The Tenth Doctor and Donna respond to hundreds of distress calls coming from the planet Death's Deal. They're too late. In fact, they're so too late that a tourism industry has grown up around looking at the wreckage. They're quick tours though, because all the wildlife on Death's Deal is exceptionally unpleasant, and it's really not a good idea to stick around.

So naturally, the tour ship gets trashed and the TARDIS gets swallowed by a monster. That's when two of the tourists turn out to be pirates, Groogan and his not-girlfriend Lyric, looking for treasure. Together with the Doctor and Donna, and a molluscoid anthropologist called Krux, they set on a quest across the most deadly planet in the galaxy. And the Doctor's picked up another message. It just says "Alons-y!"

When they get to the treasure ship, there's no treasure, just Eleventh's message telling Tenth that he needs to save Erskine, and that the planet is full of Slaughter crystals. Donna and Krusk get seperated from the others, and have an adventure through the underground of the planet while the Doctor discovers that Erskine is a) the surveyor who wanted to declare the planet a site of environmental interest and was shot down by an evil mining corporation b) completely mad, calling himself Father of Paradise and sacrificing subsequent crash victims to the planet's nature gods, and c) Lyric's dad, and she was only hanging around with Groogan to try to find him. He also realises that slaughter crystals are an insanely powerful weapon, that the wildlife is being driven into a frenzy by the electromagnetic radation from all the distress calls, and that the evil mining cartel have been informed about the crystals and are on their way. Now he just has to deal with being sacrificed by Erskine.

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* AssholeVictim: The disaster tourists. Especially Rude Woman Who's Actually Working For The Mining Corporation.
* AnalogyBackfire: Donna does this to ''herself''. When she's hurtling through an alien worm's digestive tract, protected by the shell of an alien mollusc, she tries to convince herself it's like the time she went zorbing. She hated zorbing.
* BBCQuarry: The original landing site is one.
* TheBigGuy: Krux is an 8 foot tall, barnacle like humanoid with several tentacles instead of hands. And he's ''huge''.
* BigWhat: Starting from a FlatWhat, as per the Doctor.
* BioluminescenceIsCool: See also BizarreAlienBiology.
* BizarreAlienBiology: Krusk has luminous tentacles that are part of his mating ritual, and can open up his shell and let Donna hide inside.
* BrokenBridge: Minutes into the story, a gigantic creature eats the TARDIS, trapping the Doctor and Donna on Death's Deal.
* CatchPhrase: The Doctor gets an "I'm sorry. I'm so sorry" and an "Alons-y!". The latter is also used by Eleventh as SomethingOnlyTheyWouldSay.
* CallBack:
** The Doctor mentions having a friend who was a shapeshifter ([[Characters/DoctorWhoMagazine Frobisher]] or [[Recap/DoctorWhoS20E6TheKingsDemons Kamelion]]?) and an enemy who was a [[TheMaster Master]] of disguise.
** The Eleventh Doctor comments on not being ginger, a reference to both his and Tenth's regeneration scenes.
* DeathWorld: Death's Deal is "the most dangerous planet in the Galaxy!"
* DistressCall: Death's Deal is surrounded by them, both current and old, and the TARDIS receives them all.
* EverythingIsTryingToKillYou: The planet's wildlife have all been enraged into unstoppable killers.
* FamilyUnfriendlyDeath: Frimbs gets liquefied and eaten by a gigantic limpet.
* GiantEnemyCrab: Or at least crab-like legs. Eats a space pirate. Subverted with two crustaceans that Erskine has tamed.
* HellishCopter: Well not exactly a helicopter, but a tour boat, but it blows up in a spectacular fashion.
* IDontLikeTheSoundOfThatPlace: Death's Deal.
* IKnowYoureInThereSomewhereFight: Lyric tries this on her father. The Doctor explains that at this point, remembering he was Merrit Erskine would just be too much for him to handle.
* IWantMyMommy:
--> '''Groogan''': Mum... I want my mum..!
* MementoMacguffin: Erskine has a locket containing pictures of his wife and daughter. He never opens it, because he doesn't want to be reminded.
* NatureHero: Erskine, sort of.
* OneHitKill: One scratch from a Slaughter Crystal causes a lightning quick infection that first starts to sting, then takes away your senses and kills you under a minute.
* TheProfessor: Professor Erskin.
* SheIsNotMyGirlfriend: Lyric towards Groogan.
* SingleBiomePlanet: The whole world seems to be one vast coral reef.
* SomethingOnlyTheyWouldSay: The distress beacon from a ship called the Howling Jupiter beeps in Morse code. A-L-L-O-N-S--Y-. The Doctor deduces it must be a message for him.
* SpacePirates: Tag Groogan.
* TheTapeKnewYouWouldSayThat:
--> '''Eleventh Doctor''': Or else millions upon millions will die.
--> '''Tenth Doctor''': *through gritted teeth* But what must I do!?
--> '''Eleventh Doctor''': And I know you're now asking "What must I do!?" because I know you best of all!
* TitleDrop: Death's Deal is the name of the planet the story takes place on.
* PetMonstrosity: Two crustaceans Erskine has tamed.
* PowerCrystal: Slaughter crystals
* ProphecyTwist: Eleventh's message doesn't say ''which'' Erskine the Doctor needs to save.
* WhenSheSmiles: Lyric smiles at the end of the story, for the first time.