[[quoteright:350:http://static.tvtropes.org/pmwiki/pub/images/master_leer_1246.jpg]]
[[caption-width-right:350:"So... what kind of name is 'Perpugilliam'?" "I don't know, what kind of name is 'Master'?" "...point taken..."]]
->'''The Master:''' I am the Master!
->'''Peri:''' So what? I'm Perpugilliam Brown, and I can shout just as loud as you can!

Our story begins with a group of desert dwellers on the planet Sarn. They worship a god named Logar and they have a Chosen One, named Malkon, who is declared so because of a special double-triangle symbol burned into his arm. The people of Sarn like to bicker on if their god really exists or not, and continue to do little else for the rest of the story.

In the TARDIS, the Doctor hasn't taken [[Recap/DoctorWhoS21E4ResurrectionOfTheDaleks Tegan's decision to leave]] all that well. He curses the Daleks for a bit before Turlough tells him to snap out of it. However, before either of them can get any more lines in, a random scream pierces the TARDIS control room. Why, that must be Kamelion, and he's in danger! You remember Kamelion, right? He showed up at [[Recap/DoctorWhoS20E6TheKingsDemons the tail end]] of the last season and vowed he'd be a loyal companion of the Doctor! ...And then he never bothered to show up again until this episode.

It turns out Kamelion is lying on the ground sparking as a cable stretches into a wall of the TARDIS set. But the Doctor isn't especially worried, as he just leaves the guy laying there on the ground.

Over on Earth, the same double-triangle is mysteriously found engraved on what looks like an ancient golden dumbbell on an island nation off the coast of Africa. It's found by an American archaeologist and his stepdaughter: college student Perpugilliam "Peri" Brown. Peri wants to go off on holiday to Morocco instead with some guys she's just met, but her stepfather refuses and leaves her stranded on the boat alone, because he's a terrible person. Peri, [[SarcasmMode being of completely sound mind and judgment of course]], decides to take the rather huge artifact with her as she leaps off the boat they've been traveling on and tries to swim to shore. Of course, she nearly drowns.

Luckily, the TARDIS is right nearby. Apparently, the magical alien dumbbell is sending out a {{distress call}} of some sort. Turlough just happens to see the drowning Peri and decides to save her, only to go through Peri's belongings once he gets her into the TARDIS. Smooth. Either way, Turlough finds the golden dumbbell of the ancients and is shocked by the double-triangle, as he has the exact same symbol burned onto his arm. The Doctor, for his part of this episode, was off having tea while waiting for another bit of the signal. Once he comes back, the Doctor sets off for the source of the signal -- taking everyone to the planet Sarn. The Doctor and Turlough go out to look around.

Peri is immediately jumped by Kamelion, who has now taken the shape of... Peri's... step... father. Because Kamelion, being influenced by psychic projections, has apparently picked up on some strong negative emotions Peri has towards the man. Soon enough, though, Kamelion turns into the Master instead. The robot made to be a slave to the Master is now again a slave to the Master. No one seems very surprised by this.

The Doctor and Turlough find the Sarn people and the Doctor quickly informs them that they live in an active volcano system. Not only that, but they happen to be living inside lava tubes and vent chambers. Before much more happens, though, Turlough asks about that double-triangle symbol through showing it off on his arm. They praise him as a second Chosen One, and Turlough realizes that Malkon may well be his brother. And then Peri shows up, having run out of the TARDIS to flee from the incredibly-creepy Kamelion to let Turlough know that someone called "the Master" has just shown up.

Kamelion (still looking like, and controlled by, the Master) shows up and promptly takes over the role of "the Outsider" in the local religion, which basically means he gets to run around and tell people what to do. As silly as this seems on paper, in action it just means that Anthony Ainley gets to be awesomely hammy -- throwing his arms around like a preacher on Christmas morning. The Doctor starts acting like a complete and utter asshole to Kamelion, claiming he's trying to free the distressed droid. Then the Doctor is thrown in jail.

It turns out that Sarn is an old colonization attempt by Turlough's people, and it just so happened to be a prison world. Turlough is also a criminal-by-relation, his father having fought in a war, and having ended up on the losing side. Meanwhile, Peri is taken to the Master's TARDIS by Kamelion and she's forced into moving a small box. Looking inside the Master's "control box," she quickly sees why the Master needed Kamelion... he's doll-sized. So he runs around his TARDIS while Peri tries to crush him like one would an errant cockroach.

Apparently, he [[VillainBall accidentally]] [[HoistByHisOwnPetard shot himself]] with an advanced Tissue Compression Eliminator and needs some special regenerating gasses from the planet Sarn in order to return to normal. However, the gasses are stored in the core of the planet, and the Master's dinking around has caused the place to become geologically unstable. Turlough swallows what little pride he has left and calls his people with the wreckage of a crashed spaceship, where his brother also happened to come from. They agree to send a ship to recover those who remain on the planet. Meanwhile, Peri and the Doctor try to stop the Master's super awesome plan... but not before the Doctor decides to use the regenerating gasses to heal up a few of the sick and wounded ''[[ItMakesSenseInContext by setting them on fire]].''

