How does Act 2 Scene 4 in Macbeth advance the plot?

Act 2 Scene 4 is a short yet an important scene, not to be
left out. The scene between Ross and the Old Man serves three important purposes and one
can easily make out how they add to the development of the
play.

a) It continues the comparison begun by Lennox in
Scene 3 between the human world and the natural
world.

 "The night has been unruly: where we lay,/ Our
chimneys were blown, and, as they say,/ Lamentings heard i'th'air, strange screams of
death/And prophesying with accents terrible/Of dire combustion and confus'd events,/ New
hatch'd to the woeful time." The old man believes that he has never in seventy years of
his life seen "hours dreadful and things strange, but this sore night hath trifled
former knowings." Further more the old man also says, 'Tis unnatural, /Even like the
deed that's done."

b) The second function of the
scene is clear when Macduff enters to bring more news" it indicates the passing of
time.

c) The scene highlights Macduff growing in greater
prominence, because it allows the audience by the tone of his voice, That Macduff
continues to be suspicious of Macbeth's involvement in the
crime.

One must also remember that Macduff's role will be
very important once Banquo will be murdered.