Doctor Who Season 4 Episode 13

(The Doctor takes Rose, Jackie and the New Doctor back to Bad Wolf Bay)
Rose: Hold on. This is the parallel universe, right?
The Doctor: You're back home.
Donna: And the walls of the world are closing again now that the reality bomb never happened. It's dimensional retroclosure. See? I really get that stuff now.
Rose: I spent all of that time trying to find you. I'm not going back now!
The Doctor: But you've got to. We saved the universe, but at a cost, and the cost is him. He destroyed the Daleks. He committed genocide. He's too dangerous to be left on his own.
New Doctor: You made me!
The Doctor: Exactly. You were born in battle, full of blood and anger and revenge. Remind you of someone? That's me when we first met, and you made me better. Now you can do the same for him.
Rose: But he's not you.
The Doctor: He needs you. That's very me.
Donna: But it's better than that, though. Don't you see what he's trying to give you? Tell her, go on.
New Doctor: I look like him. I think like him. Same memories, same thoughts, same everything. Except I've only got one heart.
Rose: Which means?
New Doctor: I'm part human. Specifically the ageing part. I'll grow old and never regenerate. I've only got one life, Rose Tyler. I can spend it with you, if you want.