However, Peri and the Doctor aren't really able to stop the Master. Instead, the Doctor is just barely able to [[MercyKill short-circuit]] Kamelion, giving the robot what the Doctor calls "an electronic heart attack." Kamelion then, in what amounts to Hulk-speak, begs for the Doctor to kill him off. Using the Master's Tissue Compression Eliminator, the Doctor coolly ends Kamelion's life, reducing him to a silver action figure. Meanwhile, the Mini-Master is finally absorbing the regenerative gasses of the planet, and grows back to size...

...until the blue flames that represent the gasses turn to real flames and burn the Master to death as the Doctor stares on in DullSurprise.

With the Master supposedly dead (again), the Doctor and Turlough part ways. The war "criminals" have long since been forgiven and Turlough's exile is lifted. Peri begs to follow the Doctor along on more adventures. and he agrees, hesitantly, and welcomes her to the TARDIS.

----

!!Tropes

* AbusiveParents: While sleeping in the TARDIS, Peri has a [[BadDreams nightmare]] about her stepfather, begging him "I-I'm sorry Howard. I didn't mean it. No Howard, p-please don't leave me alone! Do-don't turn out the lights! HOWWAAAARD!".
** WordOfGod has it that she was just reliving a childhood nightmare of being afraid of the dark, inspired by the author's own kid. The Franchise/DoctorWhoExpandedUniverse, however, took those lines and ran with them, including a reveal that Peri's step father molested her as a child.
* BeachEpisode: (at least at the start) providing an excuse for high levels of FanService from Nicola Bryant and [[ShirtlessScene Mark]] [[ShowSomeLeg Strickson]]. Actor Creator/DavidTennant and producer Phil Collinson reminisce fondly about this episode in the hidden commentary on "[[Recap/DoctorWho20thASTheFiveDoctors The Five Doctors]]". Even Creator/PeterDavison's usual cover-all outfits are somewhat relaxed.
* BigLittleMan: Done as a CliffHanger reveal when it turns out the Master has accidentally shrunk himself to a small size, and has been directing the shapeshifter robot that everyone thinks is him from a control box.
* BirthmarkOfDestiny: Malkon's brand is interpreted as one of these by the people of Sarn.
* ChekhovsVolcano
* DarkAndTroubledPast: the Turlough brothers
* DeadlyGas: Inverted - the numismeton gas is healthsome and good.
* DistressCall
* DroppedABridgeOnHim
* DullSurprise: The Doctor's slack-jawed blank expression as the Master supposedly burns alive.
* FanService: This episode is pretty much the apotheosis of Creator/JohnNathanTurner's "something for the dads" policy. Although the costumes of some of the male characters are more revealing than usual, making it more equal opportunity.
* HamToHamCombat: This adventure features a particularly hammy Creator/PeterDavison taking on an even hammier Anthony Ainley. And it is ''glorious.''
** Peter Davison notes on the DVD's "making of" documentary that Ainley originally tried to underplay the role much more than he does in the finished product. However, the serial's director, Fiona Cumming was known to favour very hammy, over-the-top performances from her actors, and made Ainley turn his performance UpToEleven.
* HomeSweetHome: Turlough's motive for leaving is that he has a chance to go home, and as a hero no less.
* HotScientist: Peri's stepfather.
* [[IJustShotMarvinInTheFace I Just Shot Myself In The Face]]: strongly implied that this is at the root of the Master's problems
* LongLostSibling: Malkon
* MaleGaze: The ''very first shot'' of Peri is a long, slow pan up her bikini-clad body in close-up. Unfortunately this set a precedent for pretty much her entire tenure on the show.
* MarkOfShame: The Turlough brothers.
* TheMaster
* MercyKill
* MoralDissonance: ''Burning the Master alive''. For a guy who's supposed to be fixated on saving people, he pretty much kicks back, lets the Master burn, shrugs, and walks away.
* NoOneCouldSurviveThat:...well, unless they had JokerImmunity, anyway.
* OohMeAccentsSlipping: Nicola Bryant, again.
* PenalColony: Sarn
* PerversePuppet: Good ol' Kamelion. Good riddance to bad props.
* PurelyAestheticGlasses: They're baaaack!
* RobotBuddy: Ditto.
* SceneryPorn: Starts out like this, but after the first episode the story actually starts doing a good job of using the Lanzarote location, making the titular planet look far more convincing than it would have been if it were just filmed in a quarry.
* ThickerThanWater: Turlough is ready to kill when Malkon is hurt. The Doctor says it would do no good, whereupon Turlough reveals that they are brothers.
* WaistcoatOfStyle: The Doctor swaps his frock coat and cricket jumper for a stylish tapestry-patterned waistcoat. Well, he is on holiday after all.
* WhatTheHellHero: Yeah, the Doctor's kind of an ass to Kamelion, isn't he? Peri seems to call him out on that during the story, but the Doctor hand-waves it by claiming he's trying to ''free'' the poor distressed robot. By being a dick to it. Riiiight.
* TheXOfY