Jeremy Dyson (played by Michael Sheen) proposes to the other members of The League of Gentlemen a bold new series in which everyone in Royston Vasey wakes up with a tail. The idea excites the writers who want to push forward, but they are quickly confronted by three familiar figures from their world—Papa Lazarou, Edward, and Tubbs—and the confrontation ends badly when the creator tries to escape but plunges off a cliff.
The drama intensifies at a church where the vicar, Bernice Woodall, warns Pauline Campbell-Jones and Mr. Chinnery that signs of The Apocalypse are appearing. In a parallel nightmare, Hilary Briss has escaped from prison, holding Herr Lipp hostage and forcing him to hijack a car driven by Geoff Tipps. Fireballs fill the sky as Briss helms the group through a door in the church crypt, stepping into Hadfield, the real town that Royston Vasey represents in The League of Gentlemen.
With newcomers and old allies gathered, Briss, Herr Lipp, and Geoff Tipps travel to London. Lipp masquerades as his own creator and visits Steve Pemberton’s home, only to find that Pemberton has been neglecting his family. Briss and Tipps pore over The League of Gentlemen’s new project, a historical horror titled The King’s Evil, while Briss relentlessly pursues an escapee Pemberton and reclaims him. Back at their hideout, Briss discovers Tipps has woven himself into The King’s Evil as the hero, and Lipp develops a troubling attachment to Pemberton’s family, rifling through his belongings for his notes.
Briss escorts Pemberton back to Hadfield, where a tense phone call to Reece Shearsmith leads to a mistaken belief of a prank. When Shearsmith and Gatiss discover the ruse and capture Herr Lipp, they travel to Hadfield and then return to Royston Vasey through a dimensional door, swapping hostages. The plan crumbles when a stray gunshot kills Pemberton. Dr Erasmus Pea—the villain from The King’s Evil—tries to lure Briss away from Royston Vasey and ends up turning his fellow characters into a gigantic homunculus. Briss fights the monstrous creation, while Shearsmith and Gatiss climb the church walls to escape; tragically, Shearsmith falls to his death.
Briss finally kills the homunculus, but Pea fatally wounds him from behind. Before dying, Briss tells Tipps that he is the only one who can save Royston Vasey. Tipps battles Pea while Gatiss struggles to return to the real world but is held at gunpoint by Lipp. Tipps defeats Pea by using a portion of the homunculus, and the tension in the church escalates as Lipp threatens Gatiss. The others urge him to reconsider, explaining that without the writers Royston Vasey would cease to exist and everyone would die. Tipps persuades Lipp to yield the gun, insisting that Lipp can still choose to change, but a stray shot fires and kills Gatiss instead.
With all the writers now seemingly dead, the town braces for the worst. Instead, a startling calm settles over Royston Vasey, and the Apocalypse appears to be averted. The residents discover they now have free will: Herr Lipp adopts some orphaned children, the vet Mr. Chinnery finds a rabbit he can care for without harm, and Bernice and Pauline grow closer and become romantically involved. Tipps leaves the church, bidding farewell to Edward, Tubbs, and Papa Lazarou. Royston Vasey seems poised to continue on its own terms, independent of its dead creators. In a mid-credits scene, Dyson is revealed to be alive but in a coma after the fall, and everyone else in the world finally discovers they now have tails.
