The one with malevolent sparkles.
Written by David Fisher. This four-episode serial first aired from October 28 to November 18, 1978.
The search for the Key To Time takes the Doctor, Romana and K-9 to present-day (well, 1970s) Earth, where the Tracer leads them to a group of standing stones on Boscome Moor. The third segment is nowhere to be found, and the travellers instead meet the elderly Professor Amelia Rumford and her live-in assistant Vivien Fay, who tell them that the site has had a varying number of stones over the years.
Then the inevitable campy druids show up and nearly sacrifice the Doctor, before it is revealed that the stones themselves are sentient — a lifeform called Ogri who feed on blood. One of the Ogri kills the head druid and it is revealed that Vivien Fay is in fact the Cailleach, a being worshipped by the druids, having taken on human form after being on Earth for four thousand years. Fay transports Romana to a spaceship hidden in hyperspace at the circle, and the Doctor follows.
Accidentally releasing two justice robots, the Doctor is sentenced to death. He takes a lawyer wig out of his pocket and instead begins a magnificent bit of Bothering by the Book. He manages to knock Fay unconscious by touching her just as he is supposed to be electrocuted, which legally allows the sparkly justice robots (called Megara) to read her mind, seeing as she can't speak for herself anymore. The Megara quickly notice that Fay is in fact Cessair of Diplos, the criminal they've actually been sent to try. She stole a few Ogri from a nearby planet and employed them on Earth as her bodyguards while avoiding the interstellar police for four thousand years. They transform her into the final stone in the circle, but not before the Doctor has snagged her necklace — the segment of the Key that he has been looking for.
- Agony of the Feet: Romana's addiction to style results in a terrible choice of footwear at the start of this story- stiletto heels in a place loaded with stones. The Doctor calls her out on this several times, and they start giving her much discomfort. Naturally, Romana rids herself of them and goes barefooted by the end of the first episode when the shoes prove too much for her. They become Chekhov's Gun when the Doctor discovers them discarded in a field. At the Doctor's insistence, she switches to more comfy and practical boots. But changes her whole outfit to match them.
- A.I. Is a Crapshoot: The Doctor's tale of justice machines, a group of hanging judges that are more proactive in ensuring his death than they are at preventing it.
- All Crimes Are Equal: Not exactly equal, but death is probably the most merciful, and definitely the most common sentence the Megara use.
- All Myths Are True: Gog, Magog, and ogres are all inspired by the Ogri, the Druids' blood sacrifices actually work by feeding the Ogri, and the Druids' goddess, the Cailleach, is a millennia-old alien fugitive who'd been manipulating British history for her own benefit.
- Alternate Landmark History: The Nine Travellers is the hiding place of an ancient astronaut and some of the stones are her Ogri servants.
- Ambiguously Gay: There's an implication of a romantic past between professors Fay and Rumford.
- Amoral Attorney: Even the Megara that's supposed to defend the Doctor pleads the death penalty.
- Ancient Astronauts: Cessair was an alien who also took on the identity of Vivien Fay, Morgana Le Fay, The Goddess and The Cailleach. Also her Ogri hid as some of the stones in the Nine Travellers and possibly the inspiration for ogres, Gog and Magog.
- And I Must Scream: Cessair's fate.
- Art Shift: Fourth and final Tom Baker serial shot entirely on video (director Darrol Blake had a dislike for the Video Inside, Film Outside look, although it did come in handy when the circle of stones had to be recreated in the studio for the sequences set at night, which would have been much more obvious had the daytime sequences been shot on film). The show would ditch film for good at the start of "The Trial of a Time Lord".
- Attack of the Killer Whatever: Killer, blood-drinking rocks that move around and kill villagers.
- Beat Them at Their Own Game: How the Doctor outwits the Megara.
- Big Bad: Cessair of Diplos.
- Bothering by the Book: Four once again shows his expertise at this.
- Bullfight Boss: The Doctor gets one of the Ogri to charge over the edge of a cliff this way, accompanied by Spanish background music.
- Call-Back: The spaceship has a dead Wirrn in it.
- Celtic Mythology
- Circle of Standing Stones: Although some of them are actually walking stones.
- Cool Old Lady: Professor Amelia Rumford. When going out to find the Doctor, she takes a policeman's truncheon with her.Romana: What's that?
Vivien: A policeman's truncheon. Last year, when she lectured in New York, she took it with her in case she got mugged.
Romana: And did she get mugged?
Vivien: No, she got arrested for carrying an offensive weapon.
- Courtroom Episode: IN SPACE! (episode 4).
- Cover Innocent Eyes and Ears: When the Doctor and K-9 discover the dead bodies of De Vries and Martha, the Doctor puts a hand over K-9's visual sensor.
- Crazy-Prepared: The Doctor just happens to have a barrister's wig in his pocket.
- Creepy Crows:
- Romana is spooked by a crow at the moor, and a pair later watch her from atop the TARDIS.
- De Vries keeps a raven at Boscombe Hall as part of his druid hobby, stating that ravens act as the eyes of the Cailleach, and freaks out when it disappears, assuming (correctly) that it's a portent of doom.
- Cuteness Proximity: The Doctor's insistence on treating K-9 like an actual dog is quickly taken up by Amelia as well.
- Druids: A group of them serve as the serial's decoy antagonists, providing blood sacrifices for the Ogri as a means of worshiping the Cailleach before being quickly disposed of once the Cailleach takes the reins of the story.
- Electronic Speech Impediment: When K-9 is damaged by the Ogri, some of his sentences end with the words slowing down and becoming distorted.
