The setting is Gloucester's castle. Edmund betrays his father and wins Cornwall's approval by releasing the details of France's plan to aid the king. As reward, Edmund gains Gloucester's title and lands.
In this scene, both Edmund and Cornwall pretend to be virtuous, as each attempts to justify his disloyalty. Clearly, Gloucester and Lear are both victims of two self-serving men — Edmund and Cornwall. Edmund, feigning regret for having betrayed his father, laments that his nature, which is to honor his father, must now be subordinate to the loyalty he feels for his country. Thus, Edmund makes excuses for betraying his own father. Cornwall's presence serves to reinforce Edmund's choice, when he suggests that perhaps Edgar is justified to seek his father's murder. Cornwall sees Gloucester's actions as treasonous, and describes him as having a "reproveable badness" (III.5.6). This pronouncement from Cornwall endorses Edmund's treachery toward his father, and also provides Edmund with a sort of self-righteous justice.
apprehension capture or arrest.
blood parental heritage; family line; lineage.