[She opens her mouth to respond instantly and finds, irritatingly, that there is still no obvious thing that comes to mind. So, flustered and baffled and irritated at already somehow finding herself six strides behind, she goes with:]

If you are not here to ask something, then I must ask what you are even doing here in the first place, sir. What were the contents of this alleged letter? What is it, precisely, that you want?