You start off your conversation around Marna, and how you have enjoyed your time spent with her.
"Yes, she has spoken to me warmly of your village festival, and the time you spent with her at a recent feast." He smirks at you. "It seems as if you have caught her attention, young Sir Stone."
You acknowledge that, in fact, that was your original reason for setting up the visit, but you have darker news to share with him before you speak of courting. You bring up the assassination attempt, and that you fear that someone is either framing the Count, or... you left it unsaid, but your meaning is clear.
The Duke rubs his eyes, wearily. "I do not know precisely how to deal with this, Sir Stone. As you mentioned, all of this evidence is circumstantial. However, given my understanding of Count Foles' character... this is quite troubling, indeed. Your discovery of such rich minerals would certainly give him a motivation... but... for such a serious charge, I would need irrefutable evidence to take action.
"For now, I can only say this. Watch your back, Sir. Do not give... whoever is responsible... another chance to strike you so cleanly.
"Regarding Marna... I have no objections to your courting her, and visiting her here in my lands. But, until this situation is remedied, I hope you understand that I cannot abide her visiting you in your lands."
Anything else you would like to talk to the Duke about?