Given scene/plot descriptions from movies or TV shows, and given a specific question about the scene, summarize the question into a title

In Source Code, I did not get the meaning of a conversation between Capt. and Christina in the train. It was between roughly 00:42:00-00:43:00 The conversation was as follows: Capt- Okay. Christina? Um...I've been having these dreams lately. Really vivid. And you've been in them. Christina- Really? Capt- What? Oh. No. Not like that. Not that I wouldn't. I...It's just...Um.. So what was it that he wanted to say, but could not complete and why Christina left him without listening to him completely. I could not get that part.
What does the conversation mean?