The end (spoiler...duh)
Carol asks Peter 'what are you thinking about?' and he answers 'about kids', what does he mean by that? What kids? I can't imagine he's thinking about what happened to Elizabeth, or what he saw when he himself was a child, or his childhood friend who killed himself, his daughter and what happened to her etc, and says this to Carol with a big smile...?
Or maybe they're moving on and there is a kid on the way?