The TARDIS appears on a London street, in the snow. The Doctor leaves, leading Yuri and Mia and the robot and Adelaide out, shivering. Adelaide stays far away from him; Mia looks sick and Yuri's unsure. "Isn't anyone going to thank me?" he asks, and something goes cold in Adelaide. The robot dies quickly, having lost his signal altogether.
"Don't you get it? This is the 21st November, 2059! It's the same day on Earth. And it's snowing! I love snow." Mia loses her shit, freaking out about the TARDIS, and finally runs off down the lane. Adelaide sends Yuri after her, and turns to stare at the Doctor, horrified.
"Just think, though. Your daughter, and your daughter's daughter, you can see them again. Family reunion!" But Adelaide knows -- knows, now -- that she's supposed to be dead. "My granddaughter, the person she's supposed to become... Might never exist now." The Doctor blows her off, promising that Captain Adelaide can inspire Susie face-to-face now. "Different details, but the story's the same." Adelaide points out that, by his own explanation, he can't know that. And if the Brookes changes, the whole of history could change, the future of the human race could change. These moments are precious, and fixed. "No one should have that much power," she says, and is greeted by a face very few have seen. The Racnoss Empress saw that face, and feared it. He saw that face once, when his wild twin killed the Daleks for the third and last time, and it scared him to death. That's the face she's seeing now. It is ugly.
"Tough," says the Time Lord.
She steps away. He's no good. He's scary. "You should have left us there." He tries to become smaller, tries to sound rational, tries to ball up all this nervous energy and make himself presentable; he tries to sound reasonable, to justify himself. "Adelaide, I've done this sort of thing before. In small ways. Saved some little people. But never someone as important as you. Oh, I'm good!" The Doctor licks at his chops.
The Doctor gets angry. Angry is so much better than lonely, or hurt, or terrified.