In the opening of this scene Macbeth is having a banquet with some of his fellow guests. Before this scene Banquo has been killed by the murderers. Macbeth, speaking to the murderer, is saying in this scene: “But now I am cabined, cribbed, confined, bound in to saucy doubts and fears. But Banquo's safe?” By this, Macbeth is commenting and saying about how he feels uneasy that Fleance has escaped, but he keeps repeating that Banquo is "dispatched." The irony being expressed here is that he uses the word "safe" in a strange ghostly and mysterious way. Because obviously, Banquo is and isn't safe. He is safe because he's in heaven, with Duncan, away from all evils of this world and what Macbeth has turned it into by being king. Also he is dead and bloody in a trench...obviously not safe. Macbeth also describes and says, "There the grown serpent lies; the worm that's fled hath nature that in time will venom breed, no teeth for th' present." Here, he is commenting on how Banquo's death-being the grown and most dangerous serpent, is no longer a harm to Macbeth because he was killed by the murderers.  Fleance or so called, the worm, in this part escapes. Macbeth is not currently too worried about him. Since he is not in an adulthood stage and also not considered as dangerous as his father (aka Duncan) was, although Fleance will be a threat to Macbeth in the future. This scene is the highlight of the act or play and also the peak and the climax of this act or play.  We know that Banquo's ghost is sitting in the chair which was not reserved for Banquo, but was reserved for Macbeth, but only Macbeth can see the ghost causing us to have dramatic irony. The scene is bizarrely or mysteriously humorous; due to the fact, Macbeth cannot control his reaction upon seeing the ghost of Banquo. Lady Macbeth's scolds Macbeth that he is acting cowardly: “The times has been That when the brains were out, the man would die, And there an end; but now