The reader or audience knows something the character ignores, and so the character's words and deeds take on a meaning that the character does not perceive.
In Romeo and Juliet
My heart is wondrous light / Since this same wayward girl is so reclaimed.
Capulet speaks of his "heart" being "wonderfully light" and of the daughter who has "mended her ways." The audience knows Juliet feigned obedience to carry out the potion plan, so the father's relief sounds cruel.
Act IV: The potion of apparent death, Capulet
Death is my son-in-law, Death is my heir
Act IV: The potion of apparent death, Capulet
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