Macbeth is king. The three things said on the heath have all come true. And something else was said in that same place.
Banquo would be the father of kings. By those words another man’s house takes the fruit of what he did. Newly crowned, that is the first thing he thinks of.
He invites Banquo to the evening’s feast. Where are you riding, when will you be back, he asks pleasantly. When Banquo goes out, he sends for someone.