Lady Macbeth's guilt catches up to her in Act V, as detailed in the famous sleep walking scene. One of her attendants tells Macbeth of his wife's strange nocturnal behavior:
I have seen her rise from her bed, throw her nightgown upon her, unlock her closet, take forth paper, fold it, write upon 't, read it, afterwards seal it, and again return to bed; yet all this while in a most fast sleep.
We are not told what exactly she writes. A confession, perhaps? Clearly, something deep in Lady Macbeth's subconscious disturbs her sleep and prompts her odd behavior.
Her guilt becomes very clear later in the scene when she is observed walking and talking in her sleep, rubbing her hands, seeming to wash them. However, there are earlier signs that Lady Macbeth was not completely hardened to the acts she performed in the name of ambition. It had been her intention to murder Duncan herself, but when the time came, she was unable to kill him: "Had he [Duncan] not resembled / My father as he slept, I had done't." This offers an interesting insight into Lady Macbeth's character. Had she been a loving daughter? Had her father expected better of her than the conduct she was now embracing? Something in Duncan's appearance, vulnerable in his sleep, stirs her conscience.
When Macbeth returns from Duncan's chamber, so shaken by the murder he still carries the bloody daggers, Lady Macbeth resumes her cold demeanor and castigates him for his fear: "Give me the daggers. The sleeping and the dead / Are but as pictures." Her remonstrance lacks credibility. She protests too much. Only moments before, she had related to King Duncan as far more than a picture as he slept. She buries her guilt, but it resurfaces with a vengeance at the conclusion of the play.