[[quoteright:350:http://static.tvtropes.org/pmwiki/pub/images/Ogri_4473.jpg]]
[[caption-width-right:344: [[Recap/DoctorWhoS17E1DestinyOfTheDaleks "Oh look, rocks!"]]]]

->'''Professor Rumford:''' ''Are you from outer space?''
->'''The Doctor:''' ''No, I'm more from what you'd call "inner time".''

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 [[HomoeroticSubtext 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 BotheringByTheBook. He manages to knock Fay unconscious by poking her necklace, 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.

!!Tropes

* AIIsACrapshoot: The Doctor's tale of justice machines.
* AllMythsAreTrue
* AncientAstronauts
* AndIMustScream: Cessair's fate.
* ArtShift: Fourth and final Tom Baker episode shot entirely on video. The show would ditch film for good at the start of "[[Recap/DoctorWhoS23E1TheMysteriousPlanet Trial of a Timelord]]".
* BeatThemAtTheirOwnGame: How the Doctor outwits the Megara.
* BotheringByTheBook: Four once again shows his expertise at this.
* CallBack: The spaceship has a dead Wirrn in it.
* CelticMythology
* CoolOldLady: 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.
* CutenessProximity: The Doctor's insistence on treating K-9 like an actual dog is quickly taken up by Amelia as well.
* EverythingsBetterWithSparkles: The Megara are pretty much just sentient sparkles.
* ExpositionOfImmortality: There are three portraits missing from the wall at Boscombe Hall. The Doctor and Profesor Rumford come across them later, revealing them to all be portraits of Vivien Fay painted at various points during her long existence on Earth.
* FailedASpotCheck: Everyone gets ambushed several times over by ''eight foot tall moving rocks''.
* {{Golem}}: The Ogri are a mix of this and LivingStatue, since they're part of a stone circle.
* HalfwayPlotSwitch: In which a story about Druids and human sacrifice in a stone circle suddenly turns into a courtroom drama aboard a hyperspace ship.
* HomoeroticSubtext: 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..."
* IHaveManyNames: Cessair, aka Vivien Fay, aka Morgana Le Fay, aka The Goddess, aka The Cailleach... need we go on?
* JudgeJuryAndExecutioner: The Megara.
* LiteralCliffhanger
* MilestoneCelebration: Averted. This is the 100th [[Series/DoctorWho Doctor Who]] serial '''and''' its original broadcast was close to the series' 15th anniversary. There would have been a scene in which the Doctor would have gotten a cake and a new scarf for ''his'' birthday, but the idea was scrapped because it was considered to be too self-indulgent.
* MoodWhiplash: The serial goes from a dark, gruesome horror story to... a black comedy about malfunctioning justice robots. [[JustifiedTrope Could be justified]] in that the show's had far too many tonal shifts for just one tone to be represented by the 100th story.
* OurOgresAreHungrier: The Doctor suggests that Gog, Magog, and Ogre could be inspired by the Ogri, large rocks that feed on blood.
* PlotAllergy: Cessair, like all Diplosians, has an aversion to citric acid, which helps in discovering her true identity.
* Really700YearsOld: Vivien Fay has been on earth for 4000 years.
* SealedEvilInACan: A slight variation happened, where the Doctor releases a pair of biomechanical judges called the Megara from a ship stranded in hyperspace, [[spoiler:and the judges promptly sentence him to death for letting them free without the proper legal authorization.]]
* SiliconBasedLife: The Ogri.
* StrippedToTheBone: The Ogri can do this to anyone who touches them.
* TheXOfY
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