premise: David had obviously always known and Julia had learned that, whatever feelings were churning around inside his mother's mind, it was vital for her that they remained private. David was holding the strings in a pattern Julia had never seen before. His face seemed to show nothing except benevolent interest but Julia could tell from the way that he was carrying his head and a certain tension in his body that they were approaching a crisis point.
hypothesis: David and his mother were approaching a crisis point