[[caption-width-right:350: Sarah... ... ...that's not how you wear a ri- [[BreakingTheFourthWall GAH]] [[EyeScream MY EYES!]]]]
->''"I must be mad. I'm sick of being cold and wet and hypnotised left, right and centre. I'm sick of being shot at, savaged by bug eyed monsters, never knowing if I'm coming or going... or been... I want a bath, I want my hair washed, I just want to feel human again... and, boy, am I sick of that sonic screwdriver. I'm going to pack my goodies and I'm going home..."''
-->-- '''Sarah Jane Smith'''
Arriving back in modern-day England, the TARDIS lands in an actual quarry for a change. The Doctor thinks it's all very nice that there's a big siren to welcome them and a guy way in the distance seems to be happily waving at them. The quarry, of course, immediately explodes in a routine procedure, and Sarah Jane is buried under the rubble.
Before being rescued, Sarah touches what seems to be a fossilized hand and is taken over by the spirit of Eldrad, a Kastrian criminal punished by disintegration -- but whose hand has survived, and whose spirit lives on inside the ring on its finger. Sarah takes the ring and goes to a nearby nuclear research station, with the Doctor and friends arriving a few minutes later. She uses the energy to recreate Eldrad's body, absorbing all available nuclear energy. The Doctor and the resident lead scientist, Dr. Watson, convince the RAF to bomb the place (after evacuating everyone). Eldrad isn't bothering, and appears in the form of a very beautiful, very confused woman. When she learns that hundreds of millions of years have passed since she crash-landed on Earth, she asks the Doctor to take her back in time, but he refuses. He does, however, agree to take her home to Kastria in the present. But when they arrive, there is only a dead planet and a mocking message from the last king of the Kastrians. Eldrad (now in a male body) is furious, turns out to be evil after all, and forces the Doctor to take him back to Earth so that he can rule there instead. The Doctor and Sarah trip Eldrad using the Doctor's scarf and the crystalline being falls into a crevasse and shatters.
Returning to the TARDIS, the Doctor is summoned to Gallifrey and, as he thinks that he can't take Sarah with him, he gives her a lift home to South Croydon. She was planning on leaving anyway, so although the farewell is bittersweet, she doesn't mind too much... only for her to realise, as he departs, that she doesn't recognise the street where he's left her. And that it's probably not even South Croydon. (As we find out [[Recap/DoctorWhoS28E3SchoolReunion much later]], it was, in fact... Aberdeen.)
* BBCQuarry: Played with, as the TARDIS lands in... an ''actual'' quarry.
* BizarreAlienBiology: Inverted. Sarah Jane is able to shake off the effects of a poison gas, because it is designed to be deadly to [[SiliconBasedLife silicon-based]] Kastrians.
* BrainwashedAndCrazy: ''Eldrad must live!''
* DisneyVillainDeath: Eldrad.
** Before him, the nuclear reactor worker that tried to kill the Doctor, though he wasn't really a villain.
* TheDulcineaEffect: The Doctor seems a lot more willing to help Eldrad when s/he looks like a [[http://static.tvtropes.org/pmwiki/pub/images/sexybluechick_2266.jpg sexy blue chick]] rather than a [[http://static.tvtropes.org/pmwiki/pub/images/hulkingrockdude_5825.jpg hulking rock dude]]. Sarah Jane is rightly skeptical of Eldrad the whole time. Meanwhile, Eldrad was [[AFormYouAreComfortableWith actually exploiting]] this trope.
* EvilIsHammy: The more Eldrad reveals his megalomania, the hammier he gets.
* EvilSoundsDeep: Eldrad's Kastrian form.
* FatalFamilyPhoto: Fatal "last conversation with the wife and kids", anyway. Subverted when the Professor is saved at the last second rather than being killed off.
* GhostPlanet: Kastria.
* GlowingEyesOfDoom: Eldrad.
-->'''Doctor:''' "Sarah, I want you to look into my eyes."
-->'''Sarah:''' "OH NO, NO THAT'S NOT F__" ''(falls into trance)''
* ILoveNuclearPower: Eldrad can use radiation to regenerate a body! That's a useful trick.
* InsultFriendlyFire: When Eldrad explains he chose his first form to match the 'primitives', the Doctor remarks that Sarah was the first 'primitive' Eldrad met. Sarah kindly reminds him she doesn't like to be called primitive.
* IWasJustJoking: But you [[MyGodYouAreSerious gotta go home]] anyway, Sarah.
* LargeHam: Eldrad, after returning to his true form, starts to [[ChewingTheScenery devour the scenery]]. This seems to be a trait among most Kastrians -- the few others we see [[NoIndoorVoice do a lot of shouting]].
* MeaninglessVillainVictory: Eldrad returns to Kastria to become its ruler, only to find the planet entirely dead. A final message from King Rokon (the king who Eldrad planned to usurp) crowns him "King of Nothing".
* MindControl: Eldrad's hand can control anyone who's come into contact with it.
* MurderTropes: Four and Sarah have absolutely no problem with killing Eldrad.
* NuclearOption: Eldrad's taking over the nuclear reactor is considered dangerous enough to nuke it.
* PutOnABus: Sarah Jane, who returned in 1983 for [[Recap/DoctorWho20thASTheFiveDoctors "The Five Doctors"]].
* SequelHook: The call from Gallifrey leads directly into the next episode.
* SiliconBasedLife: The Kastrian race.
* StunGuns: Eldrad's ring can knock out people for a time ranging from a few seconds to about an hour.
* UltimateDefenceOfTheRealm: The RAF try to destroy the nuclear power station and Eldrad with a nuke. It doesn't work.
* WomenAreWiser: A villainous example. Eldrad is in fact evil, but the female version is much more thoughtful and calculating, while the male version is a blustering moron who gets himself killed by tripping over a scarf.