GWEN: There's one thing I always 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 any more. I know the answer now. Sometimes the Doctor must look at this planet and turn away in shame.

ODUYA [on monitor]: Then let me ask, not as a representative, as a father. You need these children. We've seen you hooked up to that boy, but why? Are they keeping you alive?

456: No.

ODUYA: Then what are they for?

456: The hit.

ODUYA: I don't understand.

456: The hit. They create chemicals. The chemicals are good.

ODUYA: Good in what way?

456: We feel good. The chemicals are good.