Set in Macbeth's courtyard late at night. Banquo and his son, Fleance, are walking to their bedrooms. Banquo has a feeling of anxiety towards going to sleep because he fears that he will dream of the witches' prophecies. Macbeth enters and persuades Banquo to talk about the prophecies with him sometime, although Banquo will not speak of anything disloyal to Duncan. When Macbeth is left alone in his courtyard, he sees a vision of a dagger. He is confused when he wonders where the dagger came from. Was it a real dagger, or was it just a vision in his mind? The dagger leads him to Duncan's chamber, at which time Lady Macbeth rings the bell, signifying that Duncan and his servants are asleep. The time has come for Macbeth to commit the crime.
In this scene, Lady Macbeth shows that she too is very tense. She required the help of alcohol and admits that she could not have committed the murder. When Macbeth returns from Duncan's chamber, Lady Macbeth takes control of her distressed husband. Macbeth is very worried about a sound that he heard, which apparently said, "Macbeth shall sleep no more." At this point in time, Lady Macbeth realizes that Macbeth is carrying the daggers which he was suposed to plant with the servants. Being unable to go back to the King's chamber, Macbeth allows Lady Macbeth to return the daggers to their appropriate places. At the sound of a knocking of the door, both Macbeth and Lady Macbeth return to their room and wash the blood off their hands and change their clothes. Macbeth is concerned about the fact that the blood apparently wasn't coming off his hands.
This scene is the famous "Porter Scene." The castle's porter is awakened by a knocking at the door. He, being drunk, eventually stumbles his way across the courtyard, he curses Macbeth, saying that Macbeth is the Devil and that he is the porter of the gate of hell. After the porter stops for a pee, he opens the door to reveal Macduff and Lennox. Duncan had asked them to come early and wake him up. Macbeth enters, wondering who had been knocking at the door. After Macduff is greeted by Macbeth, he heads toward the King's chambers. Meanwhile, Lennox is talking about the unnatural disturbances during the night. Macduff then returns and, in hysteria, announces that Duncan has been murdered. Everyone is awakened by the ringing of the alarm bell. Macbeth and Lennox go to investigate the scene of the crime and, in seeing the bloody corpses of the servants, Macbeth admits to have killed the servants in the rage of the death of their King. When Lady Macbeth hears of the murder of the servants she faints. She wasn't mentally preparing these murders to take place, Macbeth had not told her that he had killed them. The King's sons, Malcolm and Donalbain, silently escape to England because they sensed danger.
In this scene more is learned about the unnatural occurances of the previous night. To add effect to the day after Duncan was murdered, the sun has not risen. Macduff says to Ross that Malcolm and Donalbain are suspected of killing their father. He also says that Duncan's body was taken to be buried and that Macbeth was named king. Ross goes back to Fife to attend Macbeth's ascention, but Macduff decides that it would be better to not go back to Fife because he was afraid that the changes being made were for the worse.