The light/darkness motif in regard to Lady Macbeth reveals the great change that has developed in her character by the conclusion of the play. In Act I, while she is planning Duncan's death, Lady Macbeth invokes darkness to hide the murder she intends to commit:
Come, thick night,
And pall thee in the dunnest smoke of hell,
That my keen knife see not the wound it makes,
Nor heaven peep through the blanket of the dark,
To cry "Hold, hold!"
She does not fear the darkness; it will be her help and refuge in furthering her intentions.
At the end of her life, however, shortly before her suicide, Lady Macbeth no longer welcomes the darkness. She fears it and seeks to escape from it. In Act V, Lady Macbeth walks each night in her sleep, always carrying a candle. Her attendant tells the doctor that she keeps candles burning in her room: "She has light by her continually. 'Tis her command." Exactly why Lady Macbeth is now afraid of the dark is subject to interpretation. However, night brings darkness and sleep, and it is in sleep that Lady Macbeth relives all the horrors in which she has played a part, tormented by each one.