Writing Prompt: Four Lines of Dialogue Between Two People

I came up with the following dialogue for a scene in a novella that I'm working on, and thought that if I stripped out the extraneous details it might make a decent writing prompt. What can you do with the following dialogue?

"How could you keep this from me?"

"You weren't ready --"

"What gave you the right to decide I wasn't ready to know?"

"You weren't ready to ask until now."

What's the secret? Who's keeping what from whom? Why wasn't the first person ready to ask until now? That's for you to decide if you decide to use this.