Stepping in, Paul wasn't sure whether to wear a stern face or an apologetic one.  In the end he chose to appear neutral, and to let the encounter guide him.  After all, he was hardly in a position to take a moral high ground right now.  Yet as a father, he had to, lest he lose his ability to be a parent.  "I heard yelling down here.  Carlie, I know that you're upset," he said, looking at his youngest daughter (as she seemed the only one of the two in the open right now).  "I understand.  And I'm sorry if I've hurt you.  But you need to calm down and talk with your sister and I about this.  Please, just tell us about how you're feeling - and at a conversational volume.  We can work through this, honey.  I promise we can, as a family."