He doesn't want to die. Who does, really? But he, especially, does not want to give up. Not after so long. He has so much left to get done, so many more people to save. If he has to go, though, he's taking those abominations with him.
He chances a glance over at Rose. He doesn't want to take her with him. He's lived nine-hundred long years, nine lifetimes from her small perspective. She's nineteen years old, and she's about to die.
She doesn't deserve this death sentence. What's worse is that he brought her here. Accident or not, he knew that the life he lived was dangerous, even more so for someone unused to it. He'd done it again, let down someone he cared about. Just another stupid, stupid mistake to line up with all the others.
Part of him doesn't want to do what he's about to do. Part of him wants to keep her there, selfishly, so he'll have some light in his final moments, but the rest of him knows that would be cruel.
He's done a lot of thinking: you tend to do that when you're on your own. But he's never thought about death. He's always assumed that any dangerous situations he found himself in would allow him to regenerate. Unfortunately, being blown up is not one of them.
He doesn't want the timelords to die with him, but they're already long gone, put down to myth and legend. Yes, he has to do this. But the question is, how will he get her to leave?
"Suppose," she says, obviously thinking.
"What?" he asks, heart racing. If she's about to say what he thinks she is…
"Nothing."
She turns away, but he's not about to let this chance go by.
"You said suppose."
"No, I was just thinking. I mean, obviously you can't, but you've got a time machine. Why can't you just go back to last week and warn them?"
"As soon as the TARDIS lands in that second, I become part of events, stuck in the timeline."
"Yeah, thought it would be something like that."
Her face falls. Evidently, whatever plan she had in mind was crushed.
"There's another thing the TARDIS could do," he suggests, and for the first time in his long life he actually means it. "We could leave. Let history take its course. We could go to Marbella in 1989."
"Yeah, but you'd never do that," she says with a ghost of a smile.
They'd only traveled together a short time, but she already knows him so well. Even though he'd said it, he knew he couldn't just let it happen.
"No, but you could ask. Never even occurred to you, did it?"
She shakes her head, and he can't help but smile a bit himself.
"Well, I'm just too good," she says.
There is a hum, and his eyes light up. He might have a chance at saving the world after all.
"The Delta Wave's started building. How long does it need?"
They run over the console. He taps a few things into the device, but he already has all the information he needs. The Delta Wave is nearly ready, but without more time, the precision is wrecked. He can't refine it. It will blow up everything in its path—the fleet, the ship and Earth.
"Is that bad?" she asks.
He looks at her, and he doesn't have to say a word.
"Okay, it's bad. How bad is it?"
He grins, even though it's the last thing he wants to do right now, and Rose does as well.
"Rose Tyler, you're a genius!" he says, kissing her on the top of the head, because who knows when he'll have a chance to do that again? "We can do it…if I use the TARDIS to cross my own timeline…yes!"
They race over to the TARDIS and he positions her in exactly the right place to insure it will travel to the correct time and place. It wouldn't do to get her caught in the French Revolution or twenty years in her future.
"Hold that down and keep position," he orders.
She nods. "What's it do?"
"Cancels the buffers," he lies. "If I'm very clever-and I'm more than clever, I'm brilliant—I might just save the world. Or rip it apart.
"I'd go for the first one," she said, grimacing.
"Me too," he agrees. "Now, I've just got to go and power up the Game Station. Hold on!"
He runs out of the TARDIS for the last time. About midway across the room, he turns around and levels the sonic screwdriver at the TARDIS. The engines start with a roar. The door slam shut. He turns away.
"Doctor, what're you doing?" she shouts. "Can I take my hand off? It's moving."
Her voice grows more and more desperate as she realized what he's done. The very last words he hears from her are "Doctor, let me out!"
He returns to work. He might destroy the world in five minutes, but at least he managed to keep her safe.
As a complete newbie to this fandom, I'm going to assume that the regeneration process can only take place when there is a body to regenerate. If something happens (like being blown up) there is no body to regenerate, and thus you can't. It's probably not canon, but it's the best explanation I have for the hologram later in this episode.
Please let me know what you think! I don't really like present tense, but it works for this one-shot.