answer: Sara invites John's sister from France to John's birthday. #Person1# likes the plan. Sara tells #Person1# only when she's sure John's sister can come.
documents: #Person1#: Alright, Sara, we know that you are planning something big for John's birthday. Could you tell us just what you have in your mind?
  #Person2#: I want to make his birthday a very special event. John has a sister living in France. And I'll send her a plane ticket, so that she can be here for his birthday.
  #Person1#: Boy! What an excellent plan! That's something special. I kind of guessed you had some secret plan and were waiting for the right time to tell me.
  #Person2#: Well, I didn't want to say anything until I was sure she could come.