"There's always one thing I meant to ask Jack, back in the old days. I wanted to know about that Doctor of his. The man who appears out of nowhere and saves the world, except sometimes he doesn't. All those times in history when there was no sign of him. I wanted to know why not. But I don't need to ask anymore. I know the answer now. Sometimes the Doctor must look at this planet and turn away in shame. I'm recording this in case anyone ever finds it, so you can see... you can see how the world ended."
The recording ended there. The Doctor stared at the image of the woman on the screen.
"Gwen Cooper," he muttered to himself, recalling the girl's name easily; it hadn't been that long for him since she'd helped him against Davros and the Daleks. He sat in his chair, thinking to himself, wondering about what she had said. It was true that the four five six encounter was a major point in the history of the Human species, but there was something else that kept him from getting involved. For a moment, he thought it might have been shame, that he was ashamed of the humans for acting as barbarically as they had. It was true, but there was something else, something bigger than that.
"Gwen Cooper," said the Doctor, looking into her face. He knew she couldn't hear him, but he had to say it. "I'm not ashamed. I'm afraid. I know if I interfere, I won't stop. I'll make myself a god, and you'll never have to fight your own battles again. That isn't fair, is it? I can't let myself become Rassilon. No matter how much I want to." The Time Lord sighed, turning off the monitor. The words of the Ood echoed in his mind; your song is ending. Maybe it was time it did end.