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Key plotpoints are pictured below. You have been warned!
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In the previous episode, the Doctor and his companions Rose and Mickey crash-land in a parallel universe. The Doctor isn’t happy.
John Lumic, the owner of Cybus Industries, has developed the “ultimate upgrade”… a process that entails chopping out your brain and bonding it to a suit of armor. The Ethics Committee of Great Britain is aghast.
Lumic’s prototype Cybermen crash the birthday party of Rose’s parallel world mother, Jackie, offering everyone a free–compulsory–upgrade. The Doctor tries to calm things down, but the Cybermen reject his offer.
The Doctor and co. (including Rose’s ersatz dad, but minus Jackie) manage to escape. Lumic utilizes his hypnotic Bluetooth technology to compel the people of London to willingly submit to the upgrade process.
Mickey infiltrates Lumic’s Zeppelin, tied to the roof of his conversion facility; Rose and her “dad” fail to save Jackie from being upgraded; and the Doctor discovers the Cybermen’s secret weakness–an emotional inhibitor that prevents them from understanding what they’ve become.
The Cybermen order Lumic upgrade himself. When he refuses, they forcibly upgrade him. The Doctor, Rose, and Pete are captured by Cybermen and taken to see Lumic–the newly minted Cyber Controller.
Mickey decrypts the code that will deactivate the emotional inhibitors. He sends the code to Rose’s cell phone. The Doctor plugs Rose’s phone into a control console and blasts the shutdown code throughout the Cybus network. Every Cyberman–except for the Controller–is killed by the emotional shock.
While the conversion facility burns, the Doctor and his friends climb a rope ladder up to the Zeppelin. The Cyber Controller follows them!
They cut the ladder, sending the Cyber Controller plummeting into the burning factory and his apparent destruction.
Mickey decides to stay in the parallel world to help destroy the remaining Cyber factories and help his blind, parallel-world grandmother. The Doctor takes Rose back to her earth, and her own, non-upgraded mother.
Tomorrow: Doctor Who, Cybermen, and the bane of product managers everywhere: Product Narcissism.
“The Age of Steel” is collected in…
The original “coming attractions” for this episode…