In Scene 1 of Act V, Lady Macbeth walks in her sleep, rubs her hands as if washing them, and says: "Out, damned spot! Out, I say." The spot is the blood of the crime: what she relives in her sleep begins with the murder of Duncan.
A Doctor and a Gentlewoman watch her. The Gentlewoman says she gets up, writes, reads, and seals a paper, all asleep, that there is always a light beside her, and that she has seen her rub her hands "for a quarter of an hour." In her sleep, she speaks of the old man's blood, of Banquo, and of Macduff's wife, and says: "All the perfumes of Arabia will not perfume this little hand."
The scene answers the night of the crime (Act II, Scene 2). There, Macbeth looks at his dirty hands and asks: "Will all of great Neptune's Ocean be able to wash this blood from my hands for good?" Lady Macbeth tells him: "A little water will clear us of this deed." In Act V, she is the one who cannot clean herself.
The Doctor concludes: "She needs spiritual help more than medical help." He asks the Gentlewoman to watch her, so that she does no harm to herself. In Scene 5, Seyton announces that the queen is dead.