To be thus is nothing;
But to be safely thus.

– William Shakespeare

Macbeth, Act 3, Scene 1. In his soliloquy after Banquo’s departure, an insecure Macbeth expresses concern about his position as King of Scotland. Being king is nothing, if he can’t remain king, he says. He clearly is mistrustful of Banquo and views him as a threat to his continuing rule. This suggests that he may plan something against Banquo.