The Doctor, Nyssa, Tegan and Adric land in a cave system that seems to be constantly changing around them. Consequently, they get separated when the cave starts sending them down different passages. They encounter some very bizarre people in bizarre places, such as a crashed spaceship, a regal court and a monastary. How can all of these people be here and how can they trust them if they can't even trust their environment?
This story was Matthew Waterhouse's first foray into working with Big Finish, after years of turning it down, making this his first time playing Adric as a regular since "Earthshock". This allowed for stories to be made featuring the original Fifth Doctor team for the first time in more than 30 years. To mark the occasion, this story was released in a box set, along with "The Iterations of I".
Psychodrome contains examples of:
- Action Film, Quiet Drama Scene: While preparing to deal with Magus' attack in the monastery, there are two small bonding scenes between Tegan and Adric as well as the Doctor and Nyssa.
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Angst? What Angst?: Averted. Tegan and Nyssa get to have a bit of time to mourn Tegan's Aunt Vanessa and Nyssa's home planet of Traken, unlike in the TV series where the implication of these massive events was barely mentioned at all. - Big Bad Wannabe: King Magus, once he discovers that he's based off how Nyssa views The Master, decides to live up to her expectations and quickly turns into an Omnicidal Maniac.
- Book Ends: This story takes place after the TARDIS team's first chronological story together (and after the "birth" of the Fifth Doctor) while the following story in this box set takes place just before their final story together (when Adric dies).
- Call-Back:
- Tegan reminds Adric that this Doctor is not the one Adric has spent his time recently travelling with.
- Taking place immediately following the events at Castrovalva, there are multiple references to that story, such as Tegan accusing Adric of creating the Psychodrome like he had Castrovalva.
- Call-Forward:
- Magus's last words, below.
- The Doctor suggests taking his companions to the Eye of Orion.
- When Nyssa and the Doctor are discussing the destruction of Traken, Nyssa tells him she hopes he never knows what it feels like to be alone in the universe.
- Continuity Cavalcade: Every aspect of this story is based off something from the season's setting (season 19) or the previous season with Tom Baker (season 18).
- Continuity Nod:
- Adric places Tegan in the bedroom nearest to the TARDIS console room to prevent her from getting lost in the corridors again. It used to be Romana's room, which Adric believed the Doctor had jettisoned from the TARDIS shortly before Tegan showed up. He theorises that Romana must have had more than one room.
- When Adric talks about when he joined the Doctor, he is reminded that he didn't so much "join up" as "stow away".
- King Magus taunts Nyssa with the memory of her father's death.
- Expy: Everyone who isn't part of the TARDIS crew. One aspect of the planet they're on is that it is populated by people straight from the minds of the visitors (in this case, The Doctor and his friends). Everybody on the planet is either based on each of their fellow TARDIS travelers or one of the enemies they have faced.
- Fire-Forged Friends: None of the characters at the beginning of the story can really be called friends, as at this point in time they don't really know each other yet; Tegan only stumbled aboard about a day earlier (from her perspective), and though Nyssa had met The Doctor previously and Adric has been travelling with him, his recent regeneration makes him practically a stranger to them all. This story puts them into a dangerous situation where they all have to open up to and rely on each other, and they come out of the experience much closer (though Tegan still wants to go home).
- Flanderisation: Inverted. The supporting characters are based on the main character's first impressions of each other, since the TARDIS team don't know each other well enough at this point to develop more nuanced characters.
- Foreshadowing: Two instances for Adric, including his unfailing faith in the Doctor, even as he claims, it could lead him to his death as long as people are saved, as well as his fear of encountering a very difficult maths equation both foreshadow his death in Earthshock.
- Genius Loci: The Psychodrome, capable of reading the minds of any visitors and creating people and environments based on what it finds there.
- Immediate Sequel: This story picks up directly after Castrovalva, with Adric showing Tegan to her new bedroom after they've gotten back aboard the TARDIS at the end of that story.
- It Will Never Catch On: This story features the first chronological appearance of the Doctor saying "brave heart" to Tegan. She thinks it's silly and not at all comforting and tells him not to say it again. He clearly didn't listen.
- Last of His Kind: After not having a moment to breathe after the madcap events of "Logopolis" and "Castrovalva", Nyssa finally gets to take a few minutes to realise and accept the fact that she is the only Trakenite left after the destruction of her home planet.
- Nice Job Breaking It, Hero: Like the following story, the Arc Villain of this story only became one because the Doctor and Adric couldn't shut up about the baddie's potential for receiving more power. In this case, blurting out the reveal that everyone is made up from the heroes imaginations, and Magus is based partially on The Master.
- Only Sane Man: Tegan certainly views herself this way and, given the crazy caricatures encountered in this story, she's not exactly wrong.Tegan: Don't mind me! I'm just the voice of sanity.
- Sequel: This is Castrovalva up to eleven. Having just escaped from there, many comparisons are made between both places.
- Sesquipedalian Loquaciousness: Professor Rickett is a cowardly fop who tries to cover up his inadequacies by speaking like this constantly. The Doctor is particularly irked by this, as Rickett is a personification of the way that Tegan sees him.
- Shout-Out:
- Tegan compares Magus' Castle to "Castle Frankenstein".
- She also scathingly refers to Queen Antigone as "the Queen of Hearts".
- Tempting Fate: Reunited with his new friends in the TARDIS, the Doctor as always, pokes at fate with a very sharp stick.The Doctor: What Could Possibly Go Wrong? note
- Then Let Me Be Evil: The King decides that if he's based off an evil person, he'll be evil too, no questions asked.
- Undying Loyalty: Despite Nyssa and Tegan having only just joined the TARDIS and Adric not really knowing the new Doctor, the three of them have already learned enough to know they can trust him with their lives. This trust in him ends up defeating the Magus and saving the day.
- "What Do They Fear?" Episode: The Psychodrome itself attempts to invoke this on our heroes. They are:
- For the Doctor, the loss of faith from his closest friends.
- For Adric (the mathematician), a mathematical equation he can't solve, as well as spiders.
- For Nyssa (the biologist), a plague she can't cure and not being able to save the people closest to her, like her home planet.
- Tegan was deeply afraid of some Aboriginal caves as a child, believing the paintings were monsters coming to life, which is used against her here.
