The Doctor is so sad, as his stupid brain files past everything in slow motion: Their hope, their strength. Their unending rushing around: is it something to be proud of, or just useless folly? He could cry, wondering, watching them stuck in their story. Playing it out again and again, right before his eyes. Adelaide watches him, and wanders why he won't leave, as they move so slowly. He carries his spacesuit out into the lock.
As Ed runs to the shuttle, the airlock closes around the Doctor and refuses to open. "Tell me what happens," comes the voice of Adelaide, and he swears he doesn't know. She's getting angrier as he continues to protest his ignorance, finally offering to crush him in the airlock's pressure. "Except you won't. You could have shot Andy Stone, but you didn't. I loved you for that." She stares; he looks at nothing. "Imagine... Imagine you knew something... Imagine you found yourself somewhere, I don't know, Pompeii. Imagine you were in Pompeii. You try to save them, but in doing so, you... Make it happen. Anything I do just makes it happen."
Steffi calls her away, but she looks up with her strong gaze and unflinching beauty and she punches him to the main screen, to look him in the face. "You're taking Action One. There are four more standard action procedures." And Action Five is detonation. The final option: the nuclear device at the heart of the Central Dome. "Today, on the 21st November 2059, Captain Brooke activates that device, taking the base and all her crew members with her." She stares. "No one ever knows why."
"But you were saving Earth. That's what inspires your granddaughter. She takes your people out, into the galaxy, because you die on Mars. You die, today. She flies out there," he says indulgently, because now he knows what it is to love Adelaide Brooks: "Like she's trying to meet you". Adelaide promises, swears, begs, dares, commands herself, commands the universe: "I won't die. I will not." But your death creates the future, he says. She speaks without pride. "Help me." And the Doctor stares, as she's nearly weeping.
"Why won't you help, Doctor? If you know all of this, why can't you change it? Why can't you find a way?" But he interrupts her. "Sometimes I can, sometimes I do, most times I can save someone, or anyone. But not you. You wondered all your life why that Dalek spared you, I think it knew: Your death is fixed, in time, forever. And that's right." Bargaining now, she reminds him that he'll die too, but at his protest she snarls, "What's gonna save you?" And oh, the look in his eyes when he tells her exactly who.