History Recap / BigFinishDoctorWho197TheEntropyPlague

** Nyssa brings up the last time they encountered entropic energy in [[Recap/DoctorWhoS18E7Logopolis "Logopolis"]], when it destroyed her home planet and vaporized The Monitor.

** The crank handle the Doctor uses to open the TARDIS doors when it [[Recap/DoctorWhoS11E3DeathToTheDaleks loses power]] is mentioned.

** The crank handle The Doctor uses to open the TARDIS doors when it [[Recap/DoctorWhoS11E3DeathToTheDaleks loses power]] is mentioned.

* GetOut: [[spoiler:Adric]] says this to The Doctor, being understandably furious with him for [[spoiler:not stopping Nyssa's self-sacrifice.]]
* GrandFinale: [[spoiler:For the reunited team of The Doctor, Tegan, Turlough and the older Nyssa, which began in [[Recap/BigFinishDoctorWho136Cobwebs "Cobwebs"]], five real world years and fourteen stories ago.]]

* InMediasRes: The story begins with The Doctor [[spoiler:arriving at Adric Traken's home to tell him that his mother won't be coming back]], before he (and Tegan and Turlough) go back to the beginning and explain.
* LaymansTerms: Thoroughly exhausted with the whole story towards the end, Tegan demands that The Doctor do his exposition of the latest inter-dimensional crisis in words of one syllable.

* PragmaticHero: Turlough in spades, and this is the first time that his different outlook clashes enough with [[AllLovingHero The Doctor's]] to cause an argument between them. While Nyssa and The Doctor argue about which of the two of them should sacrifice themselves to save everybody, Turlough wants to offer up one of the pirates instead, firmly believing that the good The Doctor and the TARDIS crew do for the universe makes them more deserving of living than the murderous, evil pirates. The Doctor is furious that Turlough could have spent so long travelling with him without learning to see things his way, while Turlough is frustrated that The Doctor's first solution is always to sacrifice his own life instead of trying to TakeAThirdOption.

* TeethClenchedTeamwork: Briefly between The Doctor and Captain Branarack. Tegan is particularly outraged, since Branarack had recently tried to ''sacrifice her''.

* BittersweetEnding: The TARDIS crew escape E-Space, which is also saved, but at the cost of Nyssa remaining trapped there without any hope of return, never able to see her children again.
* BookEnds: [[Recap/DoctorWhoS18E6TheKeeperOfTraken The first time]] we ever see Nyssa is as a young woman, tending the groves in her home on Traken. This is chronologically her final story, and she spends her elder years retiring from adventuring and medical care to look after her own gardens in E-Space.

* ForegoneConclusion: Since Nyssa never reappeared on the television series after "Terminus", her departure was inevitable.
* GetOut: Adric says this to The Doctor, being understandably furious with him for not stopping Nyssa's self-sacrifice.
* GrandFinale: For the reunited team of The Doctor, Tegan, Turlough and the older Nyssa, which began in [[Recap/BigFinishDoctorWho136Cobwebs "Cobwebs"]], five real world years and fourteen stories ago.
* HeroicSacrifice: Exactly who gets to make one and when they get to do it is the subject of much debate throughout the story. Ultimately, Nyssa gives up her youth and her only chance of returning to her family to power the portal that will get her friends home.
* IChooseToStay: Nyssa, for the [[Recap/DoctorWhoS20E4Terminus second time]].
* InMediasRes: The story begins with The Doctor arriving at Adric Traken's home to tell him that his mother won't be coming back, before he (and Tegan and Turlough) go back to the beginning and explain.

* MaybeEverAfter: Even though Nyssa closes the CVE, saving her friends and preventing the immediate destruction of E-Space, it still only has a few centuries left before entropy consumes it again, not long at all in universal terms. The apparent birth of a new star near the end of Nyssa's life, however, could mean that there is a chance life could continue to flourish there.

* SenselessSacrifice: Poor Cherryane straps herself into Pallister's machine and has her youth painfully drained from her, and it doesn't buy the others even a full minute of escape time.

* TheStarsAreGoingOut: Happening all over E-Space as a result of entropy dramatically shortening the universe's lifespan. At the end, a new star seems to appear, so all might not be quite as dire as it appears.

* TrappedInAnotherWorld: Nyssa lives out her final years on the planet Apollyon in E-Space, having given up her only chance of getting home to allow her friends to do so.

* YouCantGoHomeAgain: As had been hinted at in "Prisoners of Fate", here Nyssa is prevented from ever getting back to her own universe or seeing her family again, remaining in E-Space for the rest of her life.

* TearJerker: Nyssa's emotional farewell letter to her family as well as to her friends definitely tugs at the heart strings.

* TheWoobie: Poor Cherryanne. She lost her parents, her brother is sick with the Entropy Plague and later dies of it, becoming a Sandman monster. She is kidnapped, nearly sacrificed, terrified out of her wits, and when she gets up the courage to make a HeroicSacrifice to let the TARDIS team escape, her life force ends up not being strong enough to even give the others time to take off, throwing away her youth in a SenselessSacrifice instead.

* BeCarefulWhatYouWishFor: The SpacePirates sought to find and kidnap someone to power the portal, someone strong-willed and with "fighting spirit". They kidnap [[TheSnarkKnight Tegan]], who threatens to "put her fighting spirit right where it hurts". The Doctor comments that he's not sure who he feels more sorry for.

* ForegoneConclusion: Since Nyssa never reappeared on the television series after her "Terminus", her departure was inevitable.

* TheWoobie: Poor Cherryanne. She lost her parents, her brother is sick with the Entropy Plague and later dies of it, becoming a Sandman monster. She is kidnapped, nearly sacrificed, terrified out of her wits, and when she gets up the courage to make a HeroicSacrifice to let the TARDIS team, her life force ends up not being strong enough to even give the others time to take off, throwing away her youth in a SenselessSacrifice instead.

* TheVirus: The titular Entropy Plague. It rapidly ages everything it comes into contact with and, at the point of death, transforms them into the Sandmen, zombie-like monsters who can kill others with a touch.

* PragmaticHero: Turlough in spades, and this is the first time that his different outlook really clashes with [[AllLovingHero The Doctor's]]. While Nyssa and The Doctor argue about which of the two of them should sacrifice themselves to save everybody, Turlough wants to offer up one of the pirates instead, firmly believing that the good The Doctor and the TARDIS crew do makes them more deserving of living than the murdering pirates. The Doctor is furious that Turlough could have spent so long travelling with him and learned nothing, while Turlough is frustrated that The Doctor's first solution is always to sacrifice his own life instead of trying to TakeAThirdOption.

* InMediaRes: The story begins with The Doctor arriving at Adric Traken's home to tell him that his mother won't be coming back, before he (and Tegan and Turlough) go back to the beginning and explain.