That Macbeth and his wife “are yet but young in deed” is but a trifle. In the lines preceding this one, it is evident Macbeth has passed the point of no return, and this time, it’s not his wife who is precipitating the action. Unlike the aftermath of Macbeth’s murder of Duncan, Lady Macbeth is unable to control her husband after Banquo is slaughtered; she is forced to observe him at the dinner table while Macbeth converses with the latter’s ghost. This does not please her.
You have displaced the mirth, broke the good meeting
With most admired disorder.
Note the bitter tone of resignation: “With most admired disorder.” Lady Macbeth understands her husband is outside her sphere of influence and acidly expresses her opinion of this new man. She also summarizes how far her husband is falling, and she suspects he might fall yet further. When Ross questions Macbeth about “such sights” that he claims to behold, Lady Macbeth responds,
I pray you, speak not; he grows worse and worse;
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