Schuyler Fox: Lovely woman. I think we might have had a date once. Or maybe we just exchanged letters. Joe Fox: You wrote her letters? Schuyler Fox: Mail. It was called mail.
Joe is talking about the owner of the bookshop around the corner. Joe's grandfather reminisces about the owner way back when, which is Kathleen's mother and how they might have dated once and wrote actual letters to each other.