to save the world
(What use are emotions if you cannot save the woman you love?)
He didn't know what to do.
If he could have switched places with her - if he could have placed himself at the mercy of a Dalek (the mercy of a Dalek? Under other circumstances, the idea would have been almost funny) so that Rose could live - then he would have done so in a heartbeat. She was just a girl, after all, with her life (just the one) ahead of her. But the situation couldn't be altered, and he had to deal with it now.
He didn't know what to do.
If I let it out, it might kill her anyway, he thought, but he was conscious even as he was thinking it that it was a weak effort at justification (why do you have to justify it by finding a reason to let it kill Rose, rather than thinking of all the lives that will be saved?). If he let Rose out, then there was still a chance that she could survive. If not, there was no hope at all.
He looked down at the screen again, and Rose stared back at him, afraid but determined.
If I let it out, there's no telling how many people will die. If I don't, then Rose...
He closed his eyes. Rested his finger on the button.
(for what I am about to do...)
"I'm sorry, Rose," he whispered, and he cut the visual link.