The one with BRIAN BLESSED.
The trial continues, and the Valeyard decides to bring out another piece of evidence against the Doctor: his antics on the planet of Thoros Beta.
The footage shown to go along with the trial has the Doctor and Peri landing on the aforementioned Thoros Beta, a planet beach with green sky, blue rocks and a pink ocean. They meander around the beach before going into a cave - and are quickly captured by natives of the planet. Among those aliens is Sil, whom the Doctor suspects is behind the problems of this planet as well. As it turns out, this is Sil's homeworld, the planet of his species: the Mentors. The Doctor and Peri are taken to a Doctor Crozier and his experiments — one of them being the ever-lovable BRI... King Yrcanos. Before the Doctor can object, a lie detector is slapped on his head and the Mentors begin to probe his mind. Before it can do much, however, Yrcanos blows up the machine, breaking free and taking the Doctor and Peri with him. Yrcanos plans to go steal weaponry and blow up the Mentors, but the Doctor then whacks the king on the head and turns Yrcanos and Peri over to the Mentors.
As it turns out, the Mentors are being evolved into higher beings by Doctor Crosier — and the leader Kiv now needs a new body before his brain essentially explodes. Trying to avoid himself becoming a target of that transplant, the Doctor interrogates Peri and accuses her of being against the Mentors repeatedly. Meanwhile, the Doctor is denying that this happened at all during the trial — and that he's being manipulated by someone who's messing with the Matrix (again, not that one). Finally, Yrcanos escapes with Peri and both join the resistance against the Mentors — and plan a massive attack against the Mentors as well, but are stunned and captured. Sil and Crozier decide to use Peri as a more suitable body for Kiv's brain, despite the Doctor's objections. As the operation is being prepared, the Doctor sneaks away and frees Yrcanos, urging him on for Peri's safety.
Peri is strapped down and gagged as the operation is prepared. As the Doctor and Yrcanos run to go save her, the Time Lords intervene and rip the Doctor out of time... and then purposely delay Yrcanos' strike force from actually freeing Peri until after the experiment is over with, directly playing a role in her death. As you can guess, the Doctor (finally remembering the events of this story, piece by piece) is not pleased with this at all.
Time slowly resumes its normal course and all that's left of Peri is Kiv. Yrcanos, having fallen for her over the course of the story, is devastated and blows everything up — whatever remains of Peri included. The Doctor, watching this from the courtroom, is shocked into silence. The Inquisitor and the Valeyard tell him that it was necessary to end Peri's life to prevent the disastrous consequences of Crozier's experiment, and the Valeyard further claims that Peri's death is ultimately the Doctor's fault as he abandoned her in the first place. But rather than numbly accept the accusations of the Valeyard, however, the Doctor angrily insists that there is something extremely fishy about this whole trial and that he was removed from time for other, more sinister reasons. He vows to get to the bottom of all this, and that he will somehow avenge the loss of Peri.
This serial is notable for featuring venerated actor BRIAN BLESSED in a major role as King Yrcanos. This serial is more notable among the fans, though, for having a companion killed off rather than given a happy ending... at least until John Nathan-Turner's cold feet reversed it at the end of the season.
- Alien Sea and Alien Sky: Thoros Beta has a green sky (with another planet visible, large and close enough to see its rings) and a pink ocean.
- Author Appeal: The concept of the Mentors being a heavily-capitalist society, buying up planets and then using them up is a self-admitted example from author Philip Martin. No one really cares, though, because the whole effect of the species is just that cool - especially for the 1980s.
- The Bad Guy Wins: Although it gets reversed in the end, Peri's death ends up casting the Doctor in an even worse light than before.
- Bald Women: Peri, after the surgery placing Kiv's brain in her body.
- Bastard Understudy: Sil to Kiv, technically... though Kiv seems to have slowly lost it as the story progressed.
- Batman Gambit: Frax pulls a villainous one; he knows the resistance aren't really fighters, and are therefore likely to just hide out in the caves for a long time. But he also knows that Yrcanos is suicidally brave and will rally them to attack, so when he escapes all Frax has to do is sit back and be ready for them.
- Big "NO!": King Yrcanos (BRIAN BLESSED!), who else?
- Bound and Gagged: Happens to Peri when Doctor Crozier decides to experiment on her.
- Crapsack World: Thoros Beta.
- Disney Death: The Doctor is shown a scene in which Peri, her mind hijacked by Kiv, is apparently killed. However, it is later revealed that the scene in question had been fabricated and Peri is "alive and well and living as a queen".
- Distressed Dude: Damn, Yrcanos just can't stay free.
- Dropped a Bridge on Him: Subverted; Peri's character's death was overturned in "The Ultimate Foe".
