In Macbeth, what shifts of behaivors did Banquo know about Macbeth?

As soon as the witches spill the beans about how Macbeth will become king, Baquo knows his friend thinks the crazy old hags might be onto something. Macbeth does allot of staring into space. Banquo comments, "look how our partners rapt". Macbeth also promises to sit down with Banquo and have a heart to heart. This never happens. Indeed Banquo goes so far to flat out say that the witches will betray him. That's what witches do, they betray people! Later Banquo makes it plain that he thinks Macbeth killed the king. Unfortunately it’s an aside (to himself) so nobody else hears it.