The first scene deals with Macbeth's thoughts as he ponders the terrible act he is about to perform. He has spoken to Banquo who told him that he had dreamt about the witches and Macbeth had asked him that they speak about them at an opportune time. Macbeth also informed Banquo that he will bring him great honour should Banquo support him. Banquo tells him that he will maintain his love and allegiance to his king, if he should be involved in any discussion. This implies that he might suspect that Macbeth is up to no good.
Once Banquo has gone to bed, Macbeth, in at the beginning of a soliloquy, mentions that he is waiting for the signal from Lady Macbeth to proceed to Duncan's chamber and murder him. It is at this point that he imagines seeing a dagger float in front of him. Macbeth is clearly in a terribly anxious state and the hallucination he sees is, to him, 'a dagger of the mind, a false creation proceeding from the heat oppressed brain.' He realizes that it is an optical illusion, but it becomes more defined for he then sees gobs of blood on its blade. He realises that it is the horror of the moment - the silence and the terrible act he is about to commit - that creates this ocular fantasy. He asks for the cobblestones in the courtyard to hide the sound of his footsteps in the eerie silence. He then states that as long as he is only a threat, Duncan remains alive, meaning that he has to kill him soon.
When the bell rings, he responds and mentions that once he goes, the deed will be done. He asks that Duncan not hear its sound because it is the last thing he will hear - the sound that signals his departure to either heaven or hell.
Scene two opens with Lady Macbeth's thoughts in which she expresses that she had done her part and that she was inspired by the drink that she had given Duncan's guards to make them drunk. she mentions the owl's cry which is a portent of Duncan's death Lady Macbeth has left the doors to his chamber open and she realizes that her husband is committing the heinous deed. She has also drugged the guards drinks which could even kill them - death or nature will determine if they survive.
The tense atmosphere leads to Lady Macbeth getting a fright when she hears her husband. She fears that the guards have awoken and that they had not been successful. She hopes that Macbeth had found the guard's daggers which she put at the ready and declares that she would have killed Duncan herself if he did not resemble her father so much.
When Macbeth arrives he tells her that he had killed the king and anxiously asks her if she did not hear a noise. She says that she only heard the owl shriek and the crickets cry. The two are very tense and nervous. When Macbeth looks at his bloody hands he comments on what a sorry sight they are and Lady Macbeth quickly corrects him, saying that it is a foolish thought. Macbeth shows how truly distraught he is by mentioning that he could not say 'Amen' and that he had heard voices after killing Duncan. His wife seems to be more in control and tells him that he is acting cowardly.
Lady Macbeth tells him to wash the blood off his hands and asks why he had brought the guards' daggers with him and that he should return them. Macbeth refuses to go back and she offers to return the daggers and smear them with Duncan's blood to implicate them. Macbeth is obviously unnerved and when he hears knocking, he wishes that it could wake Duncan. He is clearly disgusted with himself for what he had done.
When Lennox and Macduff enter, Macbeth tells them at some point that it had been 'a rough night' - clearly an ironic statement. when Macduff discovers Duncan's bloodied corpse and cries out to awake everyone, Lady Macbeth acts the innocent and enquires what is causing the uproar. Macduff kindly tells her that it is not for her gentle ears to hear. Macbeth makes quite a speech about how wonderful Duncan was and that all that was important to him had ceased to exist, the moment Duncan died.
Macbeth then confesses that he had killed both of the guards out of anger and when Macduff wants to know why, he makes a speech about how he could not help himself to see the guilty guards lying there with Duncan's blood all over them. He suggests that no man who was loyal to Duncan could have resisted from lashing. He had slain them as a matter of honor and duty. To distract attention away from her husband, lady Macbeth seemingly faints and is carried away.