"Not bad. But why the proposal?"
"Simple. I’m going to string her along until I can figure out her plan."
Her grin faded. “Are you sure that’s the right thing to do? I mean, what if you’re wrong? What if she genuinely wants to marry you? It’s going to be hard to call it off. Uh, you will call it off, right?”
"Just as soon as I figure out what she’s up to." Ned smiled sweetly.
Nancy paused a minute. “There’s something that really bothers me, Ned. Why didn’t you tell me about your crazy plan ahead of time?”
"I wanted to! I was going to explain everything at the pool party, but before I could you spilled the beans to Jessica about my proposal to you. She hit the roof. To keep her from getting suspicious, I had to make the announcement about my engagement to her."
"And just why did you propose to me the night before?”
Ned looked sheepish. “Well, it’s kind of silly—”
"Maybe to you! But let me decide for myself."
"Okay. The truth is, a long time ago I promised myself that the first girl I ever proposed to would be Nancy Drew. When I realized that I’d have to ask Jessica to marry me, I decided to keep that promise anyway."
"Oh." Nancy’s anger softened. "Tell me something else—did you know I’d turn you down?"
"I was pretty sure of it. As you said, it’s too soon."
Carolyn Keene, Nancy Drew Files #24: Till Death Do Us Part (1988)