Having successfully blackmailed Clara last week, Artie and Angie weasel their way into a trip aboard the TARDIS. The Doctor takes everyone to the greatest amusement park in the galaxy – or at least to what used to be the greatest amusement park. It's long defunct and its only occupants are a Mr. Webley and his assistant Porridge, a gang of misfit soldiers sent by the Emperor to implode the planet, and a quietly gathering army of upgraded Cybermen. The children – particularly Angie – are bored and annoyed by the whole thing. Thankfully, the Cybermen abduct them and turn them into Borg-like zombies that don't say anything for most of the episode.
The Doctor soon discovers the Cyberiad's plot, but becomes infected with the Cyberplanner's intellect. The Cyberplanner takes up residence in the Doctor's brain, where it causes him to flail and mug and argue with himself with spastic glee. It renames itself Mr. Clever. The Doctor fights to retain control of half his brain and challenges Clever to a chess match. At stake is the fate of the planet, but of course Mr. Clever has no intention of playing fairly, and the Doctor knows it.
Meanwhile, Clara is left in charge of the soldiers, who are so astoundingly incompetent that even someone with zero militaristic experience seems like a step up. Her main goal is to keep them from imploding the planet with a voice-activated bomb, which should be easy considering the only person with the voice code dies fairly early on. Of course, there comes a moment when they want to implode the planet and now no longer have that ability.
The Doctor wins his chess match with a lot of talking and a bit of trickery, and frees Artie and Angie from their silent imprisonment. Damn it. The moment Angie is free, she Wesley Crushers her way into realizing what the grownups didn't: the unassuming Porridge is actually the Emperor. As the emperor, he voice-activates the bomb, summons his ship to carry everyone to safety, and destroys the planet along with millions of Cybermen. In the end, the Doctor and Clara don't really seem that necessary to the plot, since Emperor Porridge could have saved the day from the start. It all comes across like an excuse to get the Doctor possessed so that Mr. Clever can blab things to Clara about being the Impossible Girl, but she seems only vaguely curious about it.
The TARDIS arrives at a mockup of the first Moon landing, complete with a cutout of the Earth in the background. The door opens, and the Doctor and Clara peer outside. Artie and Angie -- the delightful children who blackmailed Clara last week -- also take a peek. The Doctor leads them out with a flourish. "Well, here we are! Hedgewick's World: the biggest and best amusement park there will ever be!" Artie looks delighted, but Angie radiates such ennui that I am compelled to call her this for the rest of the weecap. "Your stupid box can't even get us to the right place," Ennui moans. She thinks it's some sort of moon base, but the Doctor says it's a "Spacy Zoomer" ride. A door opens in one of the larger rocks and out pops a man who looks like the human incarnation of the White Rabbit. He's disappointed to learn that they're not the cab service he called for some six months ago.
A group of soldiers barges into the scene, barking commands and raising their guns. The Doctor shows off his Golden Ticket to the park, but the soldiers don't care. "This planet is closed by imperial order," says the platoon captain. So the Doctor shows her his psychic paper, which relaxes her a bit. "Welcome, Proconsul," she says. "Any news of the Emperor? We pray for his return." The Doctor blathers something noncommittal in response, which is good enough to send the platoon away. The White Rabbit leads the Doctor and his gang off to what used to be the amusement park, but what now looks like a teetering junk heap.
The White Rabbit then takes them to something like a sideshow. It appears to be his establishment, only he arrived after the park had shut down. "Welcome to Webley's World of Wonders," he says. It's comprised mostly of wax statues and random artifacts. There's also a chess-playing Cyberman, the sight of which sends the Doctor leaping into action to protect his charges. The Cyberman gazes balefully at us -- or as balefully as one can with empty holes for eyes -- and into the opening credits.
"No need to panic," Webley says. "We all know there are no living Cybermen." Artie sits down to start a chess match while two little beasties watch from across the room. They look like robotic silverfish, as if regular silverfish weren't bad enough. Ennui figures out that there's someone underneath the Cyberman. Sure enough, the Doctor pokes around a bit and discovers Warwick Davis hiding in a cabinet beneath the Cyberman. "They call me Porridge," he says, crawling out from the cabinet where he's been operating the Cyberman. Webley gives Ennui an Imperial penny, eliciting a bit of a smile from her. Everyone sets off to explore the rest of Webley's Wonders, which include other defunct Cybermen and a statue of the Emperor.