It was an unruly night, and the owl clamored the livelong hours. Towards morning, after the accomplishment of the murder, Lady Macbeth snatched the bloody daggers from the hand of her husband to carry them back into the chamber. The air that was interrupted at the lips of the gracious Duncan seems breathless as he, appalled at the deed; and our consciousness of it sinks into an awful silence. Just then a knocking at the gate is heard.
De Quincey, in an essay "On the Knocking at the Gate," rightly notices that it reflects "back upon the murder a peculiar awfulness and depth of solemnity," and he explains this effect. "When the deed is done, when the work of darkness is perfect, then the world of darkness passes away like a pageantry in the clouds: the knocking at the gate is heard, and it makes known audibly that the reaction has commenced; the human has made its reflux upon the fiendish; the pulses of life are beginning to beat again; and the re-establishment of the goings-on of the world in which we live first makes us profoundly sensible of the awful parenthesis that had suspended them."
Admirable as this criticism is to justify the profound art of Shakspeare, it does not seem to me entirely to exhaust the effect produced by the knocking. It not only makes known to us that human life recurs, and thus emphasizes our sense of the unhuman world of murder, but it also startles us with the sudden consciousness that the human which thus recurs does it in entire ignorance of the scene at which it knocks. That makes us catch our breath, to feel how thoughtlessly life is about to stumble into the tremendous scene. What a contrast of innocent unconsciousness,--so innocent, so remote from the event, that we should think it was impertinent if our pity for the shock it brings upon itself did not prevail! We wonder who will first discover what has occurred, whether man or woman; somebody is doomed to blunder into the ghastliness of that room where Macbeth murdered sleep. What will be the sensation that thrills from the inhospitable bed around which the angels of honor and loyalty ought to have watched with spotless wings? Some one steps into this pool where all the safeguards and trusts of human life lie drenched. How will he manage to escape from it, and will the tongue be palsied "with the act of fear" to refuse to the lips words adequate to express the villainy? And yet this must be done.