- Evil Is Hammy: King Yrcanos, which is no surprise since he's played by BRIAN BLESSED! However, he only really has that status at the start of the story — The evil, that is. Not the hamminess. In fact, the hamminess just keeps increasing as the story progressed.
- Expy: Ycranos is not dissimilar to BRIAN BLESSED's Prince Vultan.
- Grand Theft Me: Poor, poor Peri.
- Ham-to-Ham Combat:
- Heroic BSoD: Played straight with the Doctor at the end of the serial. Subverted with King Yrcanos, as he suffers from one... but that ends with the typical results of a Villainous Breakdown instead.
- Hot-Blooded: Ycranos, of course.
- Mad Doctor: Crozier.
- Mind Rape: Peri is subjected to one by Sil, in a very traumatic and disturbing way with a lot of blatant rape subtext. It includes a Traumatic Haircut and she's considered technically dead after it.
- Mind Screw: Exactly how "real" the events of this story are is never stated.
- No Indoor Voice: In addition to the Sixth Doctor, we have King Yrcanos. It's amazing that anyone's hearing was left intact.
- Noodle Incident: The adventure that brought Peri and The Doctor to Thoros Beta in the first place. It involved a Warlord of Thordon gifting a powerful weapon to The Doctor with his dying breath, and the "dirty old warlord" apparently took quite an unsavory liking to poor Peri.
- La Résistance: Yrcanos and his merry men.
- Plot Hole: The Doctor's behavior during the flashback footage after Yrcanos frees him from the mind-machine. Supposedly, the Doctor was supposed to be blended with Yrcanos' personality — but a serious communications problem prevented Colin Baker from getting this important piece of information. As such, the Doctor comes off as a royal jerkass. Baker explains the script problem in this interview.Colin Baker: He said "I don't know, you'd better ask Philip Martin", so I got in touch and gave him those three alternatives, he said "I don't know, Eric wrote the trial stuff, all the Matrix stuff was added after, by Eric, you'd better ask him." So I went to John Nathan-Turner, he said "Oh, whichever you like."
- The production subtitles on the DVD release include a quote from Nathan-Turner, where he claimed he believed the Doctor being out of character was the result of the Valeyard tampering with the evidence.
- Prefers Raw Meat: Sil's favourite snack is marsh minnows: a kind of newt mostly eaten alive.
- Proud Warrior Race Guy: King Yrcanos is slightly ludicrous in his constant blustering but mostly on the side of right. But that's only because the story has a major case of Crapsack World and Evil vs. Evil: in many more optimistic Doctor Who stories, Yrcanos would have been a bloodthirsty villain by comparison to nicer characters.
- Royals Who Actually Do Something: Kin Yrcanos is a classic Warrior King.
- Screaming Warrior: Yrcanos continues to shout and scream even when not actually fighting.
- Sequel Episode: Sil's return makes this a sequel to "Vengeance on Varos". There were plans to bring him back anyway in the original series 23 for "The Ultimate Evil", where he'd partner with the Ice Warriors.
- Shout-Out: When first in Crozier's lab, the Doctor examines a chestburster in a glass tube.
- Special Effects Beef Up: Just... damn. The scenery has been turned into something fantastic with just a subtle application of a retro software known as Quantel Paintbox. Think of it as a 1980's Photoshop for film.
- Stuffed into the Fridge: Peri, the first time a female companion had been killed off since "The Daleks Master Plan". After an entire tenure of being objectified and abused in a kinky sort of way by every villain, she gets a Traumatic Haircut, a Mind Rape and is murdered, her brain is physically removed and replaced with Sil's. Then her possessed body is killed by Yrcanos who had fallen in love with her. She gets better. Probably.
- Take That!: Peri tells Ycranos about Earth:Oh, you'd like it there. Lots of madmen playing at warriors and actors playing over the top in politics.
- Unreliable Narrator: The Matrix itself, here, although to exactly what degree the events have been falsified is never made clear.
- Visible Boom Mic: After the Raak has finished attacking the Doctor and Peri and dies, a boom shadow can be seen across Colin Baker's head.
- Warrior Heaven: King Yrcanos describes one of these. Peri does no seem impressed.
- Was Once a Man: The Lukoser. Now he's a sort of horrifying mutant man-wolf hybrid, though his mind is still clear enough to fight for Yrcanos.
- What the Hell, Hero?:
- The Doctor is called on his Moral Dissonance behavior by Peri, who is just as confused as the audience as to what the hell is going on.
- The Doctor also calls out the Time Lords on their intervention in Peri's rescue.
- World of Ham: Perhaps one of the hammiest productions Doctor Who has ever done.