How Does The Flight Of Duncan's Sons Play Into Macbeth's Hands

There is a big question about the murder of King Duncan. What good would it do Macbeth to murder him when his son Malcolm was his obvious successor. Did Macbeth plan to murder all three--Duncan, Malcolm, and Donalbain--on the same night. Shakespeare did not seem to be planning very far ahead when he was writing the gripping scenes leading up to the murder of the King. It would appear that Shakespeare was counting on his own powers of invention to help him out. 

Shakespeare seems to have given Macbeth a few cryptic lines to suggest that he does have plans to do something about Malcolm and Donalbain but doesn't want to think about them at the moment. These lines are contained in the following dialogue in Act 1, Scene 4:

DUNCAN:
Sons, kinsmen, thanes,
And you whose places are the nearest, know
We will establish our estate upon
Our eldest, Malcolm, whom we name hereafter
The Prince of Cumberland; 

MACBETH:
[Aside.] The Prince of Cumberland! That is a step
On which I must fall down, or else o'erleap,
For in my way it lies. Stars, hide your fires;
Let not light see my black and deep desires:
The eye wink at the hand; yet let that be
Which the eye fears, when it is done, to see.

Macbeth knows Malcolm would succeed his father, and, for that matter, Donalbain would succeed Malcolm if anything happened to his older brother. The lines Macbeth speaks to himself in an aside are intended to suggest that Macbeth must be planning to murder Duncan and his two sons that same night. He will never have another such opportunity. But Shakespeare evidently did not want to tell the audience what Macbeth was planning, simply because Shakespeare didn't know himself! He had enough to worry about with the murder of the King.

Shakespeare was a very busy man. He was not just a writer but a director, producer, casting director, manager, part owner of the theater, and even an actor. He probably had to work on his scripts when he could find the time and could not plan them out fully in advance. If he painted himself into a corner, so to speak, he had to rely on his genius to paint an escape exit on the wall to get him out. In other words, he probably didn't know how he was going to deal with Malcolm and Donalbain but was relying on his muse to help him--and she did!

When Macbeth has a meeting with Banquo in Act 2, Scene 1, he seems to be sounding Banquo out about joining him in his plot. Macbeth would like very much to have some help in dispatching three victims on the same night. But Banquo makes it clear that he is completely loyal to Duncan. Then when Macbeth finally kills Duncan, it would appear that he could not go ahead with murdering Malcolm and Donalbain (if that was what he planned) for a variety of reasons.

• He lost his nerve. He was so horrified by what he had done to Duncan that he began hallucinating. When his wife tells him to take the two daggers back to Duncan's chamber and smear the grooms' faces with blood, he says: "I'll go no more. / I am afraid to think what I have done; / Look on't again I dare not." He is in no condition to commit two more murders.


• Macbeth thinks he has heard a voice crying "Sleep no more!" loud enough to wake up the entire house. This is probably his imagination, but it is just as effective in preventing him from prowling around the corridors as if it were real.


• Then begins that ominous knocking at the gate which becomes louder and more insistent. It will wake up everybody in the castle, including, no doubt, Malcolm and Donalbain.


• It is noteworthy that Macbeth asks his wife, "Hark! Who lies i' th' second chamber?" She tells him Donalbain. He isn't even sure where to find the two boys.

So after the body is discovered, Shakespeare has Malcolm and Donalbain decide to flee for their lives. He didn't want to show Macbeth killing two young boys because he wanted to preserve some modicum of audience sympathy for his hero--and he knew he would lose it if he showed Macbeth killing two innocent boys in their beds. This expedient seems to have been a last-minute inspiration of Shakespeare's. It works perfectly because he can blame Duncan's murder on his sons. The idea is that they hired Duncan's two grooms to kill their father. They are not there to defend themselves, and Macbeth has killed the grooms to keep them from giving any testimony. No doubt many people, including Banquo, suspect Macbeth of being responsible for Duncan's death. But Macbeth manages to get elected Duncan's successor, and after that he doesn't care what people think--and they all know they had better not say what they are thinking anyway.