Jackson Lake begins to weep: in the middle of a nightmare, something stolen and something lost, in all that fire and electricity, the information, the regeneration of himself to himself, becoming something else. A man who could cope, who laughed at danger. Who loved it more and more, the worse it got, and would never let loss keep him from saving the world. There are a million ways to regenerate. It's not always so flashy. "I am nothing but a lie," he says, crumbling, and the Doctor shouts, grabbing at his hands. "No no no no no! Infostamps are just facts and figures!" He shivers, terrified, as the Doctor points wildly: "All that bravery! Saving Rosita!" Defending London Town. "And the invention, building a TARDIS... That's all you."
His chin comes up, that lovely chin, and he blinks it away; his alchemy turns fear to angry and thence to purpose, and so it is that Jackson shivers now with purpose. "And what else? Tell me what else, there's still something missing, isn't there? I demand you tell me, sir. Tell me what they took." But they both already know, and even as the Doctor apologizes, Lake starts going catatonic. "Infostamp's plain technology. It's not enough to make a man lose his mind. What you suffered is called a fugue. A fugue state. Where the mind just runs away, because it can't bear to look back."
Jackson hears him, in there, and fights his way to the surface, closes his eyes, trying to listen. To hold onto it. "You wanted to become someone else, because Jackson Lake had lost so much..." The bells ring, in the cloisters, and Rosita calls it midnight. Christmas Day. It brings Jackson Lake back to himself. It is a birth, and it is a tragedy, and that's what regeneration means. That is what change is.
"Oh my God," say he, and remembers his wife. She was murdered, that night he lost his mind. Lost time. "Caroline," he mumbles, as the Doctor watches, and he looks up into those eyes. "They killed my wife." Rosita cares for him while the Doctor looks on, while he loses it, but soon enough the infostamp starts beeping, and then there's another, like easter eggs hidden around the place. The Doctor pulls out a bandolier of them, a whole cache, and moans in awe. But why are they beeping? "Activation. A call to arms... The Cybermen are moving!" The Doctor runs into the street, and sees something in shadows against the wall: by firelight, after Christmas has been packed away for the night, a line of people being marched somewhere, against their wills.