Clara goes back to leading the soldiers and instructs them to drop a power line into the moat to electrify it. The Doctor soon summons her back inside the castle and tries to get the bomb trigger from her. "Prove you're you," she says. He gets very mush and tells her how pretty she is and how much he likes her. She leans in as if to kiss him, then slaps him hard because she knows it's not the Doctor talking. She seems quite smart for all of two seconds, then waggles the trigger at him, which Mr. Clever is able to grab from her and destroy. Outside, millions of Cybermen gather, secure in the knowledge they can no longer be bombed into scrap.
The first one steps into the moat and gets electrocuted. Clara and the soldiers see this and laugh with delight. Then the electrocuted Cyberman upgrades itself and all the rest of its brethren, and they all begin crossing the moat with ease. While the soldiers fend off the Cybermen as best they can, Porridge sneaks off to find the bomb.
Back at the chess match, the Doctor sacrifices his Queen in exchange for the Cyberplanner releasing the children. Nooooo! "The Time Lords invented chess," the Doctor says. "If you don't avoid my trap, it gives me mate in three moves!" Bobby Fissure over here doesn't see how this is possible. There's much flailing back and forth as they argue. Mr. Clever decides to power down all the Cybermen so he can call on their combined processing power. This happens just in time to keep Clara and the soldiers from being "upgraded" into the Cyberiad. The Doctor plucks a hand-dealie off Porridge. He outlines his three-move plan: "Move one: turn on sonic screwdriver. Move two: activate pulser. Move three: amplify pulser!" He then slaps himself upside the Mr. Clever side of his head, which I think makes four moves, not three. Really, it's five if you count taking the dealie from Porridge.
Clara runs in just as the Doctor has taken control of his whole mind again. Just to be sure, she asks, "Do you think I'm pretty?" "No, you're too short and bossy and your nose is all funny," he says. She's relieved to hear it and quickly unties him. They set about destroying the planet before the Cyberplanner can regain consciousness inside all the Cybermen. The Doctor ponders how he'll be able to active the bomb now, without the Captain. "I think you should ask Porridge," Ennui says, coming out of her coma. "Why?" Clara asks. "Well, he is the Emperor," she smugs. "Come on, it's obvious. He looks exactly like he does on the coin and the waxwork. Am I the only one paying attention to anything?" First, he doesn't resemble the wax statue at all. Second, shut the hell up, Ennui.