the Doctor realises that there is something amiss on Alzarius, and begins to unravel a genetic riddle which stretches back centuries.
Adric, a young Alzarian, stows away on board the TARDIS.
State Of 
Decay
State Of Decay by Terrance Dicks, directed by Peter Moffatt
Still trapped in E-Space, the TARDIS materialises on a mediaeval planet. The townsfolk live in fear of the Three Who Rule, who govern from their mighty castle. Investigating, the Doctor discovers that the Three Who Rule are ancient astronauts who were turned into vampires long ago, and their castle is actually their spaceship. When Romana and Adric are kidnapped, the Doctor must ally himself with a band of renegade peasants to stop the resurrection of one of Gallifrey's greatest enemies: the Great Vampire itself.
Warriors' 
Gate
Warriors' Gate by Steve Gallagher, directed by Paul Joyce
Trying to escape from E-Space, the Doctor, Romana, Adric and K-9 instead land in an eerie white void whose only feature is a crumbling old keep. Also trapped in the void is a privateering ship captained by the cruel Rorvik, whose time sensitive pilot, the leonine Tharil Biroc, escapes and lures the Doctor into the keep and the mirror gateway beyond. There, the Doctor witnesses the rise and fall of the once-mighty Tharil Empire. He realises that he must free the Tharils enslaved on the privateering ship and escape through the gateway, before Rorvik's vengeful actions destroy them all.
Romana and K-9 remain in E-Space to help free the captive Tharil race.
The Keeper Of 
Traken
The Keeper Of Traken by Johnny Byrne, directed by John Black
The Union of Traken is governed by a Keeper gifted with the powers of the Source. The current Keeper is nearing the end of his thousand-year tenure, however, and asks the Doctor and Adric -- who have escaped from E-Space -- to go to Traken and stop an evil he believes is plotting to destroy the Union. But the source of the evil, the Melkur, has already infiltrated the Consuls of Traken, and has the Doctor declared a criminal. Allying himself with Consul Tremas and his daughter, Nyssa, the Time Lord must uncover the true power behind the Melkur -- someone who knows the Doctor of old.
Warriors' 
Gate
Logopolis by Christopher H Bidmead, directed by Peter Grimwade
After her aunt is murdered by the Master, an airline stewardess named Tegan Jovanka becomes an unwitting stowaway aboard the TARDIS as it travels to the planet Logopolis. There, the Doctor discovers that the Master's interference with the Logopolitans' advanced mathematics has unleashed a wave of entropy which threatens to consume the entire universe. The two Time Lords enter into an uneasy alliance, together with Adric, Tegan and Nyssa, who has travelled to Logopolis to confront the Master. Their only hope lies on Earth... but then, in the moment of greatest crisis, the Master plays his ultimate trump card.
The Fourth Doctor, now joined in his travels by Nyssa and Tegan, falls from atop the Pharos Project telescope and regenerates.

Making History
The stylistic changes made for Season Eighteen saw Doctor Who enter firmly into the Eighties, much as the programme's reconceptualising at the start of Season Seven had ushered it into the Seventies. With a flashier title sequence, more high-concept stories, more accessible companions, and a renewed emphasis on production values (seen as taken an appreciable dip during Graham Williams' time on the show), Doctor Who had undergone a complete facelift. With the departure at the season's end of Tom Baker, the show's longest-serving Doctor, the slate was wiped clean for a new style of Doctor Who.