The Cyberman brings Ennui to its lair, where Webley and Artie have already been implanted with Borg-like facial doohickeys. "Please stand by," Artie drones. "You will be assimilated... er, I mean, upgraded." Ennui screams. At least she's not bored anymore.
Clara and the Captain consult a cartoon map of the amusement park to find a defensible location and settle on Natty Longshoe's Comical Castle. It has a moat and it's close to the bathrooms! The Captain is iffy on the prospect until Porridge takes Clara's side.
The Doctor returns to Webley's showroom to search out one of those silverfish. He sonics it and picks it up by the tail. "Not even a cybermat anymore, but a cybermite." He scans it to find the frequency of its home base, but ends up transporting himself to the Cybermen lair. There, he finds the children blissfully zombified and silent. (He's not as happy about it as I am.) "We needed children," CyberWebley says. With the park closed, they were running low on kids until the Doctor came. "Hail to you, the Doctor, savior of the Cybermen!" Oopsie!
He explains that the Cybermen have been repairing themselves with this facility, using park patrons as spare parts. "We needed children to build a new Cyberplanner. A child's brain with its infinite potential is perfect for our needs." Too bad Clara didn't have another one of those "infinite potential" leaves in her scrapbook she could trade off. "But we no longer need the children," says CyberWebley. The cybermites have scanned the Doctor's brain and found it very promising, despite the fact that it's not human. Thanks to their continuing upgrades, the Cybermen can use almost any living components. CyberWebley flings a handful of cybermites at the Doctor, who proceeds to flail about as if he's got ants in his pants. Robotic ants, even. By the time the mites are done with him, he's got half a Borg face like the others.
"Get out of my head!" the Doctor commands, but the Cyberplanner is enjoying its new home. They meet face to face in their shared brain. "Who's Clara? Why are you thinking about her so much?" asks the Cyberplanner. The Doctor erects a mental block that keeps the cyber presence from completely taking over his mind, despite its best efforts. "I'm so clever already, and now I'm a million times more clever," gushes the Cyberplanner. "I could call myself Mr. Clever!" Mr. Clever pokes around and finds out about Time Lord regeneration, which allows us flashes of all the previous Doctors. The Doctor threatens to regenerate and short out all the Cybermen to which he's now connected. So they decide to play... chess. Chess, to decide who gets control of the Doctor's brain. I prefer Chutes and Ladders to decide life and death matters, but whatever.