"You still are," the Doctor said. "Just because---just because people go away, it doesn't stop them being part of you."

It was something Sarah had said to him once, when he talked about leaving. It made so much sense, now. He could almost imagine her saying it to him. How everything had a time and everything ended.

He gave Alan a small smile. "We might never see Sarah Jane Smith again, Alan. But we saw her. She was part of us, and she always will be. That's her immortality. And it's in us."