The Fifth Doctor and Turlough visit Brazil in 2080, decades after the Amazon has turned to desert. But not ''everyone'' in Rio is dying a slow, lingering death brought about by environmental and economic collapse. Impossibly wealthy werewolf Ileana de Santos and her invalid son are taking a luxurious private train towards their family's private compound.

The Doctor wants to find out more about what's going on, especially once he and Turlough start being stalked by the father of all werewolves, Pieter Stubbe. Ileana, looking for a protector, latches on to the Doctor and confides in him.

The wolf band quickly realises that Turlough and the Doctor aren't human, and toy with them for a bit, ignoring Ileana's pleas. Turlough is driven mad and escapes into the forest, where he meets Rosa, a teenaged native American shaman who's the last of her tribe. She carries the spiritual remains of ''the entire forest'' (trees, animals and humans) in her mind. It's driving her a bit mad, but she's willing to bear it if it means she can kill Stubbe once and for all.

When the Doctor decides to be Ileana's new protector, it leads to an AccidentalProposal and a whole lot of angry werewolves. Fortunately, Turlough is carrying Rosa's silver blade when Stubbe swallows him whole, so he's spat back out again (although just slightly traumatised). Eventually, the Doctor saves the day by simply getting Stubbe inside the TARDIS and hovering far above the Earth for a bit. Since werewolves can't live without a connection to the soil, Stubbe is made to realise that he doesn't stand a chance, and that he's an old world artifact with no place in current human society. Instead of killing Stubbe, Rosa guides his spirit into her mind and tells him to enter her spiritual forest, [[Literature/LittleRedRidingHood as long as he doesn't stray from the path]].

With Ileana's son safe, she hopes the Doctor will stay with her as her husband -- but she can't leave the Earth, and he's not at all inclined to settle down (and just a bit embarrassed by the whole ordeal).

* AccidentalProposal: The Doctor promises to be Ileana's new champion (grand heroic speech and all), not realising that it would make him her husband. He decides to roll with it when he realises it's the only way to save her.
* ApocalypticLog
* BlindIdiotTranslation: "Loups-garoux" isn't proper French. The proper spelling would be "Loup-garoux."
* CelibateHero: Five claims that women just aren't his area. Turlough rather dryly points out the existence of Susan.
** Considering the episode was written by Marc Platt, whose novels canon involves Time Lord reproducing asexually by using ''looms'', it's safe to say that NoHuggingNoKissing is firmly in place.
* CrapsackWorld: Near-future Brazil.
* DeadpanSnarker: Turlough
* DirtyCoward: Turlough, though he shows a dash of the TheSoCalledCoward when he and Rosa are surrounded by Loups-Garoux.
* EnemyWithout: Turlough is confronted with an illusion of his dark side.
* FakeAmerican; Sarah Gale, playing a native South American with a US American accent.
* FlyingCar
* GratuitousForeignLanguage: There's German, French, and Portuguese in this story.
* GreenAesop: Played completely straight.
* HistoricalDomainCharacter: Pieter Stubbe.
* HumansAreFlawed
* IllGirl: An unusual gender flip with Ileana's son, an Ill Guy.
* InvisibleToNormals: Turlough can't see the Wolf people on the Monorail, the Doctor can.
* ItsAlwaysMardiGrasInNewOrleans: They're in Brazil. Will it be Carnival season? Three guesses, first two don't count.
** JustifiedTrope seeing as they travel through time.
* LastOfHerKind: Rosa.
* LittleRedFightingHood: Rosa.
* MagicalNativeAmerican: Rosa.
* MaleGaze: Five claims he's a CelibateHero but Turlough catches him staring.
* MeaningfulName: Rosa means "red". [[StealthPun As in]] [[Literature/LittleRedRidingHood Little Red]].
* MorallyAmbiguousDoctorate: Dr. Hayashi.
* OlderThanTheyLook: The Doctor muses he's younger than he is.
* OohMeAccentsSlipping: Rosa occasionally sounds more like she's from Newcastle-upon-Tyne than Rio.
* OurWerewolvesAreDifferent
* PerceptionFilter
* PostModernMagik: All over the episode. The werewolves travel by monorail, the shaman Rosa has a wrist computer.
* SexyDiscretionShot: Turlough and Rosa get one. Rosa calls him her boyfriend after that, although Turlough denies being involved with her when the Doctor asks him about it.
* ThereIsNoKillLikeOverkill: The planned execution for Pieter Stubbe.
* TheyShouldHaveSentAPoet: Turlough's description of his home planet is gorgeous.
* WarriorPoet: Five retains his sanity by reciting ''Literature/TheRimeOfTheAncientMariner''.
* WholePlotReference: To Literature/LittleRedRidingHood, with a twist at the end -- [[it's the wolf who enters the straight path of the forest and is told never to stray]].
* [[{{Wolfman}} Wolfpeople]]
* WolvesAlwaysHowlAtTheMoon