River is infinitely amused when he fidgets with his non-existent jumper. Amusement that fades to confusion as the conversation progresses. All of the Doctor's forms that she has encountered so far have known who she was, though not all of them knew what she was. "Don't get so flustered, sweetie. It's nothing I haven't seen before."

She leans in uncomfortably close, her eyes searching his for something, a spark of recognition, anything.

There was nothing. For some reason, that saddened her.

"I'm River Song and I am going to be a very important part of your future. You really haven't met me yet, have you?"