The events immediately following Duncan's murder struck me as unnatural and out of place. The most obvious sign of unnatural occurrences is the fact that the Macbeths cannot seam to wash their hands clean. In nature this would have been a simple task, but yet they cannot clean their hands (or minds) of evidence of their evil deeds. Secondly the actions of people around them also is out of the ordinary, although they may be suffering from an emotional shock, they still seam quietly suspicious. The drunken porter scene, was one of my favorite parts of the play. It lightened the mood, yet never took my mind off the evilness of the events that had just occurred. Even though some people say that the porter scene is irrelevant to the play, I feel it added to the notion that there was something pernicious going on in the castle because of the reference to hell, and the drunken state of the porter.
In scene four the conversation between Ross and an old man reinforces the unnatural feeling. I thought the part about Duncan's horses tuning wild and running away was a great way to let the reader sense that nature knows what is really going on.