The knocking continues, but the porter does not immediately open the door. Instead, he plays a game with himself in which he imagines himself as the porter of hell and jokes about the kind of sinners he might let in. Eventually, however, he opens the door to Lennox and Macduff, who have been commanded to call upon the king to arrange the royal departure. It is early morning, and most of those in the castle are still asleep. One who is not is Macbeth, and he directs Macduff to the king's chamber. Only a moment passes before the news breaks: King Duncan has been murdered.
On hearing the terrible revelation, the Macbeths' acts are beyond suspicion, but Macbeth admits to having killed the guards of the King's chamber — not part of the original plan — and Lady Macbeth faints. The assembled thanes of Scotland resolve to avenge the act of treason. Duncan's sons, Malcolm and Donalbain, thinking themselves open to the charge of murdering their father, plan to flee to England and Ireland.
