Immortality: sounds great until you realize it comes with a lifetime subscription to space leprosy.
Short Synopsis
The Doctor, Nyssa, and Tegan bump into a new companion candidate, Turlough — a schoolboy who is secretly plotting the Doctor’s murder. Meanwhile, the Brigadier is living his best retired-teacher life until a timey-wimey accident drags him into a paradox. Add in Mawdryn and his band of mutant immortals, who want the Doctor’s regenerations to cure their “can’t die, can’t live” curse, and you’ve got a story full of guilt, time loops, and bad perms.
Extended Storyline
We begin at a British boys’ school in the 1980s, where Alastair “Old Soldier, New Hobby” Brigadier Lethbridge-Stewart is now working as a math teacher. He’s retired from UNIT, traded alien invasions for grading algebra, and is blissfully unaware that the universe is about to dump a mess right on his cricket pitch.
Enter Turlough — a smug, ginger student who immediately screams “future companion” and “cannot be trusted” in equal measure. Sure enough, he’s contacted by the Black Guardian, who looks like a villainous birdwatcher with a crow strapped to his head. The Guardian offers Turlough freedom from his boring school life in exchange for one tiny favor: murder the Doctor. Turlough, being pragmatic (and deeply shifty), says, “Sure, why not?”
Meanwhile, the Doctor, Nyssa, and Tegan attempt to land in 1980s England but end up trapped in orbit on a derelict spaceship. Inside, they discover a band of rather unfortunate-looking humanoids who appear to have lost a fight with a glue gun and some silver bubble wrap. Their leader, Mawdryn, explains their tragic backstory: they stole Gallifreyan tech, tried to make themselves immortal, and got it spectacularly wrong. Now they’re stuck in a state of eternal half-life — can’t die, can’t regenerate, just shuffle around the ship looking like zombie extras on strike. Their only way out? Drain the Doctor’s remaining regenerations.
Meanwhile (because this story LOVES a meanwhile), the Brigadier gets caught in a temporal paradox. There are twoBrigadiers: one from 1977, fresh out of his UNIT days, and one from 1983, trying to enjoy a peaceful retirement. Naturally, the Doctor warns that if the two versions ever meet… kaboom. Reality implodes. Which means, of course, they’re destined to bump into each other.
Turlough, still under orders from the Black Guardian, sabotages things here and there but fails to properly assassinate the Doctor. To his credit, he does manage a few good sulks and a suspicious amount of lurking. Nyssa, as usual, handles everything with grace, though Tegan spends most of her time shooting suspicious looks at Turlough like she can already sense his “dodgy traitor energy.”
As the plot barrels forward, Mawdryn makes his case: he and his fellow bubble-wrap mutants need the Doctor’s regenerations to finally rest in peace. The Doctor, understandably reluctant to throw away all his future lives for someone else’s mess, hesitates. But in a rare show of self-sacrifice, he actually considers doing it, because the Doctor’s moral compass occasionally swings toward “martyrdom.”
The climax builds as the two Brigadiers inevitably come face to face, triggering a temporal discharge that provides just enough energy to end Mawdryn and his people’s cursed existence. They finally get the death they’ve been longing for, which sounds bleak but actually counts as a happy ending in Doctor Who. The Doctor keeps his regenerations intact, the Brigadier survives, and Turlough… somehow ends up joining the TARDIS crew despite the whole “tried to kill you” thing. (The Doctor’s background checks for new companions remain nonexistent.)