- Even Evil Has Loved Ones: Cessair is very careful to ensure that none of her actions harm Amelia.
- Everything's Better with Sparkles: The Megara are pretty much just sentient sparkles.
- Exposition of Immortality: There are three portraits missing from the wall at Boscombe Hall. The Doctor and Professor Rumford come across them later, revealing them to all be portraits of Vivien Fay painted at various points during her long existence on Earth.
- Failed a Spot Check: Everyone gets ambushed several times over by eight foot tall moving rocks.
- Glad I Thought of It: Romana tells the Doctor to get on with finding the next segment of Key to Time. The Doctor starts to leave, turns back, and tells her that he's decided to go find the location of the next segment of the Key to Time.
- Golem: The Ogri are a mix of this and Living Statue, since they're part of a stone circle.
- Gothic Horror: The first half of the story is one of the Graham Williams era's few forays into the genre, revolving around blood sacrifices made by a Druid cult. The second half, meanwhile, quickly disposes of the style in favor of a courtroom drama.
- Halfway Plot Switch: In which a Gothic Horror story about Druids and human sacrifice in a stone circle suddenly turns into a Black Comedy courtroom drama aboard a hyperspace ship.
- Hanging Judge: The Megara act according to a very strict legal code which not only mandates the death penalty for pretty much everything, but does little to avoid the accused from being put to death.
- Homoerotic Subtext: Earlier drafts of the script made it much more clear how Amelia Rumford and Vivian Fay spent their time in that cabin. Somewhat astonishingly, Mary Tamm (Romana) didn't notice until fans pointed it out to her, and her comment was "we were all so innocent back then..."
- Human Sacrifice: Well, the druids didn't know the Doctor wasn't human.
- I Have Many Names: Cessair, aka Vivien Fay, aka Morgana Le Fay, aka The Goddess, aka The Cailleach... need we go on?
- I Never Told You My Name: De Vries calls the Doctor by name the first time they meet. The Doctor later points out this trope, but De Vries never gets around to explaining how he knew.
- I'm a Doctor, Not a Placeholder: When K-9 tells Professor Rumford that she will need to repair the Doctor's plot device, she responds that she is an archaeologist, not an engineer.
- Is It Always Like This?: At the end of the story, Romana asks the Doctor if his visits to Earth always go like this. He replies that sometimes they're even exciting.
- Judge, Jury, and Executioner: The Megara.
- Judicial Wig: When arguing his case against the Megara, The Doctor puts one on.
- Kangaroo Court: The Megara are hardly impartial judges concerning their case against the Doctor, given that they are also his accusers. The most effort the one who volunteers to act as defence lawyer goes through is to try to argue for a painless execution, without making any real attempt to get his client off.
- Lawful Stupid: The Megara, who seek to execute the Doctor for letting them out without authorization, never mind that everyone who could grant it was long dead. Even after he catches the criminal they were sent to try, they still don't give him a reprieve, only a delay of sentence while they go to their next destination, after which they'll come back to enact sentence. The Doctor plans to be long gone by then.
- Literal Cliffhanger: Romana gets pushed off a cliff at the end of Episode One. Clearly a punishment for the Burberry hat and impractical shoes.
- Literal-Minded: K-9 as usual. Also Romana's reaction on hearing that Miss Fay used to be a brown owlnote .
- Meaningful Name: If you know your myths and legends, Vivian Fay.
- Mood Whiplash: The serial goes from a dark, gruesome horror story to a black comedy about malfunctioning justice robots.
- Our Ogres Are Hungrier: The Doctor suggests that Gog, Magog, and Ogre could be inspired by the Ogri, large rocks that feed on blood.
- Plot Allergy: Cessair, like all Diplosians, has an aversion to citric acid, which helps in discovering her true identity.
- Really 700 Years Old: Vivien Fay has been on earth for 4000 years.
- Rock Monster: The Ogri are giant moving stone pillars that feed on blood.
- Rubber-Forehead Aliens: In her true Diplosian form, Cessair looks just like she did as Vivien Fay, except with silver skin and sparkly Greco-Roman robes.
- Sealed Evil in a Can: A slight variation happened, where the Doctor releases a pair of biomechanical judges called the Megara from a ship stranded in hyperspace, and the judges promptly sentence him to death for letting them free without the proper legal authorization.
- Secret Passage: The manor house has a secret room with a door hidden in the wall panelling and opened by a switch hidden in the decorative border of the fireplace.
- Silicon-Based Life: The Ogri.
- Some Kind of Force Field: When the Doctor confronts Cessair, she warns him not to come too close; when he does anyway, there's a strange noise and he exposits that she's surrounded by a force field. (Specifically, "a very primitive force field" — to which she responds, "but so very effective".)
- Spark Fairy: The Megara.
- Starfish Aliens: The Ogri.
- Stripped to the Bone: The Ogri can do this to anyone who touches them.
- Take That!: The derelict and damaged starship drifting in hyperspace was recognisably derived from a licensed toy of an Eagle Transporter from rival series Space: 1999.
- Taken for Granite: Cessair's fate. Unusually as a monolith rather than a statue.
- Techno Babble: The Doctor babbles quite a lot, but Professor Rumford pulls off a lot of Archaeo Babble too.
- Too Dumb to Live: When confronted with a door which is clearly marked as 'do not open', what does the Doctor do? Exactly what the Doctor always does: Open it, of course, and get sentenced to death.
- The X of Y
- Vapour Wear: Professor Rumford wears a silk blouse without a bra when the air is a bit chilly.