In Act 3, Scene 1, Macbeth asks Banquo about his plans for the day. It is interesting to note that Macbeth asks his most important questions last in two of their exchanges, making them seem like an afterthought and only polite conversation.
"Is't far you ride?"
"Goes Fleance with you?"
People often wait to bring up whatever is really on their minds. For instance, a telemarketer will ask your name and then ask, "How are you today?" As if he cared! And finally he will get around to asking for your donation or whatever he is really calling about. Shakespeare understood human nature, and we can learn some important lessons on that subject from him.
Banquo would certainly not want to leave Fleance alone in Macbeth's castle. Macbeth has two men waiting to talk to him about murdering Banquo and his son. He has to kill both of them. He can hardly kill Banquo and blame Fleance for it; he has used that trick already, and Fleance is too young anyway. Macbeth is fishing. Or phishing. He is trying to figure out the best time and place to ambush Banquo and Fleance. Banquo is courteous, as required by Macbeth's new position, but he doesn't trust him at all. Banquo terminates the conversation by saying, "Our time does call upon's." In other words, "I have to go. We'll be late." We all tell white lies like that. In order to get away from Mr. Spencer, Holden Caulfield lies about having to go to the gym to pick up some equipment in The Catcher in the Rye, and then in order to get away from from the too friendly Mr. Antolini, Holden lies about having to pick up his luggage at the train station. Banquo wants to get away and to avoid providing Macbeth with any further information about his travel plans. Banquo would probably prefer not to return at all, but Macbeth has virtually ordered him to return for the coronation banquet.
Tonight we hold a solemn supper, sir,
And I'll request your presence.
Fail not our feast.
Macbeth talks to the two murderers right after Banquo exits. Macbeth has to be able to tell them where to set up their ambush. He can't just get them to agree to kill Banquo and Fleance and leave the rest up to them. When the two murderers are joined by a third one sent by Macbeth, the Second Murderer says:
He needs not our mistrust, since he
Our offices and what we have to do,
To the direction just.
After Macbeth and Lady Macbeth hasten the prophesy of the three witches that he will be king by slaying Duncan, Banquo wonders to himself if the other prophesies of the "weird sisters" will also be realized.
As upon thee, Macbeth, their speeches shine—Why, by the verities on thee made good,May they not be my oracles as well,And set me up in hope? But hush, no more. (3.1.7-10)
Our fears in Banquo
Stick deep, and in his royalty of nature
Reigns that which would be fear'd: 'tis much he dares...
Whose being I do fear; and under him
My genius is rebuk'd, as it is said
Marc Antony's was by Caesar" (3.1.49-55)