DOCTOR: I let him down. I did my best–

ACE: Well, it wasn’t good enough.

DOCTOR: I know… I know. And I’m sorry.

ACE: Do you even know what that means?

DOCTOR: Of course I know what it means! Everyone I’ve ever met. Everyone I’ll ever meet. They’re all dead, Ace. Every last one.

ACE: What are you talking about?

DOCTOR: Flick a switch, and I can reach a time when every soul that ever set foot inside the TARDIS is long departed. Or I could go back and see them. The times when they’re alive. Somewhere, somewhen, they’re all still there. Making tea. Walking the dog. Eating beans on toast. Living and breathing… Alive and dead. Everybody. All of the time. And none of the time. It’s how it’s always been for me. How it always will be.